From 7cf8f44a5a1c0cb10a594996797e5a988cf0589d Mon Sep 17 00:00:00 2001
From: Alexander Potapenko <glider@google.com>
Date: Thu, 15 Sep 2022 17:04:12 +0200
Subject: x86: fs: kmsan: disable CONFIG_DCACHE_WORD_ACCESS

dentry_string_cmp() calls read_word_at_a_time(), which might read
uninitialized bytes to optimize string comparisons.  Disabling
CONFIG_DCACHE_WORD_ACCESS should prohibit this optimization, as well as
(probably) similar ones.

Link: https://lkml.kernel.org/r/20220915150417.722975-39-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Suggested-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Marco Elver <elver@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 arch/x86/Kconfig | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

(limited to 'arch/x86')

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index eb158eb8a985..edf7f12935d7 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -129,7 +129,9 @@ config X86
 	select CLKEVT_I8253
 	select CLOCKSOURCE_VALIDATE_LAST_CYCLE
 	select CLOCKSOURCE_WATCHDOG
-	select DCACHE_WORD_ACCESS
+	# Word-size accesses may read uninitialized data past the trailing \0
+	# in strings and cause false KMSAN reports.
+	select DCACHE_WORD_ACCESS		if !KMSAN
 	select DYNAMIC_SIGFRAME
 	select EDAC_ATOMIC_SCRUB
 	select EDAC_SUPPORT
-- 
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