fs: add sysctl knob for exec_hugetlb

euleros inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4X1VR
CVE: NA

------------
If we have a bug in this feature, users can disable exec_hugetlb
without changing application binaries.
Signed-off-by: NLiu Zixian <liuzixian4@huawei.com>
Reviewed-by: NZhou Kang <zhoukang7@huawei.com>
Reviewed-by: NKefeng Wang <wangkefeng.wang@huawei.com>

fs/binfmt_elf.c

@@ -474,7 +474,7 @@ static unsigned long elf_map(struct file *filep, unsigned long addr,
 		return addr;
 
 #ifdef CONFIG_EXEC_HUGETLB
-	if (eppnt->p_flags & PF_HUGETLB)
+	if (exec_hugetlb && (eppnt->p_flags & PF_HUGETLB))
 		return elf_hugetlb_map(filep, addr, eppnt, prot, type,
 				total_size);
 #endif
@@ -1308,7 +1308,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 		 * bss is allocated in elf_hugetlb_bss,
 		 * so skip vm_brk_flags in set_brk
 		 */
-		if (elf_ppnt->p_flags & PF_HUGETLB)
+		if (exec_hugetlb && (elf_ppnt->p_flags & PF_HUGETLB))
 			elf_bss = elf_brk = ELF_HPAGEALIGN(elf_brk);
 #endif
 	}

fs/exec.c

@@ -74,6 +74,10 @@
 
 #include <trace/events/sched.h>
 
+#ifdef CONFIG_EXEC_HUGETLB
+int exec_hugetlb;
+#endif
+
 static int bprm_creds_from_file(struct linux_binprm *bprm);
 
 int suid_dumpable = 0;

include/linux/elf.h

@@ -99,4 +99,8 @@ static inline int arch_elf_adjust_prot(int prot,
 }
 #endif
 
+#ifdef CONFIG_EXEC_HUGETLB
+extern int exec_hugetlb;
+#endif
+
 #endif /* _LINUX_ELF_H */

kernel/sysctl.c

@@ -3543,6 +3543,17 @@ static struct ctl_table fs_table[] = {
 		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= SYSCTL_ONE,
 	},
+#ifdef CONFIG_EXEC_HUGETLB
+	{
+		.procname	= "exec-use-hugetlb",
+		.data		= &exec_hugetlb,
+		.maxlen		= sizeof(exec_hugetlb),
+		.mode		= 0600,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+#endif
 	{ }
 };