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Subject[PATCH 4.4 159/241] x86/ia32: Fix ia32_restore_sigcontext() AC leak
Date
[ 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 0552884da18db..a7b9acd709dbc 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -60,9 +60,8 @@
} 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); \
}
@@ -71,6 +70,7 @@ 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;

@@ -78,16 +78,10 @@ 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);
@@ -105,6 +99,17 @@ 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


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