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Thu, 05 Aug 2021 07:26:24 -0700 (PDT) Subject: Re: [syzbot] INFO: task hung in ext4_fill_super To: syzbot , adilger.kernel@dilger.ca, clang-built-linux@googlegroups.com, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, nathan@kernel.org, ndesaulniers@google.com, syzkaller-bugs@googlegroups.com, tytso@mit.edu References: <0000000000004c80e405c4df1a2d@google.com> From: Pavel Skripkin Message-ID: <1e291320-3ad3-aa21-77c6-c71da9d32fdb@gmail.com> Date: Thu, 5 Aug 2021 17:26:22 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <0000000000004c80e405c4df1a2d@google.com> Content-Type: multipart/mixed; boundary="------------675893B3B0BF5C1099A6646E" Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org This is a multi-part message in MIME format. --------------675893B3B0BF5C1099A6646E Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit On 6/16/21 12:56 PM, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: f21b807c Merge tag 'drm-fixes-2021-06-11' of git://anongit.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=165fca57d00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=30f476588412c065 > dashboard link: https://syzkaller.appspot.com/bug?extid=c9ff4822a62eee994ea3 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17d19ce0300000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=108d7988300000 > > Bisection is inconclusive: the issue happens on the oldest tested release. > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1646b8d0300000 > final oops: https://syzkaller.appspot.com/x/report.txt?x=1546b8d0300000 > console output: https://syzkaller.appspot.com/x/log.txt?x=1146b8d0300000 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+c9ff4822a62eee994ea3@syzkaller.appspotmail.com > > INFO: task syz-executor768:8567 blocked for more than 143 seconds. > Not tainted 5.13.0-rc5-syzkaller #0 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > task:syz-executor768 state:D stack:27544 pid: 8567 ppid: 8423 flags:0x00004004 > Call Trace: > context_switch kernel/sched/core.c:4339 [inline] > __schedule+0x916/0x23e0 kernel/sched/core.c:5147 > schedule+0xcf/0x270 kernel/sched/core.c:5226 > schedule_timeout+0x1db/0x250 kernel/time/timer.c:1868 > do_wait_for_common kernel/sched/completion.c:85 [inline] > __wait_for_common kernel/sched/completion.c:106 [inline] > wait_for_common kernel/sched/completion.c:117 [inline] > wait_for_completion+0x168/0x270 kernel/sched/completion.c:138 > kthread_stop+0x17a/0x720 kernel/kthread.c:642 > ext4_fill_super+0x87ac/0xdfa0 fs/ext4/super.c:5190 > mount_bdev+0x34d/0x410 fs/super.c:1368 > legacy_get_tree+0x105/0x220 fs/fs_context.c:592 > vfs_get_tree+0x89/0x2f0 fs/super.c:1498 > do_new_mount fs/namespace.c:2905 [inline] > path_mount+0x132a/0x1fa0 fs/namespace.c:3235 > do_mount fs/namespace.c:3248 [inline] > __do_sys_mount fs/namespace.c:3456 [inline] > __se_sys_mount fs/namespace.c:3433 [inline] > __x64_sys_mount+0x27f/0x300 fs/namespace.c:3433 > do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47 > entry_SYSCALL_64_after_hwframe+0x44/0xae > RIP: 0033:0x445b2a > RSP: 002b:00007ffc5efbf598 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5 > RAX: ffffffffffffffda RBX: 00007ffc5efbf5f0 RCX: 0000000000445b2a > RDX: 0000000020000000 RSI: 00000000200000c0 RDI: 00007ffc5efbf5b0 > RBP: 00007ffc5efbf5b0 R08: 00007ffc5efbf5f0 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000202 R12: 00000000200003f8 > R13: 0000000000000003 R14: 0000000000000004 R15: 0000000000000005 > #syz test git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master With regards, Pavel Skripkin --------------675893B3B0BF5C1099A6646E Content-Type: text/x-patch; charset=UTF-8; name="0001-ext4-avoid-huge-mmp-update-interval-value.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="0001-ext4-avoid-huge-mmp-update-interval-value.patch" >From 9eb3e2f727e1c33ec39c28694a1528b9cc4a32eb Mon Sep 17 00:00:00 2001 From: Pavel Skripkin Date: Thu, 5 Aug 2021 17:23:40 +0300 Subject: [PATCH] ext4: avoid huge mmp update interval value /* .. */ Signed-off-by: Pavel Skripkin --- fs/ext4/mmp.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c index bc364c119af6..2f632344d38c 100644 --- a/fs/ext4/mmp.c +++ b/fs/ext4/mmp.c @@ -7,6 +7,9 @@ #include "ext4.h" +#define EXT4_KMMP_MAX_INTERVAL 100 +#define EXT4_KMMP_MIN_INTERVAL 5 + /* Checksumming functions */ static __le32 ext4_mmp_csum(struct super_block *sb, struct mmp_struct *mmp) { @@ -140,6 +143,11 @@ static int kmmpd(void *data) unsigned long diff; int retval; + /* We should avoid unreasonale huge update interval, since it can cause + * task hung bug on umount or on error handling path in ext4_fill_super() + */ + mmp_update_interval = clamp(mmp_update_interval, EXT4_KMMP_MIN_INTERVAL, EXT4_KMMP_MAX_INTERVAL); + mmp_block = le64_to_cpu(es->s_mmp_block); mmp = (struct mmp_struct *)(bh->b_data); mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds()); @@ -156,6 +164,9 @@ static int kmmpd(void *data) memcpy(mmp->mmp_nodename, init_utsname()->nodename, sizeof(mmp->mmp_nodename)); + ext4_msg(sb, KERN_INFO, "Started kmmp thread with update interval = %u\n", + mmp_update_interval); + while (!kthread_should_stop() && !sb_rdonly(sb)) { if (!ext4_has_feature_mmp(sb)) { ext4_warning(sb, "kmmpd being stopped since MMP feature" -- 2.32.0 --------------675893B3B0BF5C1099A6646E--