diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2022-08-19 13:01:35 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-09-15 12:04:56 +0200 |
| commit | 4e8d7039cf521bbf483fd814b67ec8379c4fc3f9 (patch) | |
| tree | 4371f60d58c80ab1b1db3e2d1c86414019c43588 | |
| parent | 64f9755b408b09feda3dd979a8078c99bd285e42 (diff) | |
x86/nospec: Fix i386 RSB stuffing
commit 332924973725e8cdcc783c175f68cf7e162cb9e5 upstream.
Turns out that i386 doesn't unconditionally have LFENCE, as such the
loop in __FILL_RETURN_BUFFER isn't actually speculation safe on such
chips.
Fixes: ba6e31af2be9 ("x86/speculation: Add LFENCE to RSB fill sequence")
Reported-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/Yv9tj9vbQ9nNlXoY@worktop.programming.kicks-ass.net
[bwh: Backported to 4.19/5.4:
- __FILL_RETURN_BUFFER takes an sp parameter
- Open-code __FILL_RETURN_SLOT]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/x86/include/asm/nospec-branch.h | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index 1e5df3ccdd5c..a1ee1a760c3e 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -44,6 +44,7 @@ * the optimal version — two calls, each with their own speculation * trap should their return address end up getting used, in a loop. */ +#ifdef CONFIG_X86_64 #define __FILL_RETURN_BUFFER(reg, nr, sp) \ mov $(nr/2), reg; \ 771: \ @@ -64,6 +65,19 @@ add $(BITS_PER_LONG/8) * nr, sp; \ /* barrier for jnz misprediction */ \ lfence; +#else +/* + * i386 doesn't unconditionally have LFENCE, as such it can't + * do a loop. + */ +#define __FILL_RETURN_BUFFER(reg, nr, sp) \ + .rept nr; \ + call 772f; \ + int3; \ +772:; \ + .endr; \ + add $(BITS_PER_LONG/8) * nr, sp; +#endif #define __ISSUE_UNBALANCED_RET_GUARD(sp) \ call 881f; \ |