From: Borislav Petkov <bp@alien8.de>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Andi Kleen <andi@firstfloor.org>,
Thomas Gleixner <tglx@linutronix.de>,
the arch/x86 maintainers <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Paul Turner <pjt@google.com>, Andrew Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Tom Lendacky <thomas.lendacky@amd.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
Greg Kroah-Hartman <gregkh@linux-foundation.org>,
Dave Hansen <dave.hansen@intel.com>,
Jiri Kosina <jikos@kernel.org>, Andi Kleen <ak@linux.intel.com>
Subject: [PATCH] x86/alternatives: Fix optimize_nops() checking
Date: Wed, 10 Jan 2018 12:28:16 +0100 [thread overview]
Message-ID: <20180110112815.mgciyf5acwacphkq@pd.tnic> (raw)
In-Reply-To: <1515578735.22302.91.camel@infradead.org>
From: Borislav Petkov <bp@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 <dwmw2@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: x86@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.
next prev parent reply other threads:[~2018-01-10 11:28 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-10 0:31 [PATCH] x86/retpoline: Fix NOSPEC_JMP for tip Andi Kleen
2018-01-10 0:39 ` Thomas Gleixner
2018-01-10 0:39 ` Linus Torvalds
2018-01-10 0:40 ` Thomas Gleixner
2018-01-10 0:45 ` Tom Lendacky
2018-01-10 0:50 ` Thomas Gleixner
2018-01-10 1:30 ` Andi Kleen
2018-01-10 1:36 ` Andi Kleen
2018-01-10 1:50 ` Thomas Gleixner
2018-01-10 1:57 ` Andi Kleen
2018-01-10 9:05 ` David Woodhouse
2018-01-10 0:51 ` Andi Kleen
2018-01-10 1:05 ` Thomas Gleixner
2018-01-10 7:15 ` David Woodhouse
2018-01-10 10:05 ` David Woodhouse
2018-01-10 11:28 ` Borislav Petkov [this message]
2018-01-10 11:36 ` [PATCH] x86/alternatives: Fix optimize_nops() checking David Woodhouse
2018-01-10 11:45 ` Borislav Petkov
2018-01-10 11:49 ` David Woodhouse
2018-01-10 11:57 ` Borislav Petkov
2018-01-10 11:58 ` David Woodhouse
2018-01-10 17:33 ` [tip:x86/pti] " tip-bot for Borislav Petkov
2018-01-10 18:12 ` tip-bot for Borislav Petkov
2018-01-10 18:39 ` tip-bot for Borislav Petkov
2018-01-10 19:38 ` [PATCH] " Linus Torvalds
2018-01-10 19:55 ` Thomas Gleixner
2018-01-10 20:15 ` Josh Poimboeuf
2018-01-10 20:19 ` David Woodhouse
2018-01-10 20:26 ` Linus Torvalds
2018-01-10 20:33 ` Peter Zijlstra
2018-01-10 20:36 ` David Woodhouse
2018-01-10 20:49 ` Linus Torvalds
2018-01-10 20:55 ` Borislav Petkov
2018-01-10 21:05 ` Linus Torvalds
2018-01-10 21:08 ` David Woodhouse
2018-01-10 21:11 ` Linus Torvalds
2018-01-10 21:16 ` Josh Poimboeuf
2018-01-10 21:17 ` Linus Torvalds
2018-01-10 21:27 ` Josh Poimboeuf
2018-01-10 21:10 ` Borislav Petkov
2018-01-10 20:55 ` Josh Poimboeuf
2018-01-10 20:05 ` Borislav Petkov
2018-01-10 20:20 ` Linus Torvalds
2018-01-10 20:50 ` Borislav Petkov
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