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([240d:1a:c0d:9f00:fc9c:8ee9:e32c:2d9]) by smtp.gmail.com with ESMTPSA id t10-20020a63444a000000b0041c0c9c0072sm15523583pgk.64.2022.10.23.02.57.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 23 Oct 2022 02:57:52 -0700 (PDT) From: Shigeru Yoshida To: jack@suse.com Cc: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, Shigeru Yoshida , syzbot+7902cd7684bc35306224@syzkaller.appspotmail.com Subject: [PATCH] udf: Avoid double brelse() in udf_rename() Date: Sun, 23 Oct 2022 18:57:41 +0900 Message-Id: <20221023095741.271430-1-syoshida@redhat.com> X-Mailer: git-send-email 2.37.3 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" syzbot reported a warning like below [1]: VFS: brelse: Trying to free free buffer WARNING: CPU: 2 PID: 7301 at fs/buffer.c:1145 __brelse+0x67/0xa0 ... Call Trace: invalidate_bh_lru+0x99/0x150 smp_call_function_many_cond+0xe2a/0x10c0 ? generic_remap_file_range_prep+0x50/0x50 ? __brelse+0xa0/0xa0 ? __mutex_lock+0x21c/0x12d0 ? smp_call_on_cpu+0x250/0x250 ? rcu_read_lock_sched_held+0xb/0x60 ? lock_release+0x587/0x810 ? __brelse+0xa0/0xa0 ? generic_remap_file_range_prep+0x50/0x50 on_each_cpu_cond_mask+0x3c/0x80 blkdev_flush_mapping+0x13a/0x2f0 blkdev_put_whole+0xd3/0xf0 blkdev_put+0x222/0x760 deactivate_locked_super+0x96/0x160 deactivate_super+0xda/0x100 cleanup_mnt+0x222/0x3d0 task_work_run+0x149/0x240 ? task_work_cancel+0x30/0x30 do_exit+0xb29/0x2a40 ? reacquire_held_locks+0x4a0/0x4a0 ? do_raw_spin_lock+0x12a/0x2b0 ? mm_update_next_owner+0x7c0/0x7c0 ? rwlock_bug.part.0+0x90/0x90 ? zap_other_threads+0x234/0x2d0 do_group_exit+0xd0/0x2a0 __x64_sys_exit_group+0x3a/0x50 do_syscall_64+0x34/0xb0 entry_SYSCALL_64_after_hwframe+0x63/0xcd The cause of the issue is that brelse() is called on both ofibh.sbh and ofibh.ebh by udf_find_entry() when it returns NULL. However, brelse() is called by udf_rename(), too. So, b_count on buffer_head becomes unbalanced. This patch fixes the issue by not calling brelse() by udf_rename() when udf_find_entry() returns NULL. Link: https://syzkaller.appspot.com/bug?id=3D8297f45698159c6bca8a1f87dc9836= 67c1a1c851 [1] Reported-by: syzbot+7902cd7684bc35306224@syzkaller.appspotmail.com Signed-off-by: Shigeru Yoshida --- fs/udf/namei.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/udf/namei.c b/fs/udf/namei.c index fb4c30e05245..d6081538bfc0 100644 --- a/fs/udf/namei.c +++ b/fs/udf/namei.c @@ -1091,8 +1091,9 @@ static int udf_rename(struct user_namespace *mnt_user= ns, struct inode *old_dir, return -EINVAL; =20 ofi =3D udf_find_entry(old_dir, &old_dentry->d_name, &ofibh, &ocfi); - if (IS_ERR(ofi)) { - retval =3D PTR_ERR(ofi); + if (!ofi || IS_ERR(ofi)) { + if (IS_ERR(ofi)) + retval =3D PTR_ERR(ofi); goto end_rename; } =20 @@ -1101,8 +1102,7 @@ static int udf_rename(struct user_namespace *mnt_user= ns, struct inode *old_dir, =20 brelse(ofibh.sbh); tloc =3D lelb_to_cpu(ocfi.icb.extLocation); - if (!ofi || udf_get_lb_pblock(old_dir->i_sb, &tloc, 0) - !=3D old_inode->i_ino) + if (udf_get_lb_pblock(old_dir->i_sb, &tloc, 0) !=3D old_inode->i_ino) goto end_rename; =20 nfi =3D udf_find_entry(new_dir, &new_dentry->d_name, &nfibh, &ncfi); --=20 2.37.3