Messages in this thread Patch in this message | | | Date | Wed, 10 Jan 2018 09:33:55 -0800 | From | tip-bot for Borislav Petkov <> | Subject | [tip:x86/pti] x86/alternatives: Fix optimize_nops() checking |
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Commit-ID: d1cb4348f683d132ef2d468d4e9ad421486163f9 Gitweb: https://git.kernel.org/tip/d1cb4348f683d132ef2d468d4e9ad421486163f9 Author: Borislav Petkov <bp@suse.de> AuthorDate: Wed, 10 Jan 2018 12:28:16 +0100 Committer: Thomas Gleixner <tglx@linutronix.de> CommitDate: Wed, 10 Jan 2018 18:28:21 +0100
x86/alternatives: Fix optimize_nops() checking
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
--- arch/x86/kernel/alternative.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 3344d33..e0b97e4 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);
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