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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 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: qpk48yn8b15p339fu59zy4hpzm9iti59 X-Rspamd-Queue-Id: 9DEB420004 X-Rspamd-Server: rspam01 X-Rspam-User: X-HE-Tag: 1783509617-295597 X-HE-Meta: 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 2bUfN0zM 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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