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@xxxxxxxxxxxxxxxxxxxxxxxxx
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
>From 9eb3e2f727e1c33ec39c28694a1528b9cc4a32eb Mon Sep 17 00:00:00 2001
From: Pavel Skripkin <paskripkin@xxxxxxxxx>
Date: Thu, 5 Aug 2021 17:23:40 +0300
Subject: [PATCH] ext4: avoid huge mmp update interval value
/* .. */
Signed-off-by: Pavel Skripkin <paskripkin@xxxxxxxxx>
---
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
