Merge branch 'bpf-blinding'

Daniel Borkmann says:

====================
BPF updates

This set implements constant blinding for BPF, first couple of
patches are some preparatory cleanups, followed by the blinding.
Please see individual patches for details.

Thanks a lot!
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/sysctl/net.txt

@@ -43,6 +43,17 @@ Values :
 	1 - enable the JIT
 	2 - enable the JIT and ask the compiler to emit traces on kernel log.
 
+bpf_jit_harden
+--------------
+
+This enables hardening for the Berkeley Packet Filter Just in Time compiler.
+Supported are eBPF JIT backends. Enabling hardening trades off performance,
+but can mitigate JIT spraying.
+Values :
+	0 - disable JIT hardening (default value)
+	1 - enable JIT hardening for unprivileged users only
+	2 - enable JIT hardening for all users
+
 dev_weight
 --------------
 

arch/arm/Kconfig

@@ -41,7 +41,7 @@ config ARM
 	select HAVE_ARCH_SECCOMP_FILTER if (AEABI && !OABI_COMPAT)
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ARM_SMCCC if CPU_V7
-	select HAVE_BPF_JIT
+	select HAVE_CBPF_JIT
 	select HAVE_CC_STACKPROTECTOR
 	select HAVE_CONTEXT_TRACKING
 	select HAVE_C_RECORDMCOUNT

arch/arm64/Kconfig

@@ -58,7 +58,7 @@ config ARM64
 	select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_TRACEHOOK
-	select HAVE_BPF_JIT
+	select HAVE_EBPF_JIT
 	select HAVE_C_RECORDMCOUNT
 	select HAVE_CC_STACKPROTECTOR
 	select HAVE_CMPXCHG_DOUBLE

arch/arm64/net/bpf_jit_comp.c

@@ -31,8 +31,8 @@
 
 int bpf_jit_enable __read_mostly;
 
-#define TMP_REG_1 (MAX_BPF_REG + 0)
-#define TMP_REG_2 (MAX_BPF_REG + 1)
+#define TMP_REG_1 (MAX_BPF_JIT_REG + 0)
+#define TMP_REG_2 (MAX_BPF_JIT_REG + 1)
 
 /* Map BPF registers to A64 registers */
 static const int bpf2a64[] = {
@@ -54,6 +54,8 @@ static const int bpf2a64[] = {
 	/* temporary register for internal BPF JIT */
 	[TMP_REG_1] = A64_R(23),
 	[TMP_REG_2] = A64_R(24),
+	/* temporary register for blinding constants */
+	[BPF_REG_AX] = A64_R(9),
 };
 
 struct jit_ctx {
@@ -762,31 +764,45 @@ void bpf_jit_compile(struct bpf_prog *prog)
 	/* Nothing to do here. We support Internal BPF. */
 }
 
-void bpf_int_jit_compile(struct bpf_prog *prog)
+struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 {
+	struct bpf_prog *tmp, *orig_prog = prog;
 	struct bpf_binary_header *header;
+	bool tmp_blinded = false;
 	struct jit_ctx ctx;
 	int image_size;
 	u8 *image_ptr;
 
 	if (!bpf_jit_enable)
-		return;
+		return orig_prog;
 
-	if (!prog || !prog->len)
-		return;
+	tmp = bpf_jit_blind_constants(prog);
+	/* If blinding was requested and we failed during blinding,
+	 * we must fall back to the interpreter.
+	 */
+	if (IS_ERR(tmp))
+		return orig_prog;
+	if (tmp != prog) {
+		tmp_blinded = true;
+		prog = tmp;
+	}
 
 	memset(&ctx, 0, sizeof(ctx));
 	ctx.prog = prog;
 
 	ctx.offset = kcalloc(prog->len, sizeof(int), GFP_KERNEL);
-	if (ctx.offset == NULL)
-		return;
+	if (ctx.offset == NULL) {
+		prog = orig_prog;
+		goto out;
+	}
 
 	/* 1. Initial fake pass to compute ctx->idx. */
 
 	/* Fake pass to fill in ctx->offset and ctx->tmp_used. */
-	if (build_body(&ctx))
-		goto out;
+	if (build_body(&ctx)) {
+		prog = orig_prog;
+		goto out_off;
+	}
 
 	build_prologue(&ctx);
 
@@ -797,8 +813,10 @@ void bpf_int_jit_compile(struct bpf_prog *prog)
 	image_size = sizeof(u32) * ctx.idx;
 	header = bpf_jit_binary_alloc(image_size, &image_ptr,
 				      sizeof(u32), jit_fill_hole);
-	if (header == NULL)
-		goto out;
+	if (header == NULL) {
+		prog = orig_prog;
+		goto out_off;
+	}
 
 	/* 2. Now, the actual pass. */
 
@@ -809,7 +827,8 @@ void bpf_int_jit_compile(struct bpf_prog *prog)
 
 	if (build_body(&ctx)) {
 		bpf_jit_binary_free(header);
-		goto out;
+		prog = orig_prog;
+		goto out_off;
 	}
 
 	build_epilogue(&ctx);
@@ -817,7 +836,8 @@ void bpf_int_jit_compile(struct bpf_prog *prog)
 	/* 3. Extra pass to validate JITed code. */
 	if (validate_code(&ctx)) {
 		bpf_jit_binary_free(header);
-		goto out;
+		prog = orig_prog;
+		goto out_off;
 	}
 
 	/* And we're done. */
@@ -829,8 +849,14 @@ void bpf_int_jit_compile(struct bpf_prog *prog)
 	set_memory_ro((unsigned long)header, header->pages);
 	prog->bpf_func = (void *)ctx.image;
 	prog->jited = 1;
-out:
+
+out_off:
 	kfree(ctx.offset);
+out:
+	if (tmp_blinded)
+		bpf_jit_prog_release_other(prog, prog == orig_prog ?
+					   tmp : orig_prog);
+	return prog;
 }
 
 void bpf_jit_free(struct bpf_prog *prog)

arch/mips/Kconfig

@@ -15,7 +15,7 @@ config MIPS
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_TRACEHOOK
-	select HAVE_BPF_JIT if !CPU_MICROMIPS
+	select HAVE_CBPF_JIT if !CPU_MICROMIPS
 	select HAVE_FUNCTION_TRACER
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_FTRACE_MCOUNT_RECORD

arch/powerpc/Kconfig

@@ -126,7 +126,7 @@ config PPC
 	select IRQ_FORCED_THREADING
 	select HAVE_RCU_TABLE_FREE if SMP
 	select HAVE_SYSCALL_TRACEPOINTS
-	select HAVE_BPF_JIT
+	select HAVE_CBPF_JIT
 	select HAVE_ARCH_JUMP_LABEL
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select ARCH_HAS_GCOV_PROFILE_ALL

arch/s390/Kconfig

@@ -126,7 +126,7 @@ config S390
 	select HAVE_ARCH_SOFT_DIRTY
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE
-	select HAVE_BPF_JIT if PACK_STACK && HAVE_MARCH_Z196_FEATURES
+	select HAVE_EBPF_JIT if PACK_STACK && HAVE_MARCH_Z196_FEATURES
 	select HAVE_CMPXCHG_DOUBLE
 	select HAVE_CMPXCHG_LOCAL
 	select HAVE_DEBUG_KMEMLEAK

arch/s390/net/bpf_jit_comp.c

@@ -54,16 +54,17 @@ struct bpf_jit {
 #define SEEN_FUNC	16	/* calls C functions */
 #define SEEN_TAIL_CALL	32	/* code uses tail calls */
 #define SEEN_SKB_CHANGE	64	/* code changes skb data */
+#define SEEN_REG_AX	128	/* code uses constant blinding */
 #define SEEN_STACK	(SEEN_FUNC | SEEN_MEM | SEEN_SKB)
 
 /*
  * s390 registers
  */
-#define REG_W0		(__MAX_BPF_REG+0)	/* Work register 1 (even) */
-#define REG_W1		(__MAX_BPF_REG+1)	/* Work register 2 (odd) */
-#define REG_SKB_DATA	(__MAX_BPF_REG+2)	/* SKB data register */
-#define REG_L		(__MAX_BPF_REG+3)	/* Literal pool register */
-#define REG_15		(__MAX_BPF_REG+4)	/* Register 15 */
+#define REG_W0		(MAX_BPF_JIT_REG + 0)	/* Work register 1 (even) */
+#define REG_W1		(MAX_BPF_JIT_REG + 1)	/* Work register 2 (odd) */
+#define REG_SKB_DATA	(MAX_BPF_JIT_REG + 2)	/* SKB data register */
+#define REG_L		(MAX_BPF_JIT_REG + 3)	/* Literal pool register */
+#define REG_15		(MAX_BPF_JIT_REG + 4)	/* Register 15 */
 #define REG_0		REG_W0			/* Register 0 */
 #define REG_1		REG_W1			/* Register 1 */
 #define REG_2		BPF_REG_1		/* Register 2 */
@@ -88,6 +89,8 @@ static const int reg2hex[] = {
 	[BPF_REG_9]	= 10,
 	/* BPF stack pointer */
 	[BPF_REG_FP]	= 13,
+	/* Register for blinding (shared with REG_SKB_DATA) */
+	[BPF_REG_AX]	= 12,
 	/* SKB data pointer */
 	[REG_SKB_DATA]	= 12,
 	/* Work registers for s390x backend */
@@ -385,7 +388,7 @@ static void save_restore_regs(struct bpf_jit *jit, int op)
 /*
  * For SKB access %b1 contains the SKB pointer. For "bpf_jit.S"
  * we store the SKB header length on the stack and the SKB data
- * pointer in REG_SKB_DATA.
+ * pointer in REG_SKB_DATA if BPF_REG_AX is not used.
  */
 static void emit_load_skb_data_hlen(struct bpf_jit *jit)
 {
@@ -397,9 +400,10 @@ static void emit_load_skb_data_hlen(struct bpf_jit *jit)
 		   offsetof(struct sk_buff, data_len));
 	/* stg %w1,ST_OFF_HLEN(%r0,%r15) */
 	EMIT6_DISP_LH(0xe3000000, 0x0024, REG_W1, REG_0, REG_15, STK_OFF_HLEN);
-	/* lg %skb_data,data_off(%b1) */
-	EMIT6_DISP_LH(0xe3000000, 0x0004, REG_SKB_DATA, REG_0,
-		      BPF_REG_1, offsetof(struct sk_buff, data));
+	if (!(jit->seen & SEEN_REG_AX))
+		/* lg %skb_data,data_off(%b1) */
+		EMIT6_DISP_LH(0xe3000000, 0x0004, REG_SKB_DATA, REG_0,
+			      BPF_REG_1, offsetof(struct sk_buff, data));
 }
 
 /*
@@ -487,6 +491,8 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i
 	s32 imm = insn->imm;
 	s16 off = insn->off;
 
+	if (dst_reg == BPF_REG_AX || src_reg == BPF_REG_AX)
+		jit->seen |= SEEN_REG_AX;
 	switch (insn->code) {
 	/*
 	 * BPF_MOV
@@ -1188,7 +1194,7 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i
 		/*
 		 * Implicit input:
 		 *  BPF_REG_6	 (R7) : skb pointer
-		 *  REG_SKB_DATA (R12): skb data pointer
+		 *  REG_SKB_DATA (R12): skb data pointer (if no BPF_REG_AX)
 		 *
 		 * Calculated input:
 		 *  BPF_REG_2	 (R3) : offset of byte(s) to fetch in skb
@@ -1209,6 +1215,11 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i
 			/* agfr %b2,%src (%src is s32 here) */
 			EMIT4(0xb9180000, BPF_REG_2, src_reg);
 
+		/* Reload REG_SKB_DATA if BPF_REG_AX is used */
+		if (jit->seen & SEEN_REG_AX)
+			/* lg %skb_data,data_off(%b6) */
+			EMIT6_DISP_LH(0xe3000000, 0x0004, REG_SKB_DATA, REG_0,
+				      BPF_REG_6, offsetof(struct sk_buff, data));
 		/* basr %b5,%w1 (%b5 is call saved) */
 		EMIT2(0x0d00, BPF_REG_5, REG_W1);
 
@@ -1262,37 +1273,62 @@ void bpf_jit_compile(struct bpf_prog *fp)
 /*
  * Compile eBPF program "fp"
  */
-void bpf_int_jit_compile(struct bpf_prog *fp)
+struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
 {
+	struct bpf_prog *tmp, *orig_fp = fp;
 	struct bpf_binary_header *header;
+	bool tmp_blinded = false;
 	struct bpf_jit jit;
 	int pass;
 
 	if (!bpf_jit_enable)
-		return;
+		return orig_fp;
+
+	tmp = bpf_jit_blind_constants(fp);
+	/*
+	 * If blinding was requested and we failed during blinding,
+	 * we must fall back to the interpreter.
+	 */
+	if (IS_ERR(tmp))
+		return orig_fp;
+	if (tmp != fp) {
+		tmp_blinded = true;
+		fp = tmp;
+	}
+
 	memset(&jit, 0, sizeof(jit));
 	jit.addrs = kcalloc(fp->len + 1, sizeof(*jit.addrs), GFP_KERNEL);
-	if (jit.addrs == NULL)
-		return;
+	if (jit.addrs == NULL) {
+		fp = orig_fp;
+		goto out;
+	}
 	/*
 	 * Three initial passes:
 	 *   - 1/2: Determine clobbered registers
 	 *   - 3:   Calculate program size and addrs arrray
 	 */
 	for (pass = 1; pass <= 3; pass++) {
-		if (bpf_jit_prog(&jit, fp))
+		if (bpf_jit_prog(&jit, fp)) {
+			fp = orig_fp;
 			goto free_addrs;
+		}
 	}
 	/*
 	 * Final pass: Allocate and generate program
 	 */
-	if (jit.size >= BPF_SIZE_MAX)
+	if (jit.size >= BPF_SIZE_MAX) {
+		fp = orig_fp;
 		goto free_addrs;
+	}
 	header = bpf_jit_binary_alloc(jit.size, &jit.prg_buf, 2, jit_fill_hole);
-	if (!header)
+	if (!header) {
+		fp = orig_fp;
 		goto free_addrs;
-	if (bpf_jit_prog(&jit, fp))
+	}
+	if (bpf_jit_prog(&jit, fp)) {
+		fp = orig_fp;
 		goto free_addrs;
+	}
 	if (bpf_jit_enable > 1) {
 		bpf_jit_dump(fp->len, jit.size, pass, jit.prg_buf);
 		if (jit.prg_buf)
@@ -1305,6 +1341,11 @@ void bpf_int_jit_compile(struct bpf_prog *fp)
 	}
 free_addrs:
 	kfree(jit.addrs);
+out:
+	if (tmp_blinded)
+		bpf_jit_prog_release_other(fp, fp == orig_fp ?
+					   tmp : orig_fp);
+	return fp;
 }
 
 /*

arch/sparc/Kconfig

@@ -32,7 +32,7 @@ config SPARC
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select GENERIC_PCI_IOMAP
 	select HAVE_NMI_WATCHDOG if SPARC64
-	select HAVE_BPF_JIT
+	select HAVE_CBPF_JIT
 	select HAVE_DEBUG_BUGVERBOSE
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_CLOCKEVENTS

arch/x86/Kconfig

@@ -91,7 +91,7 @@ config X86
 	select HAVE_ARCH_SOFT_DIRTY		if X86_64
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE
-	select HAVE_BPF_JIT			if X86_64
+	select HAVE_EBPF_JIT			if X86_64
 	select HAVE_CC_STACKPROTECTOR
 	select HAVE_CMPXCHG_DOUBLE
 	select HAVE_CMPXCHG_LOCAL

arch/x86/net/bpf_jit_comp.c

@@ -110,11 +110,16 @@ static void bpf_flush_icache(void *start, void *end)
 	((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
 
 /* pick a register outside of BPF range for JIT internal work */
-#define AUX_REG (MAX_BPF_REG + 1)
+#define AUX_REG (MAX_BPF_JIT_REG + 1)
 
-/* the following table maps BPF registers to x64 registers.
- * x64 register r12 is unused, since if used as base address register
- * in load/store instructions, it always needs an extra byte of encoding
+/* The following table maps BPF registers to x64 registers.
+ *
+ * x64 register r12 is unused, since if used as base address
+ * register in load/store instructions, it always needs an
+ * extra byte of encoding and is callee saved.
+ *
+ *  r9 caches skb->len - skb->data_len
+ * r10 caches skb->data, and used for blinding (if enabled)
  */
 static const int reg2hex[] = {
 	[BPF_REG_0] = 0,  /* rax */
@@ -128,6 +133,7 @@ static const int reg2hex[] = {
 	[BPF_REG_8] = 6,  /* r14 callee saved */
 	[BPF_REG_9] = 7,  /* r15 callee saved */
 	[BPF_REG_FP] = 5, /* rbp readonly */
+	[BPF_REG_AX] = 2, /* r10 temp register */
 	[AUX_REG] = 3,    /* r11 temp register */
 };
 
@@ -141,7 +147,8 @@ static bool is_ereg(u32 reg)
 			     BIT(AUX_REG) |
 			     BIT(BPF_REG_7) |
 			     BIT(BPF_REG_8) |
-			     BIT(BPF_REG_9));
+			     BIT(BPF_REG_9) |
+			     BIT(BPF_REG_AX));
 }
 
 /* add modifiers if 'reg' maps to x64 registers r8..r15 */
@@ -182,6 +189,7 @@ static void jit_fill_hole(void *area, unsigned int size)
 struct jit_context {
 	int cleanup_addr; /* epilogue code offset */
 	bool seen_ld_abs;
+	bool seen_ax_reg;
 };
 
 /* maximum number of bytes emitted while JITing one eBPF insn */
@@ -345,6 +353,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
 	struct bpf_insn *insn = bpf_prog->insnsi;
 	int insn_cnt = bpf_prog->len;
 	bool seen_ld_abs = ctx->seen_ld_abs | (oldproglen == 0);
+	bool seen_ax_reg = ctx->seen_ax_reg | (oldproglen == 0);
 	bool seen_exit = false;
 	u8 temp[BPF_MAX_INSN_SIZE + BPF_INSN_SAFETY];
 	int i, cnt = 0;
@@ -367,6 +376,9 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
 		int ilen;
 		u8 *func;
 
+		if (dst_reg == BPF_REG_AX || src_reg == BPF_REG_AX)
+			ctx->seen_ax_reg = seen_ax_reg = true;
+
 		switch (insn->code) {
 			/* ALU */
 		case BPF_ALU | BPF_ADD | BPF_X:
@@ -1002,6 +1014,10 @@ xadd:			if (is_imm8(insn->off))
 			 * sk_load_* helpers also use %r10 and %r9d.
 			 * See bpf_jit.S
 			 */
+			if (seen_ax_reg)
+				/* r10 = skb->data, mov %r10, off32(%rbx) */
+				EMIT3_off32(0x4c, 0x8b, 0x93,
+					    offsetof(struct sk_buff, data));
 			EMIT1_off32(0xE8, jmp_offset); /* call */
 			break;
 
@@ -1073,25 +1089,37 @@ void bpf_jit_compile(struct bpf_prog *prog)
 {
 }
 
-void bpf_int_jit_compile(struct bpf_prog *prog)
+struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 {
 	struct bpf_binary_header *header = NULL;
+	struct bpf_prog *tmp, *orig_prog = prog;
 	int proglen, oldproglen = 0;
 	struct jit_context ctx = {};
+	bool tmp_blinded = false;
 	u8 *image = NULL;
 	int *addrs;
 	int pass;
 	int i;
 
 	if (!bpf_jit_enable)
-		return;
+		return orig_prog;
 
-	if (!prog || !prog->len)
-		return;
+	tmp = bpf_jit_blind_constants(prog);
+	/* If blinding was requested and we failed during blinding,
+	 * we must fall back to the interpreter.
+	 */
+	if (IS_ERR(tmp))
+		return orig_prog;
+	if (tmp != prog) {
+		tmp_blinded = true;
+		prog = tmp;
+	}
 
 	addrs = kmalloc(prog->len * sizeof(*addrs), GFP_KERNEL);
-	if (!addrs)
-		return;
+	if (!addrs) {
+		prog = orig_prog;
+		goto out;
+	}
 
 	/* Before first pass, make a rough estimation of addrs[]
 	 * each bpf instruction is translated to less than 64 bytes
@@ -1113,21 +1141,25 @@ void bpf_int_jit_compile(struct bpf_prog *prog)
 			image = NULL;
 			if (header)
 				bpf_jit_binary_free(header);
-			goto out;
+			prog = orig_prog;
+			goto out_addrs;
 		}
 		if (image) {
 			if (proglen != oldproglen) {
 				pr_err("bpf_jit: proglen=%d != oldproglen=%d\n",
 				       proglen, oldproglen);
-				goto out;
+				prog = orig_prog;
+				goto out_addrs;
 			}
 			break;
 		}
 		if (proglen == oldproglen) {
 			header = bpf_jit_binary_alloc(proglen, &image,
 						      1, jit_fill_hole);
-			if (!header)
-				goto out;
+			if (!header) {
+				prog = orig_prog;
+				goto out_addrs;
+			}
 		}
 		oldproglen = proglen;
 	}
@@ -1141,8 +1173,14 @@ void bpf_int_jit_compile(struct bpf_prog *prog)
 		prog->bpf_func = (void *)image;
 		prog->jited = 1;
 	}
-out:
+
+out_addrs:
 	kfree(addrs);
+out:
+	if (tmp_blinded)
+		bpf_jit_prog_release_other(prog, prog == orig_prog ?
+					   tmp : orig_prog);
+	return prog;
 }
 
 void bpf_jit_free(struct bpf_prog *fp)

include/linux/filter.h

@@ -13,6 +13,8 @@
 #include <linux/printk.h>
 #include <linux/workqueue.h>
 #include <linux/sched.h>
+#include <linux/capability.h>
+
 #include <net/sch_generic.h>
 
 #include <asm/cacheflush.h>
@@ -42,6 +44,15 @@ struct bpf_prog_aux;
 #define BPF_REG_X	BPF_REG_7
 #define BPF_REG_TMP	BPF_REG_8
 
+/* Kernel hidden auxiliary/helper register for hardening step.
+ * Only used by eBPF JITs. It's nothing more than a temporary
+ * register that JITs use internally, only that here it's part
+ * of eBPF instructions that have been rewritten for blinding
+ * constants. See JIT pre-step in bpf_jit_blind_constants().
+ */
+#define BPF_REG_AX		MAX_BPF_REG
+#define MAX_BPF_JIT_REG		(MAX_BPF_REG + 1)
+
 /* BPF program can access up to 512 bytes of stack space. */
 #define MAX_BPF_STACK	512
 
@@ -458,7 +469,7 @@ static inline void bpf_prog_unlock_ro(struct bpf_prog *fp)
 
 int sk_filter(struct sock *sk, struct sk_buff *skb);
 
-int bpf_prog_select_runtime(struct bpf_prog *fp);
+struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err);
 void bpf_prog_free(struct bpf_prog *fp);
 
 struct bpf_prog *bpf_prog_alloc(unsigned int size, gfp_t gfp_extra_flags);
@@ -492,10 +503,17 @@ bool sk_filter_charge(struct sock *sk, struct sk_filter *fp);
 void sk_filter_uncharge(struct sock *sk, struct sk_filter *fp);
 
 u64 __bpf_call_base(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
-void bpf_int_jit_compile(struct bpf_prog *fp);
+
+struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog);
 bool bpf_helper_changes_skb_data(void *func);
 
+struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
+				       const struct bpf_insn *patch, u32 len);
+
 #ifdef CONFIG_BPF_JIT
+extern int bpf_jit_enable;
+extern int bpf_jit_harden;
+
 typedef void (*bpf_jit_fill_hole_t)(void *area, unsigned int size);
 
 struct bpf_binary_header *
@@ -507,6 +525,9 @@ void bpf_jit_binary_free(struct bpf_binary_header *hdr);
 void bpf_jit_compile(struct bpf_prog *fp);
 void bpf_jit_free(struct bpf_prog *fp);
 
+struct bpf_prog *bpf_jit_blind_constants(struct bpf_prog *fp);
+void bpf_jit_prog_release_other(struct bpf_prog *fp, struct bpf_prog *fp_other);
+
 static inline void bpf_jit_dump(unsigned int flen, unsigned int proglen,
 				u32 pass, void *image)
 {
@@ -517,6 +538,33 @@ static inline void bpf_jit_dump(unsigned int flen, unsigned int proglen,
 		print_hex_dump(KERN_ERR, "JIT code: ", DUMP_PREFIX_OFFSET,
 			       16, 1, image, proglen, false);
 }
+
+static inline bool bpf_jit_is_ebpf(void)
+{
+# ifdef CONFIG_HAVE_EBPF_JIT
+	return true;
+# else
+	return false;
+# endif
+}
+
+static inline bool bpf_jit_blinding_enabled(void)
+{
+	/* These are the prerequisites, should someone ever have the
+	 * idea to call blinding outside of them, we make sure to
+	 * bail out.
+	 */
+	if (!bpf_jit_is_ebpf())
+		return false;
+	if (!bpf_jit_enable)
+		return false;
+	if (!bpf_jit_harden)
+		return false;
+	if (bpf_jit_harden == 1 && capable(CAP_SYS_ADMIN))
+		return false;
+
+	return true;
+}
 #else
 static inline void bpf_jit_compile(struct bpf_prog *fp)
 {

include/linux/netdevice.h

@@ -3759,7 +3759,6 @@ void netdev_stats_to_stats64(struct rtnl_link_stats64 *stats64,
 extern int		netdev_max_backlog;
 extern int		netdev_tstamp_prequeue;
 extern int		weight_p;
-extern int		bpf_jit_enable;
 
 bool netdev_has_upper_dev(struct net_device *dev, struct net_device *upper_dev);
 struct net_device *netdev_upper_get_next_dev_rcu(struct net_device *dev,

kernel/bpf/core.c

@@ -129,14 +129,83 @@ struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size,
 
 	return fp;
 }
-EXPORT_SYMBOL_GPL(bpf_prog_realloc);
 
 void __bpf_prog_free(struct bpf_prog *fp)
 {
 	kfree(fp->aux);
 	vfree(fp);
 }
-EXPORT_SYMBOL_GPL(__bpf_prog_free);
+
+static bool bpf_is_jmp_and_has_target(const struct bpf_insn *insn)
+{
+	return BPF_CLASS(insn->code) == BPF_JMP  &&
+	       /* Call and Exit are both special jumps with no
+		* target inside the BPF instruction image.
+		*/
+	       BPF_OP(insn->code) != BPF_CALL &&
+	       BPF_OP(insn->code) != BPF_EXIT;
+}
+
+static void bpf_adj_branches(struct bpf_prog *prog, u32 pos, u32 delta)
+{
+	struct bpf_insn *insn = prog->insnsi;
+	u32 i, insn_cnt = prog->len;
+
+	for (i = 0; i < insn_cnt; i++, insn++) {
+		if (!bpf_is_jmp_and_has_target(insn))
+			continue;
+
+		/* Adjust offset of jmps if we cross boundaries. */
+		if (i < pos && i + insn->off + 1 > pos)
+			insn->off += delta;
+		else if (i > pos + delta && i + insn->off + 1 <= pos + delta)
+			insn->off -= delta;
+	}
+}
+
+struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
+				       const struct bpf_insn *patch, u32 len)
+{
+	u32 insn_adj_cnt, insn_rest, insn_delta = len - 1;
+	struct bpf_prog *prog_adj;
+
+	/* Since our patchlet doesn't expand the image, we're done. */
+	if (insn_delta == 0) {
+		memcpy(prog->insnsi + off, patch, sizeof(*patch));
+		return prog;
+	}
+
+	insn_adj_cnt = prog->len + insn_delta;
+
+	/* Several new instructions need to be inserted. Make room
+	 * for them. Likely, there's no need for a new allocation as
+	 * last page could have large enough tailroom.
+	 */
+	prog_adj = bpf_prog_realloc(prog, bpf_prog_size(insn_adj_cnt),
+				    GFP_USER);
+	if (!prog_adj)
+		return NULL;
+
+	prog_adj->len = insn_adj_cnt;
+
+	/* Patching happens in 3 steps:
+	 *
+	 * 1) Move over tail of insnsi from next instruction onwards,
+	 *    so we can patch the single target insn with one or more
+	 *    new ones (patching is always from 1 to n insns, n > 0).
+	 * 2) Inject new instructions at the target location.
+	 * 3) Adjust branch offsets if necessary.
+	 */
+	insn_rest = insn_adj_cnt - off - len;
+
+	memmove(prog_adj->insnsi + off + len, prog_adj->insnsi + off + 1,
+		sizeof(*patch) * insn_rest);
+	memcpy(prog_adj->insnsi + off, patch, sizeof(*patch) * len);
+
+	bpf_adj_branches(prog_adj, off, insn_delta);
+
+	return prog_adj;
+}
 
 #ifdef CONFIG_BPF_JIT
 struct bpf_binary_header *
@@ -174,6 +243,209 @@ void bpf_jit_binary_free(struct bpf_binary_header *hdr)
 {
 	module_memfree(hdr);
 }
+
+int bpf_jit_harden __read_mostly;
+
+static int bpf_jit_blind_insn(const struct bpf_insn *from,
+			      const struct bpf_insn *aux,
+			      struct bpf_insn *to_buff)
+{
+	struct bpf_insn *to = to_buff;
+	u32 imm_rnd = prandom_u32();
+	s16 off;
+
+	BUILD_BUG_ON(BPF_REG_AX  + 1 != MAX_BPF_JIT_REG);
+	BUILD_BUG_ON(MAX_BPF_REG + 1 != MAX_BPF_JIT_REG);
+
+	if (from->imm == 0 &&
+	    (from->code == (BPF_ALU   | BPF_MOV | BPF_K) ||
+	     from->code == (BPF_ALU64 | BPF_MOV | BPF_K))) {
+		*to++ = BPF_ALU64_REG(BPF_XOR, from->dst_reg, from->dst_reg);
+		goto out;
+	}
+
+	switch (from->code) {
+	case BPF_ALU | BPF_ADD | BPF_K:
+	case BPF_ALU | BPF_SUB | BPF_K:
+	case BPF_ALU | BPF_AND | BPF_K:
+	case BPF_ALU | BPF_OR  | BPF_K:
+	case BPF_ALU | BPF_XOR | BPF_K:
+	case BPF_ALU | BPF_MUL | BPF_K:
+	case BPF_ALU | BPF_MOV | BPF_K:
+	case BPF_ALU | BPF_DIV | BPF_K:
+	case BPF_ALU | BPF_MOD | BPF_K:
+		*to++ = BPF_ALU32_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ from->imm);
+		*to++ = BPF_ALU32_IMM(BPF_XOR, BPF_REG_AX, imm_rnd);
+		*to++ = BPF_ALU32_REG(from->code, from->dst_reg, BPF_REG_AX);
+		break;
+
+	case BPF_ALU64 | BPF_ADD | BPF_K:
+	case BPF_ALU64 | BPF_SUB | BPF_K:
+	case BPF_ALU64 | BPF_AND | BPF_K:
+	case BPF_ALU64 | BPF_OR  | BPF_K:
+	case BPF_ALU64 | BPF_XOR | BPF_K:
+	case BPF_ALU64 | BPF_MUL | BPF_K:
+	case BPF_ALU64 | BPF_MOV | BPF_K:
+	case BPF_ALU64 | BPF_DIV | BPF_K:
+	case BPF_ALU64 | BPF_MOD | BPF_K:
+		*to++ = BPF_ALU64_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ from->imm);
+		*to++ = BPF_ALU64_IMM(BPF_XOR, BPF_REG_AX, imm_rnd);
+		*to++ = BPF_ALU64_REG(from->code, from->dst_reg, BPF_REG_AX);
+		break;
+
+	case BPF_JMP | BPF_JEQ  | BPF_K:
+	case BPF_JMP | BPF_JNE  | BPF_K:
+	case BPF_JMP | BPF_JGT  | BPF_K:
+	case BPF_JMP | BPF_JGE  | BPF_K:
+	case BPF_JMP | BPF_JSGT | BPF_K:
+	case BPF_JMP | BPF_JSGE | BPF_K:
+	case BPF_JMP | BPF_JSET | BPF_K:
+		/* Accommodate for extra offset in case of a backjump. */
+		off = from->off;
+		if (off < 0)
+			off -= 2;
+		*to++ = BPF_ALU64_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ from->imm);
+		*to++ = BPF_ALU64_IMM(BPF_XOR, BPF_REG_AX, imm_rnd);
+		*to++ = BPF_JMP_REG(from->code, from->dst_reg, BPF_REG_AX, off);
+		break;
+
+	case BPF_LD | BPF_ABS | BPF_W:
+	case BPF_LD | BPF_ABS | BPF_H:
+	case BPF_LD | BPF_ABS | BPF_B:
+		*to++ = BPF_ALU64_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ from->imm);
+		*to++ = BPF_ALU64_IMM(BPF_XOR, BPF_REG_AX, imm_rnd);
+		*to++ = BPF_LD_IND(from->code, BPF_REG_AX, 0);
+		break;
+
+	case BPF_LD | BPF_IND | BPF_W:
+	case BPF_LD | BPF_IND | BPF_H:
+	case BPF_LD | BPF_IND | BPF_B:
+		*to++ = BPF_ALU64_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ from->imm);
+		*to++ = BPF_ALU64_IMM(BPF_XOR, BPF_REG_AX, imm_rnd);
+		*to++ = BPF_ALU32_REG(BPF_ADD, BPF_REG_AX, from->src_reg);
+		*to++ = BPF_LD_IND(from->code, BPF_REG_AX, 0);
+		break;
+
+	case BPF_LD | BPF_IMM | BPF_DW:
+		*to++ = BPF_ALU64_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ aux[1].imm);
+		*to++ = BPF_ALU64_IMM(BPF_XOR, BPF_REG_AX, imm_rnd);
+		*to++ = BPF_ALU64_IMM(BPF_LSH, BPF_REG_AX, 32);
+		*to++ = BPF_ALU64_REG(BPF_MOV, aux[0].dst_reg, BPF_REG_AX);
+		break;
+	case 0: /* Part 2 of BPF_LD | BPF_IMM | BPF_DW. */
+		*to++ = BPF_ALU32_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ aux[0].imm);
+		*to++ = BPF_ALU32_IMM(BPF_XOR, BPF_REG_AX, imm_rnd);
+		*to++ = BPF_ALU64_REG(BPF_OR,  aux[0].dst_reg, BPF_REG_AX);
+		break;
+
+	case BPF_ST | BPF_MEM | BPF_DW:
+	case BPF_ST | BPF_MEM | BPF_W:
+	case BPF_ST | BPF_MEM | BPF_H:
+	case BPF_ST | BPF_MEM | BPF_B:
+		*to++ = BPF_ALU64_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ from->imm);
+		*to++ = BPF_ALU64_IMM(BPF_XOR, BPF_REG_AX, imm_rnd);
+		*to++ = BPF_STX_MEM(from->code, from->dst_reg, BPF_REG_AX, from->off);
+		break;
+	}
+out:
+	return to - to_buff;
+}
+
+static struct bpf_prog *bpf_prog_clone_create(struct bpf_prog *fp_other,
+					      gfp_t gfp_extra_flags)
+{
+	gfp_t gfp_flags = GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO |
+			  gfp_extra_flags;
+	struct bpf_prog *fp;
+
+	fp = __vmalloc(fp_other->pages * PAGE_SIZE, gfp_flags, PAGE_KERNEL);
+	if (fp != NULL) {
+		kmemcheck_annotate_bitfield(fp, meta);
+
+		/* aux->prog still points to the fp_other one, so
+		 * when promoting the clone to the real program,
+		 * this still needs to be adapted.
+		 */
+		memcpy(fp, fp_other, fp_other->pages * PAGE_SIZE);
+	}
+
+	return fp;
+}
+
+static void bpf_prog_clone_free(struct bpf_prog *fp)
+{
+	/* aux was stolen by the other clone, so we cannot free
+	 * it from this path! It will be freed eventually by the
+	 * other program on release.
+	 *
+	 * At this point, we don't need a deferred release since
+	 * clone is guaranteed to not be locked.
+	 */
+	fp->aux = NULL;
+	__bpf_prog_free(fp);
+}
+
+void bpf_jit_prog_release_other(struct bpf_prog *fp, struct bpf_prog *fp_other)
+{
+	/* We have to repoint aux->prog to self, as we don't
+	 * know whether fp here is the clone or the original.
+	 */
+	fp->aux->prog = fp;
+	bpf_prog_clone_free(fp_other);
+}
+
+struct bpf_prog *bpf_jit_blind_constants(struct bpf_prog *prog)
+{
+	struct bpf_insn insn_buff[16], aux[2];
+	struct bpf_prog *clone, *tmp;
+	int insn_delta, insn_cnt;
+	struct bpf_insn *insn;
+	int i, rewritten;
+
+	if (!bpf_jit_blinding_enabled())
+		return prog;
+
+	clone = bpf_prog_clone_create(prog, GFP_USER);
+	if (!clone)
+		return ERR_PTR(-ENOMEM);
+
+	insn_cnt = clone->len;
+	insn = clone->insnsi;
+
+	for (i = 0; i < insn_cnt; i++, insn++) {
+		/* We temporarily need to hold the original ld64 insn
+		 * so that we can still access the first part in the
+		 * second blinding run.
+		 */
+		if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW) &&
+		    insn[1].code == 0)
+			memcpy(aux, insn, sizeof(aux));
+
+		rewritten = bpf_jit_blind_insn(insn, aux, insn_buff);
+		if (!rewritten)
+			continue;
+
+		tmp = bpf_patch_insn_single(clone, i, insn_buff, rewritten);
+		if (!tmp) {
+			/* Patching may have repointed aux->prog during
+			 * realloc from the original one, so we need to
+			 * fix it up here on error.
+			 */
+			bpf_jit_prog_release_other(prog, clone);
+			return ERR_PTR(-ENOMEM);
+		}
+
+		clone = tmp;
+		insn_delta = rewritten - 1;
+
+		/* Walk new program and skip insns we just inserted. */
+		insn = clone->insnsi + i + insn_delta;
+		insn_cnt += insn_delta;
+		i        += insn_delta;
+	}
+
+	return clone;
+}
 #endif /* CONFIG_BPF_JIT */
 
 /* Base function for offset calculation. Needs to go into .text section,
@@ -692,15 +964,22 @@ static int bpf_check_tail_call(const struct bpf_prog *fp)
 /**
  *	bpf_prog_select_runtime - select exec runtime for BPF program
  *	@fp: bpf_prog populated with internal BPF program
+ *	@err: pointer to error variable
  *
  * Try to JIT eBPF program, if JIT is not available, use interpreter.
  * The BPF program will be executed via BPF_PROG_RUN() macro.
  */
-int bpf_prog_select_runtime(struct bpf_prog *fp)
+struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err)
 {
 	fp->bpf_func = (void *) __bpf_prog_run;
 
-	bpf_int_jit_compile(fp);
+	/* eBPF JITs can rewrite the program in case constant
+	 * blinding is active. However, in case of error during
+	 * blinding, bpf_int_jit_compile() must always return a
+	 * valid program, which in this case would simply not
+	 * be JITed, but falls back to the interpreter.
+	 */
+	fp = bpf_int_jit_compile(fp);
 	bpf_prog_lock_ro(fp);
 
 	/* The tail call compatibility check can only be done at
@@ -708,7 +987,9 @@ int bpf_prog_select_runtime(struct bpf_prog *fp)
 	 * with JITed or non JITed program concatenations and not
 	 * all eBPF JITs might immediately support all features.
 	 */
-	return bpf_check_tail_call(fp);
+	*err = bpf_check_tail_call(fp);
+
+	return fp;
 }
 EXPORT_SYMBOL_GPL(bpf_prog_select_runtime);
 
@@ -790,8 +1071,9 @@ const struct bpf_func_proto bpf_tail_call_proto = {
 };
 
 /* For classic BPF JITs that don't implement bpf_int_jit_compile(). */
-void __weak bpf_int_jit_compile(struct bpf_prog *prog)
+struct bpf_prog * __weak bpf_int_jit_compile(struct bpf_prog *prog)
 {
+	return prog;
 }
 
 bool __weak bpf_helper_changes_skb_data(void *func)

kernel/bpf/syscall.c

@@ -762,7 +762,7 @@ static int bpf_prog_load(union bpf_attr *attr)
 	fixup_bpf_calls(prog);
 
 	/* eBPF program is ready to be JITed */
-	err = bpf_prog_select_runtime(prog);
+	prog = bpf_prog_select_runtime(prog, &err);
 	if (err < 0)
 		goto free_used_maps;
 

kernel/bpf/verifier.c

@@ -2587,26 +2587,6 @@ static void convert_pseudo_ld_imm64(struct verifier_env *env)
 			insn->src_reg = 0;
 }
 
-static void adjust_branches(struct bpf_prog *prog, int pos, int delta)
-{
-	struct bpf_insn *insn = prog->insnsi;
-	int insn_cnt = prog->len;
-	int i;
-
-	for (i = 0; i < insn_cnt; i++, insn++) {
-		if (BPF_CLASS(insn->code) != BPF_JMP ||
-		    BPF_OP(insn->code) == BPF_CALL ||
-		    BPF_OP(insn->code) == BPF_EXIT)
-			continue;
-
-		/* adjust offset of jmps if necessary */
-		if (i < pos && i + insn->off + 1 > pos)
-			insn->off += delta;
-		else if (i > pos + delta && i + insn->off + 1 <= pos + delta)
-			insn->off -= delta;
-	}
-}
-
 /* convert load instructions that access fields of 'struct __sk_buff'
  * into sequence of instructions that access fields of 'struct sk_buff'
  */
@@ -2616,14 +2596,15 @@ static int convert_ctx_accesses(struct verifier_env *env)
 	int insn_cnt = env->prog->len;
 	struct bpf_insn insn_buf[16];
 	struct bpf_prog *new_prog;
-	u32 cnt;
-	int i;
 	enum bpf_access_type type;
+	int i;
 
 	if (!env->prog->aux->ops->convert_ctx_access)
 		return 0;
 
 	for (i = 0; i < insn_cnt; i++, insn++) {
+		u32 insn_delta, cnt;
+
 		if (insn->code == (BPF_LDX | BPF_MEM | BPF_W))
 			type = BPF_READ;
 		else if (insn->code == (BPF_STX | BPF_MEM | BPF_W))
@@ -2645,34 +2626,18 @@ static int convert_ctx_accesses(struct verifier_env *env)
 			return -EINVAL;
 		}
 
-		if (cnt == 1) {
-			memcpy(insn, insn_buf, sizeof(*insn));
-			continue;
-		}
-
-		/* several new insns need to be inserted. Make room for them */
-		insn_cnt += cnt - 1;
-		new_prog = bpf_prog_realloc(env->prog,
-					    bpf_prog_size(insn_cnt),
-					    GFP_USER);
+		new_prog = bpf_patch_insn_single(env->prog, i, insn_buf, cnt);
 		if (!new_prog)
 			return -ENOMEM;
 
-		new_prog->len = insn_cnt;
-
-		memmove(new_prog->insnsi + i + cnt, new_prog->insns + i + 1,
-			sizeof(*insn) * (insn_cnt - i - cnt));
-
-		/* copy substitute insns in place of load instruction */
-		memcpy(new_prog->insnsi + i, insn_buf, sizeof(*insn) * cnt);
-
-		/* adjust branches in the whole program */
-		adjust_branches(new_prog, i, cnt - 1);
+		insn_delta = cnt - 1;
 
 		/* keep walking new program and skip insns we just inserted */
 		env->prog = new_prog;
-		insn = new_prog->insnsi + i + cnt - 1;
-		i += cnt - 1;
+		insn      = new_prog->insnsi + i + insn_delta;
+
+		insn_cnt += insn_delta;
+		i        += insn_delta;
 	}
 
 	return 0;

lib/test_bpf.c

@@ -5621,7 +5621,10 @@ static struct bpf_prog *generate_filter(int which, int *err)
 		fp->type = BPF_PROG_TYPE_SOCKET_FILTER;
 		memcpy(fp->insnsi, fptr, fp->len * sizeof(struct bpf_insn));
 
-		bpf_prog_select_runtime(fp);
+		/* We cannot error here as we don't need type compatibility
+		 * checks.
+		 */
+		fp = bpf_prog_select_runtime(fp, err);
 		break;
 	}
 

net/Kconfig

@@ -289,14 +289,17 @@ config BQL
 
 config BPF_JIT
 	bool "enable BPF Just In Time compiler"
-	depends on HAVE_BPF_JIT
+	depends on HAVE_CBPF_JIT || HAVE_EBPF_JIT
 	depends on MODULES
 	---help---
 	  Berkeley Packet Filter filtering capabilities are normally handled
 	  by an interpreter. This option allows kernel to generate a native
 	  code when filter is loaded in memory. This should speedup
-	  packet sniffing (libpcap/tcpdump). Note : Admin should enable
-	  this feature changing /proc/sys/net/core/bpf_jit_enable
+	  packet sniffing (libpcap/tcpdump).
+
+	  Note, admin should enable this feature changing:
+	  /proc/sys/net/core/bpf_jit_enable
+	  /proc/sys/net/core/bpf_jit_harden (optional)
 
 config NET_FLOW_LIMIT
 	bool
@@ -419,6 +422,14 @@ config MAY_USE_DEVLINK
 
 endif   # if NET
 
-# Used by archs to tell that they support BPF_JIT
-config HAVE_BPF_JIT
+# Used by archs to tell that they support BPF JIT compiler plus which flavour.
+# Only one of the two can be selected for a specific arch since eBPF JIT supersedes
+# the cBPF JIT.
+
+# Classic BPF JIT (cBPF)
+config HAVE_CBPF_JIT
+	bool
+
+# Extended BPF JIT (eBPF)
+config HAVE_EBPF_JIT
 	bool

net/core/filter.c

@@ -994,7 +994,11 @@ static struct bpf_prog *bpf_migrate_filter(struct bpf_prog *fp)
 		 */
 		goto out_err_free;
 
-	bpf_prog_select_runtime(fp);
+	/* We are guaranteed to never error here with cBPF to eBPF
+	 * transitions, since there's no issue with type compatibility
+	 * checks on program arrays.
+	 */
+	fp = bpf_prog_select_runtime(fp, &err);
 
 	kfree(old_prog);
 	return fp;
@@ -2069,16 +2073,12 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
 
 static bool __is_valid_access(int off, int size, enum bpf_access_type type)
 {
-	/* check bounds */
 	if (off < 0 || off >= sizeof(struct __sk_buff))
 		return false;
-
-	/* disallow misaligned access */
+	/* The verifier guarantees that size > 0. */
 	if (off % size != 0)
 		return false;
-
-	/* all __sk_buff fields are __u32 */
-	if (size != 4)
+	if (size != sizeof(__u32))
 		return false;
 
 	return true;
@@ -2097,7 +2097,7 @@ static bool sk_filter_is_valid_access(int off, int size,
 	if (type == BPF_WRITE) {
 		switch (off) {
 		case offsetof(struct __sk_buff, cb[0]) ...
-			offsetof(struct __sk_buff, cb[4]):
+		     offsetof(struct __sk_buff, cb[4]):
 			break;
 		default:
 			return false;
@@ -2278,30 +2278,30 @@ static u32 bpf_net_convert_ctx_access(enum bpf_access_type type, int dst_reg,
 }
 
 static const struct bpf_verifier_ops sk_filter_ops = {
-	.get_func_proto = sk_filter_func_proto,
-	.is_valid_access = sk_filter_is_valid_access,
-	.convert_ctx_access = bpf_net_convert_ctx_access,
+	.get_func_proto		= sk_filter_func_proto,
+	.is_valid_access	= sk_filter_is_valid_access,
+	.convert_ctx_access	= bpf_net_convert_ctx_access,
 };
 
 static const struct bpf_verifier_ops tc_cls_act_ops = {
-	.get_func_proto = tc_cls_act_func_proto,
-	.is_valid_access = tc_cls_act_is_valid_access,
-	.convert_ctx_access = bpf_net_convert_ctx_access,
+	.get_func_proto		= tc_cls_act_func_proto,
+	.is_valid_access	= tc_cls_act_is_valid_access,
+	.convert_ctx_access	= bpf_net_convert_ctx_access,
 };
 
 static struct bpf_prog_type_list sk_filter_type __read_mostly = {
-	.ops = &sk_filter_ops,
-	.type = BPF_PROG_TYPE_SOCKET_FILTER,
+	.ops	= &sk_filter_ops,
+	.type	= BPF_PROG_TYPE_SOCKET_FILTER,
 };
 
 static struct bpf_prog_type_list sched_cls_type __read_mostly = {
-	.ops = &tc_cls_act_ops,
-	.type = BPF_PROG_TYPE_SCHED_CLS,
+	.ops	= &tc_cls_act_ops,
+	.type	= BPF_PROG_TYPE_SCHED_CLS,
 };
 
 static struct bpf_prog_type_list sched_act_type __read_mostly = {
-	.ops = &tc_cls_act_ops,
-	.type = BPF_PROG_TYPE_SCHED_ACT,
+	.ops	= &tc_cls_act_ops,
+	.type	= BPF_PROG_TYPE_SCHED_ACT,
 };
 
 static int __init register_sk_filter_ops(void)

net/core/sysctl_net_core.c

@@ -294,6 +294,15 @@ static struct ctl_table net_core_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec
 	},
+# ifdef CONFIG_HAVE_EBPF_JIT
+	{
+		.procname	= "bpf_jit_harden",
+		.data		= &bpf_jit_harden,
+		.maxlen		= sizeof(int),
+		.mode		= 0600,
+		.proc_handler	= proc_dointvec,
+	},
+# endif
 #endif
 	{
 		.procname	= "netdev_tstamp_prequeue",