[merged mm-stable] mm-slub-disable-kmsan-when-checking-the-padding-bytes.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
Subject: mm: slub: disable KMSAN when checking the padding bytes
has been removed from the -mm tree. Its filename was
mm-slub-disable-kmsan-when-checking-the-padding-bytes.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Ilya Leoshkevich <i...@linux.ibm.com>
Subject: mm: slub: disable KMSAN when checking the padding bytes
Date: Fri, 21 Jun 2024 13:35:02 +0200

Even though the KMSAN warnings generated by memchr_inv() are suppressed by
metadata_access_enable(), its return value may still be poisoned.

The reason is that the last iteration of memchr_inv() returns `*start !=
value ? start : NULL`, where *start is poisoned. Because of this,
somewhat counterintuitively, the shadow value computed by
visitSelectInst() is equal to `(uintptr_t)start`.

One possibility to fix this, since the intention behind guarding
memchr_inv() behind metadata_access_enable() is to touch poisoned metadata
without triggering KMSAN, is to unpoison its return value. However, this
approach is too fragile. So simply disable the KMSAN checks in the
respective functions.

Link: https://lkml.kernel.org/r/20240621113706...@linux.ibm.com
Signed-off-by: Ilya Leoshkevich <i...@linux.ibm.com>
Reviewed-by: Alexander Potapenko <gli...@google.com>
Cc: Alexander Gordeev <agor...@linux.ibm.com>
Cc: Christian Borntraeger <bornt...@linux.ibm.com>
Cc: Christoph Lameter <c...@linux.com>
Cc: David Rientjes <rien...@google.com>
Cc: Dmitry Vyukov <dvy...@google.com>
Cc: Heiko Carstens <h...@linux.ibm.com>
Cc: Hyeonggon Yoo <42.h...@gmail.com>
Cc: Joonsoo Kim <iamjoon...@lge.com>
Cc: <kasa...@googlegroups.com>
Cc: Marco Elver <el...@google.com>
Cc: Mark Rutland <mark.r...@arm.com>
Cc: Masami Hiramatsu (Google) <mhir...@kernel.org>
Cc: Pekka Enberg <pen...@kernel.org>
Cc: Roman Gushchin <roman.g...@linux.dev>
Cc: Steven Rostedt (Google) <ros...@goodmis.org>
Cc: Sven Schnelle <sv...@linux.ibm.com>
Cc: Vasily Gorbik <g...@linux.ibm.com>
Cc: Vlastimil Babka <vba...@suse.cz>
Signed-off-by: Andrew Morton <ak...@linux-foundation.org>
---

mm/slub.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)

--- a/mm/slub.c~mm-slub-disable-kmsan-when-checking-the-padding-bytes
+++ a/mm/slub.c
@@ -1176,9 +1176,16 @@ static void restore_bytes(struct kmem_ca
memset(from, data, to - from);
}

-static int check_bytes_and_report(struct kmem_cache *s, struct slab *slab,
- u8 *object, char *what,
- u8 *start, unsigned int value, unsigned int bytes)
+#ifdef CONFIG_KMSAN
+#define pad_check_attributes noinline __no_kmsan_checks
+#else
+#define pad_check_attributes
+#endif
+
+static pad_check_attributes int
+check_bytes_and_report(struct kmem_cache *s, struct slab *slab,
+ u8 *object, char *what,
+ u8 *start, unsigned int value, unsigned int bytes)
{
u8 *fault;
u8 *end;
@@ -1270,7 +1277,8 @@ static int check_pad_bytes(struct kmem_c
}

/* Check the pad bytes at the end of a slab page */
-static void slab_pad_check(struct kmem_cache *s, struct slab *slab)
+static pad_check_attributes void
+slab_pad_check(struct kmem_cache *s, struct slab *slab)
{
u8 *start;
u8 *fault;
_

Patches currently in -mm which might be from i...@linux.ibm.com are