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mm/shmem: annotate benign data-race in shmem_getattr()

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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.

Link: https://lore.kernel.org/20260708111941.35460-1-jaeyeon.lee.dev@gmail.com
Signed-off-by: Jaeyeon Lee <jaeyeon.lee.dev@gmail.com>
Reported-by: syzbot+dfb578404df369f6599b@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=dfb578404df369f6599b
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Jaeyeon Lee
2026-07-08 13:19:41 +02:00
committed by Andrew Morton
parent 3fe0620fae
commit 889d3783ae
1 changed files with 2 additions and 1 deletions
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3
mm/shmem.c
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@@ -1297,7 +1297,8 @@ 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)