From: Borislav Petkov <b...@suse.de>
Date: Wed, 10 Jan 2018 12:14:07 +0100
We check only the first byte whether it is a NOP but if David Woodhouse
wants to do some crazy experiments with slapping NOPs in front of the
payload and having the actual instructions after it, this "optimized"
test breaks. :-)
Make sure we scan all bytes before we decide to optimize the NOPs in
there.
Reported-by: David Woodhouse <dw...@infradead.org>
Signed-off-by: Borislav Petkov <b...@suse.de>
Cc: x...@kernel.org
---
arch/x86/kernel/alternative.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 3344d3382e91..78932b283915 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -344,9 +344,11 @@ recompute_jump(struct alt_instr *a, u8 *orig_insn, u8
*repl_insn, u8 *insnbuf)
static void __init_or_module noinline optimize_nops(struct alt_instr *a, u8
*instr)
{
unsigned long flags;
+ int i;
- if (instr[0] != 0x90)
- return;
+ for (i = 0; i < a->padlen; i++)
+ if (instr[i] != 0x90)
+ return;
local_irq_save(flags);
add_nops(instr + (a->instrlen - a->padlen), a->padlen);
--
2.13.0
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
