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Sat, 04 May 2024 16:05:15 +0800 (CST) From: libaokun@huaweicloud.com To: linux-ext4@vger.kernel.org Cc: tytso@mit.edu, adilger.kernel@dilger.ca, jack@suse.cz, ritesh.list@gmail.com, linux-kernel@vger.kernel.org, yi.zhang@huawei.com, yangerkun@huawei.com, libaokun@huaweicloud.com, Baokun Li , syzbot+dd43bd0f7474512edc47@syzkaller.appspotmail.com, stable@kernel.org Subject: [PATCH 1/2] ext4: fix mb_cache_entry's e_refcnt leak in ext4_xattr_block_cache_find() Date: Sat, 4 May 2024 15:55:25 +0800 Message-Id: <20240504075526.2254349-2-libaokun@huaweicloud.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240504075526.2254349-1-libaokun@huaweicloud.com> References: <20240504075526.2254349-1-libaokun@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CM-TRANSID: cCh0CgCXaBE57DVmKbDhLg--.23467S5 X-Coremail-Antispam: 1UD129KBjvJXoWxJrWxXw4DWr45WrWkZrWUJwb_yoW8ZrW8p3 s7KryIyrWFq34UAayfKr1Iqw18ua1kGF47J3yxKr1UZa47Xwn3Ka4jqrn8XFyqgrWv9wn0 yF1DK343Aw1rG3DanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUPl14x267AKxVW5JVWrJwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWUuVWrJwAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_Jr4l82xGYIkIc2 x26xkF7I0E14v26r1I6r4UM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2z4x0 Y4vE2Ix0cI8IcVAFwI0_Xr0_Ar1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Cr0_Gr1UM2 8EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I0E14v26rxl6s0DM2AI xVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMcIj6xIIjxv20x vE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xv r2IYc2Ij64vIr41lF7I21c0EjII2zVCS5cI20VAGYxC7M4IIrI8v6xkF7I0E8cxan2IY04 v7M4kE6xkIj40Ew7xC0wCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC2 0s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI 0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv2 0xvEc7CjxVAFwI0_Gr0_Cr1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2js IE14v26r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZF pf9x0JUhTmDUUUUU= X-CM-SenderInfo: 5olet0hnxqqx5xdzvxpfor3voofrz/ From: Baokun Li Syzbot reports a warning as follows: ============================================ WARNING: CPU: 0 PID: 5075 at fs/mbcache.c:419 mb_cache_destroy+0x224/0x290 Modules linked in: CPU: 0 PID: 5075 Comm: syz-executor199 Not tainted 6.9.0-rc6-gb947cc5bf6d7 RIP: 0010:mb_cache_destroy+0x224/0x290 fs/mbcache.c:419 Call Trace: ext4_put_super+0x6d4/0xcd0 fs/ext4/super.c:1375 generic_shutdown_super+0x136/0x2d0 fs/super.c:641 kill_block_super+0x44/0x90 fs/super.c:1675 ext4_kill_sb+0x68/0xa0 fs/ext4/super.c:7327 [...] ============================================ This is because when finding an entry in ext4_xattr_block_cache_find(), if ext4_sb_bread() returns -ENOMEM, the ce's e_refcnt, which has already grown in the __entry_find(), won't be put away, and eventually trigger the above issue in mb_cache_destroy() due to reference count leakage. So call mb_cache_entry_put() on the -ENOMEM error branch as a quick fix. Reported-by: syzbot+dd43bd0f7474512edc47@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=dd43bd0f7474512edc47 Fixes: fb265c9cb49e ("ext4: add ext4_sb_bread() to disambiguate ENOMEM cases") Cc: stable@kernel.org Signed-off-by: Baokun Li Reviewed-by: Jan Kara --- fs/ext4/xattr.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c index b67a176bfcf9..9fdd13422073 100644 --- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c @@ -3113,8 +3113,10 @@ ext4_xattr_block_cache_find(struct inode *inode, bh = ext4_sb_bread(inode->i_sb, ce->e_value, REQ_PRIO); if (IS_ERR(bh)) { - if (PTR_ERR(bh) == -ENOMEM) + if (PTR_ERR(bh) == -ENOMEM) { + mb_cache_entry_put(ea_block_cache, ce); return NULL; + } bh = NULL; EXT4_ERROR_INODE(inode, "block %lu read error", (unsigned long)ce->e_value);