From 656f57bdf30b41356f47c132e40577eedfa0253a Mon Sep 17 00:00:00 2001 From: James Morse Date: Wed, 20 Apr 2022 11:53:35 +0000 Subject: [PATCH] arm64: entry: Allow tramp_alias to access symbols after the 4K boundary stable inclusion from stable-v4.19.236 commit ebcdd80d0016c7445e8395cec99b9ce266a26001 category: bugfix bugzilla: 186460, https://gitee.com/src-openeuler/kernel/issues/I53MHA CVE: CVE-2022-23960 -------------------------------- commit 6c5bf79b69f911560fbf82214c0971af6e58e682 upstream. Systems using kpti enter and exit the kernel through a trampoline mapping that is always mapped, even when the kernel is not. tramp_valias is a macro to find the address of a symbol in the trampoline mapping. Adding extra sets of vectors will expand the size of the entry.tramp.text section to beyond 4K. tramp_valias will be unable to generate addresses for symbols beyond 4K as it uses the 12 bit immediate of the add instruction. As there are now two registers available when tramp_alias is called, use the extra register to avoid the 4K limit of the 12 bit immediate. Reviewed-by: Russell King (Oracle) Reviewed-by: Catalin Marinas Signed-off-by: James Morse Signed-off-by: Greg Kroah-Hartman Signed-off-by: Chen Jiahao Reviewed-by: Hanjun Guo Reviewed-by: Liao Chang Signed-off-by: Yongqiang Liu --- arch/arm64/kernel/entry.S | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 8de799e92970..15e117d7e290 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -135,9 +135,12 @@ .org .Lventry_start\@ + 128 // Did we overflow the ventry slot? .endm - .macro tramp_alias, dst, sym + .macro tramp_alias, dst, sym, tmp mov_q \dst, TRAMP_VALIAS - add \dst, \dst, #(\sym - .entry.tramp.text) + adr_l \tmp, \sym + add \dst, \dst, \tmp + adr_l \tmp, .entry.tramp.text + sub \dst, \dst, \tmp .endm // This macro corrupts x0-x3. It is the caller's duty @@ -379,10 +382,10 @@ alternative_else_nop_endif #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 bne 4f msr far_el1, x29 - tramp_alias x30, tramp_exit_native + tramp_alias x30, tramp_exit_native, x29 br x30 4: - tramp_alias x30, tramp_exit_compat + tramp_alias x30, tramp_exit_compat, x29 br x30 #endif .else @@ -1365,7 +1368,7 @@ alternative_if_not ARM64_UNMAP_KERNEL_AT_EL0 alternative_else_nop_endif #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 - tramp_alias dst=x5, sym=__sdei_asm_exit_trampoline + tramp_alias dst=x5, sym=__sdei_asm_exit_trampoline, tmp=x3 br x5 #endif ENDPROC(__sdei_asm_handler) -- GitLab