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Commit | Line | Data |
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6063b8b5 GKH |
1 | From 612e8e9350fd19cae6900cf36ea0c6892d1a0dca Mon Sep 17 00:00:00 2001 |
2 | From: Borislav Petkov <bp@suse.de> | |
3 | Date: Wed, 10 Jan 2018 12:28:16 +0100 | |
4 | Subject: x86/alternatives: Fix optimize_nops() checking | |
5 | ||
6 | From: Borislav Petkov <bp@suse.de> | |
7 | ||
8 | commit 612e8e9350fd19cae6900cf36ea0c6892d1a0dca upstream. | |
9 | ||
10 | The alternatives code checks only the first byte whether it is a NOP, but | |
11 | with NOPs in front of the payload and having actual instructions after it | |
12 | breaks the "optimized' test. | |
13 | ||
14 | Make sure to scan all bytes before deciding to optimize the NOPs in there. | |
15 | ||
16 | Reported-by: David Woodhouse <dwmw2@infradead.org> | |
17 | Signed-off-by: Borislav Petkov <bp@suse.de> | |
18 | Signed-off-by: Thomas Gleixner <tglx@linutronix.de> | |
19 | Cc: Tom Lendacky <thomas.lendacky@amd.com> | |
20 | Cc: Andi Kleen <ak@linux.intel.com> | |
21 | Cc: Tim Chen <tim.c.chen@linux.intel.com> | |
22 | Cc: Peter Zijlstra <peterz@infradead.org> | |
23 | Cc: Jiri Kosina <jikos@kernel.org> | |
24 | Cc: Dave Hansen <dave.hansen@intel.com> | |
25 | Cc: Andi Kleen <andi@firstfloor.org> | |
26 | Cc: Andrew Lutomirski <luto@kernel.org> | |
27 | Cc: Linus Torvalds <torvalds@linux-foundation.org> | |
28 | Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org> | |
29 | Cc: Paul Turner <pjt@google.com> | |
30 | Link: https://lkml.kernel.org/r/20180110112815.mgciyf5acwacphkq@pd.tnic | |
31 | Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> | |
32 | ||
33 | --- | |
34 | arch/x86/kernel/alternative.c | 7 +++++-- | |
35 | 1 file changed, 5 insertions(+), 2 deletions(-) | |
36 | ||
37 | --- a/arch/x86/kernel/alternative.c | |
38 | +++ b/arch/x86/kernel/alternative.c | |
39 | @@ -344,9 +344,12 @@ done: | |
40 | static void __init_or_module noinline optimize_nops(struct alt_instr *a, u8 *instr) | |
41 | { | |
42 | unsigned long flags; | |
43 | + int i; | |
44 | ||
45 | - if (instr[0] != 0x90) | |
46 | - return; | |
47 | + for (i = 0; i < a->padlen; i++) { | |
48 | + if (instr[i] != 0x90) | |
49 | + return; | |
50 | + } | |
51 | ||
52 | local_irq_save(flags); | |
53 | add_nops(instr + (a->instrlen - a->padlen), a->padlen); |