From: Jaeyeon Lee <jaeyeon.lee.dev@gmail.com>
To: akpm@linux-foundation.org, hughd@google.com
Cc: baolin.wang@linux.alibaba.com, elver@google.com,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Jaeyeon Lee <jaeyeon.lee.dev@gmail.com>,
syzbot+dfb578404df369f6599b@syzkaller.appspotmail.com
Subject: [PATCH] mm/shmem: annotate benign data-race in shmem_getattr()
Date: Wed, 8 Jul 2026 13:19:41 +0200 [thread overview]
Message-ID: <20260708111941.35460-1-jaeyeon.lee.dev@gmail.com> (raw)
shmem_getattr() reads info->alloced, info->swapped and
i_mapping->nrpages without info->lock to decide whether
shmem_recalc_inode() should be called. shmem_recalc_inode()
recomputes these under info->lock, so a stale read here only
affects whether shmem_recalc_inode() runs.
Annotate data_race() to silence KCSAN.
Reported-by: syzbot+dfb578404df369f6599b@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=dfb578404df369f6599b
Signed-off-by: Jaeyeon Lee <jaeyeon.lee.dev@gmail.com>
---
mm/shmem.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index 0ea74fa84f25..3fb6dbbfa20b 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1287,7 +1287,8 @@ static int shmem_getattr(struct mnt_idmap *idmap,
struct inode *inode = path->dentry->d_inode;
struct shmem_inode_info *info = SHMEM_I(inode);
- if (info->alloced - info->swapped != inode->i_mapping->nrpages)
+ /* Fast-path hint; recalc under info->lock corrects any stale read. */
+ if (data_race(info->alloced - info->swapped != inode->i_mapping->nrpages))
shmem_recalc_inode(inode, 0, 0);
if (info->fsflags & FS_APPEND_FL)
--
2.43.0
reply other threads:[~2026-07-08 11:20 UTC|newest]
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