From: Peter Zijlstra peterz@infradead.org
stable inclusion from stable-v5.10.133 commit 28ca351296742a9e7506a548acaf7ea3bc9feef0 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5PTAS CVE: CVE-2022-29900,CVE-2022-23816,CVE-2022-29901
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
--------------------------------
commit 119251855f9adf9421cb5eb409933092141ab2c7 upstream.
Due to:
c9c324dc22aa ("objtool: Support stack layout changes in alternatives")
it is now possible to simplify the retpolines.
Currently our retpolines consist of 2 symbols:
- __x86_indirect_thunk_\reg: the compiler target - __x86_retpoline_\reg: the actual retpoline.
Both are consecutive in code and aligned such that for any one register they both live in the same cacheline:
0000000000000000 <__x86_indirect_thunk_rax>: 0: ff e0 jmpq *%rax 2: 90 nop 3: 90 nop 4: 90 nop
0000000000000005 <__x86_retpoline_rax>: 5: e8 07 00 00 00 callq 11 <__x86_retpoline_rax+0xc> a: f3 90 pause c: 0f ae e8 lfence f: eb f9 jmp a <__x86_retpoline_rax+0x5> 11: 48 89 04 24 mov %rax,(%rsp) 15: c3 retq 16: 66 2e 0f 1f 84 00 00 00 00 00 nopw %cs:0x0(%rax,%rax,1)
The thunk is an alternative_2, where one option is a JMP to the retpoline. This was done so that objtool didn't need to deal with alternatives with stack ops. But that problem has been solved, so now it is possible to fold the entire retpoline into the alternative to simplify and consolidate unused bytes:
0000000000000000 <__x86_indirect_thunk_rax>: 0: ff e0 jmpq *%rax 2: 90 nop 3: 90 nop 4: 90 nop 5: 90 nop 6: 90 nop 7: 90 nop 8: 90 nop 9: 90 nop a: 90 nop b: 90 nop c: 90 nop d: 90 nop e: 90 nop f: 90 nop 10: 90 nop 11: 66 66 2e 0f 1f 84 00 00 00 00 00 data16 nopw %cs:0x0(%rax,%rax,1) 1c: 0f 1f 40 00 nopl 0x0(%rax)
Notice that since the longest alternative sequence is now:
0: e8 07 00 00 00 callq c <.altinstr_replacement+0xc> 5: f3 90 pause 7: 0f ae e8 lfence a: eb f9 jmp 5 <.altinstr_replacement+0x5> c: 48 89 04 24 mov %rax,(%rsp) 10: c3 retq
17 bytes, we have 15 bytes NOP at the end of our 32 byte slot. (IOW, if we can shrink the retpoline by 1 byte we can pack it more densely).
[ bp: Massage commit message. ]
Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Borislav Petkov bp@suse.de Signed-off-by: Ingo Molnar mingo@kernel.org Link: https://lkml.kernel.org/r/20210326151259.506071949@infradead.org [bwh: Backported to 5.10: - Use X86_FEATRURE_RETPOLINE_LFENCE flag instead of X86_FEATURE_RETPOLINE_AMD, since the later renaming of this flag has already been applied - Adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Lin Yujun linyujun809@huawei.com Reviewed-by: Zhang Jianhua chris.zjh@huawei.com --- arch/x86/include/asm/asm-prototypes.h | 7 ------ arch/x86/include/asm/nospec-branch.h | 6 ++--- arch/x86/lib/retpoline.S | 34 +++++++++++++-------------- tools/objtool/check.c | 3 +-- 4 files changed, 21 insertions(+), 29 deletions(-)
diff --git a/arch/x86/include/asm/asm-prototypes.h b/arch/x86/include/asm/asm-prototypes.h index 51e2bf27cc9b..0545b07895a5 100644 --- a/arch/x86/include/asm/asm-prototypes.h +++ b/arch/x86/include/asm/asm-prototypes.h @@ -22,15 +22,8 @@ extern void cmpxchg8b_emu(void); #define DECL_INDIRECT_THUNK(reg) \ extern asmlinkage void __x86_indirect_thunk_ ## reg (void);
-#define DECL_RETPOLINE(reg) \ - extern asmlinkage void __x86_retpoline_ ## reg (void); - #undef GEN #define GEN(reg) DECL_INDIRECT_THUNK(reg) #include <asm/GEN-for-each-reg.h>
-#undef GEN -#define GEN(reg) DECL_RETPOLINE(reg) -#include <asm/GEN-for-each-reg.h> - #endif /* CONFIG_RETPOLINE */ diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index c5820916cd4f..838c15e1b775 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -80,7 +80,7 @@ .macro JMP_NOSPEC reg:req #ifdef CONFIG_RETPOLINE ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \ - __stringify(jmp __x86_retpoline_\reg), X86_FEATURE_RETPOLINE, \ + __stringify(jmp __x86_indirect_thunk_\reg), X86_FEATURE_RETPOLINE, \ __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), X86_FEATURE_RETPOLINE_LFENCE #else jmp *%\reg @@ -90,7 +90,7 @@ .macro CALL_NOSPEC reg:req #ifdef CONFIG_RETPOLINE ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; call *%\reg), \ - __stringify(call __x86_retpoline_\reg), X86_FEATURE_RETPOLINE, \ + __stringify(call __x86_indirect_thunk_\reg), X86_FEATURE_RETPOLINE, \ __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; call *%\reg), X86_FEATURE_RETPOLINE_LFENCE #else call *%\reg @@ -128,7 +128,7 @@ ALTERNATIVE_2( \ ANNOTATE_RETPOLINE_SAFE \ "call *%[thunk_target]\n", \ - "call __x86_retpoline_%V[thunk_target]\n", \ + "call __x86_indirect_thunk_%V[thunk_target]\n", \ X86_FEATURE_RETPOLINE, \ "lfence;\n" \ ANNOTATE_RETPOLINE_SAFE \ diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S index 6bb74b5c238c..b22075d6e38d 100644 --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -10,27 +10,31 @@ #include <asm/unwind_hints.h> #include <asm/frame.h>
-.macro THUNK reg - .section .text.__x86.indirect_thunk - - .align 32 -SYM_FUNC_START(__x86_indirect_thunk_\reg) - JMP_NOSPEC \reg -SYM_FUNC_END(__x86_indirect_thunk_\reg) - -SYM_FUNC_START_NOALIGN(__x86_retpoline_\reg) +.macro RETPOLINE reg ANNOTATE_INTRA_FUNCTION_CALL - call .Ldo_rop_@ + call .Ldo_rop_@ .Lspec_trap_@: UNWIND_HINT_EMPTY pause lfence - jmp .Lspec_trap_@ + jmp .Lspec_trap_@ .Ldo_rop_@: - mov %\reg, (%_ASM_SP) + mov %\reg, (%_ASM_SP) UNWIND_HINT_FUNC ret -SYM_FUNC_END(__x86_retpoline_\reg) +.endm + +.macro THUNK reg + .section .text.__x86.indirect_thunk + + .align 32 +SYM_FUNC_START(__x86_indirect_thunk_\reg) + + ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \ + __stringify(RETPOLINE \reg), X86_FEATURE_RETPOLINE, \ + __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), X86_FEATURE_RETPOLINE_LFENCE + +SYM_FUNC_END(__x86_indirect_thunk_\reg)
.endm
@@ -48,7 +52,6 @@ SYM_FUNC_END(__x86_retpoline_\reg)
#define __EXPORT_THUNK(sym) _ASM_NOKPROBE(sym); EXPORT_SYMBOL(sym) #define EXPORT_THUNK(reg) __EXPORT_THUNK(__x86_indirect_thunk_ ## reg) -#define EXPORT_RETPOLINE(reg) __EXPORT_THUNK(__x86_retpoline_ ## reg)
#undef GEN #define GEN(reg) THUNK reg @@ -58,6 +61,3 @@ SYM_FUNC_END(__x86_retpoline_\reg) #define GEN(reg) EXPORT_THUNK(reg) #include <asm/GEN-for-each-reg.h>
-#undef GEN -#define GEN(reg) EXPORT_RETPOLINE(reg) -#include <asm/GEN-for-each-reg.h> diff --git a/tools/objtool/check.c b/tools/objtool/check.c index ed5e4b04f508..334781ee60f1 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -800,8 +800,7 @@ static int add_jump_destinations(struct objtool_file *file) } else if (reloc->sym->type == STT_SECTION) { dest_sec = reloc->sym->sec; dest_off = arch_dest_reloc_offset(reloc->addend); - } else if (!strncmp(reloc->sym->name, "__x86_indirect_thunk_", 21) || - !strncmp(reloc->sym->name, "__x86_retpoline_", 16)) { + } else if (!strncmp(reloc->sym->name, "__x86_indirect_thunk_", 21)) { /* * Retpoline jumps are really dynamic jumps in * disguise, so convert them accordingly.