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[128.130.237.117]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-493e0faed92sm122363945e9.9.2026.07.08.04.20.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Jul 2026 04:20:15 -0700 (PDT) From: Jaeyeon Lee 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 , 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 Message-ID: <20260708111941.35460-1-jaeyeon.lee.dev@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- 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