Messages in this thread Patch in this message | | | Date | Sat, 15 Jan 2022 09:13:24 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86/entry_32: Fix segment exceptions |
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On Fri, Jan 14, 2022 at 03:48:31PM -0800, Andy Lutomirski wrote: > Acked-by: Andy Lutomirski <luto@kernel.org>
I actually did this new version:
--- From: Borislav Petkov <bp@suse.de> Subject: [PATCH] x86/entry_32: Remove GS from the pt_regs offsets and fixup regs
Document how GS (and its stack slot) on 32-bit are used.
Fixes: 9cdbeec40968 ("x86/entry_32: Fix segment exceptions") Signed-off-by: Borislav Petkov <bp@suse.de> --- arch/x86/entry/entry_32.S | 4 +++- arch/x86/include/asm/extable_fixup_types.h | 5 +++-- arch/x86/lib/insn-eval.c | 5 ++++- 3 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index a7ec22b1d06c..addc3966ee20 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -20,7 +20,9 @@ * 1C(%esp) - %ds * 20(%esp) - %es * 24(%esp) - %fs - * 28(%esp) - unused -- was %gs on old stackprotector kernels + * 28(%esp) - unused -- was %gs on old stackprotector kernels. %gs is unused in + * kernel mode in 32-bit and holds the user value. When handling exceptions, the + * C-exception handler address is pushed into the GS-slot on the stack. * 2C(%esp) - orig_eax * 30(%esp) - %eip * 34(%esp) - %cs diff --git a/arch/x86/include/asm/extable_fixup_types.h b/arch/x86/include/asm/extable_fixup_types.h index 503622627400..0aa5f4d3234f 100644 --- a/arch/x86/include/asm/extable_fixup_types.h +++ b/arch/x86/include/asm/extable_fixup_types.h @@ -20,11 +20,12 @@ #define EX_DATA_FLAG(flag) ((flag) << EX_DATA_FLAG_SHIFT) #define EX_DATA_IMM(imm) ((imm) << EX_DATA_IMM_SHIFT) -/* segment regs */ +#ifdef CONFIG_X86_32 +/* segment regs, valid only for 32-bit code, see pt_regoff */ #define EX_REG_DS EX_DATA_REG(8) #define EX_REG_ES EX_DATA_REG(9) #define EX_REG_FS EX_DATA_REG(10) -#define EX_REG_GS EX_DATA_REG(11) +#endif /* flags */ #define EX_FLAG_CLEAR_AX EX_DATA_FLAG(1) diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c index b781d324211b..cfc4d13b7d5b 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -432,7 +432,10 @@ static const int pt_regoff[] = { offsetof(struct pt_regs, ds), offsetof(struct pt_regs, es), offsetof(struct pt_regs, fs), - offsetof(struct pt_regs, gs), + /* + * Can't use that one, see top of entry_32.S + * offsetof(struct pt_regs, gs), + */ #endif }; -- 2.29.2
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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