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authorBorislav Petkov <bp@suse.de>2018-01-10 12:28:16 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-01-17 09:45:28 +0100
commitb50f563f7c1a4dc307ba2d7f3f9b8ef2f98a2aa2 (patch)
tree33bd480667f608a01e97bb877922579c306448b3
parent31431b7b4665cae7bc197980e42a5f3728258688 (diff)
x86/alternatives: Fix optimize_nops() checking
commit 612e8e9350fd19cae6900cf36ea0c6892d1a0dca upstream. The alternatives code checks only the first byte whether it is a NOP, but with NOPs in front of the payload and having actual instructions after it breaks the "optimized' test. Make sure to scan all bytes before deciding to optimize the NOPs in there. Reported-by: David Woodhouse <dwmw2@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Jiri Kosina <jikos@kernel.org> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Andrew Lutomirski <luto@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org> Cc: Paul Turner <pjt@google.com> Link: https://lkml.kernel.org/r/20180110112815.mgciyf5acwacphkq@pd.tnic Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/x86/kernel/alternative.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 3344d3382e91..e0b97e4d1db5 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -344,9 +344,12 @@ done:
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);