| From 171fd9d373d632a760ad42234a8d4c3ceb52b44f Mon Sep 17 00:00:00 2001 |
| From: Peter Zijlstra <peterz@infradead.org> |
| Date: Mon, 25 Feb 2019 12:56:35 +0100 |
| Subject: x86/ia32: Fix ia32_restore_sigcontext() AC leak |
| |
| [ Upstream commit 67a0514afdbb8b2fc70b771b8c77661a9cb9d3a9 ] |
| |
| Objtool spotted that we call native_load_gs_index() with AC set. |
| Re-arrange the code to avoid that. |
| |
| Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> |
| Cc: Borislav Petkov <bp@alien8.de> |
| Cc: Josh Poimboeuf <jpoimboe@redhat.com> |
| Cc: Linus Torvalds <torvalds@linux-foundation.org> |
| Cc: Peter Zijlstra <peterz@infradead.org> |
| Cc: Thomas Gleixner <tglx@linutronix.de> |
| Signed-off-by: Ingo Molnar <mingo@kernel.org> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| arch/x86/ia32/ia32_signal.c | 29 +++++++++++++++++------------ |
| 1 file changed, 17 insertions(+), 12 deletions(-) |
| |
| diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c |
| index 321fe5f5d0e96..4d5fcd47ab75a 100644 |
| --- a/arch/x86/ia32/ia32_signal.c |
| +++ b/arch/x86/ia32/ia32_signal.c |
| @@ -61,9 +61,8 @@ |
| } while (0) |
| |
| #define RELOAD_SEG(seg) { \ |
| - unsigned int pre = GET_SEG(seg); \ |
| + unsigned int pre = (seg) | 3; \ |
| unsigned int cur = get_user_seg(seg); \ |
| - pre |= 3; \ |
| if (pre != cur) \ |
| set_user_seg(seg, pre); \ |
| } |
| @@ -72,6 +71,7 @@ static int ia32_restore_sigcontext(struct pt_regs *regs, |
| struct sigcontext_32 __user *sc) |
| { |
| unsigned int tmpflags, err = 0; |
| + u16 gs, fs, es, ds; |
| void __user *buf; |
| u32 tmp; |
| |
| @@ -79,16 +79,10 @@ static int ia32_restore_sigcontext(struct pt_regs *regs, |
| current->restart_block.fn = do_no_restart_syscall; |
| |
| get_user_try { |
| - /* |
| - * Reload fs and gs if they have changed in the signal |
| - * handler. This does not handle long fs/gs base changes in |
| - * the handler, but does not clobber them at least in the |
| - * normal case. |
| - */ |
| - RELOAD_SEG(gs); |
| - RELOAD_SEG(fs); |
| - RELOAD_SEG(ds); |
| - RELOAD_SEG(es); |
| + gs = GET_SEG(gs); |
| + fs = GET_SEG(fs); |
| + ds = GET_SEG(ds); |
| + es = GET_SEG(es); |
| |
| COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx); |
| COPY(dx); COPY(cx); COPY(ip); COPY(ax); |
| @@ -106,6 +100,17 @@ static int ia32_restore_sigcontext(struct pt_regs *regs, |
| buf = compat_ptr(tmp); |
| } get_user_catch(err); |
| |
| + /* |
| + * Reload fs and gs if they have changed in the signal |
| + * handler. This does not handle long fs/gs base changes in |
| + * the handler, but does not clobber them at least in the |
| + * normal case. |
| + */ |
| + RELOAD_SEG(gs); |
| + RELOAD_SEG(fs); |
| + RELOAD_SEG(ds); |
| + RELOAD_SEG(es); |
| + |
| err |= fpu__restore_sig(buf, 1); |
| |
| force_iret(); |
| -- |
| 2.20.1 |
| |