On Wed 22-12-21 15:47:12, Lukas Czerner wrote:
> On Wed, Dec 22, 2021 at 03:37:57PM +0100, Jan Kara wrote:
> > On Wed 22-12-21 09:35:37, Ye Bin wrote:
> > > We got issue as follows when run syzkaller:
> > > [ 167.936972] EXT4-fs error (device loop0): __ext4_remount:6314: comm rep: Abort forced by user
> > > [ 167.938306] EXT4-fs (loop0): Remounting filesystem read-only
> > > [ 167.981637] Assertion failure in ext4_getblk() at fs/ext4/inode.c:847: '(EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY) || handle != NULL || create == 0'
> > > [ 167.983601] ------------[ cut here ]------------
> > > [ 167.984245] kernel BUG at fs/ext4/inode.c:847!
> > > [ 167.984882] invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
> > > [ 167.985624] CPU: 7 PID: 2290 Comm: rep Tainted: G B 5.16.0-rc5-next-20211217+ #123
> > > [ 167.986823] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 04/01/2014
> > > [ 167.988590] RIP: 0010:ext4_getblk+0x17e/0x504
> > > [ 167.989189] Code: c6 01 74 28 49 c7 c0 a0 a3 5c 9b b9 4f 03 00 00 48 c7 c2 80 9c 5c 9b 48 c7 c6 40 b6 5c 9b 48 c7 c7 20 a4 5c 9b e8 77 e3 fd ff <0f> 0b 8b 04 244
> > > [ 167.991679] RSP: 0018:ffff8881736f7398 EFLAGS: 00010282
> > > [ 167.992385] RAX: 0000000000000094 RBX: 1ffff1102e6dee75 RCX: 0000000000000000
> > > [ 167.993337] RDX: 0000000000000001 RSI: ffffffff9b6e29e0 RDI: ffffed102e6dee66
> > > [ 167.994292] RBP: ffff88816a076210 R08: 0000000000000094 R09: ffffed107363fa09
> > > [ 167.995252] R10: ffff88839b1fd047 R11: ffffed107363fa08 R12: ffff88816a0761e8
> > > [ 167.996205] R13: 0000000000000000 R14: 0000000000000021 R15: 0000000000000001
> > > [ 167.997158] FS: 00007f6a1428c740(0000) GS:ffff88839b000000(0000) knlGS:0000000000000000
> > > [ 167.998238] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > [ 167.999025] CR2: 00007f6a140716c8 CR3: 0000000133216000 CR4: 00000000000006e0
> > > [ 167.999987] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > [ 168.000944] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > [ 168.001899] Call Trace:
> > > [ 168.002235] <TASK>
> > > [ 168.007167] ext4_bread+0xd/0x53
> > > [ 168.007612] ext4_quota_write+0x20c/0x5c0
> > > [ 168.010457] write_blk+0x100/0x220
> > > [ 168.010944] remove_free_dqentry+0x1c6/0x440
> > > [ 168.011525] free_dqentry.isra.0+0x565/0x830
> > > [ 168.012133] remove_tree+0x318/0x6d0
> > > [ 168.014744] remove_tree+0x1eb/0x6d0
> > > [ 168.017346] remove_tree+0x1eb/0x6d0
> > > [ 168.019969] remove_tree+0x1eb/0x6d0
> > > [ 168.022128] qtree_release_dquot+0x291/0x340
> > > [ 168.023297] v2_release_dquot+0xce/0x120
> > > [ 168.023847] dquot_release+0x197/0x3e0
> > > [ 168.024358] ext4_release_dquot+0x22a/0x2d0
> > > [ 168.024932] dqput.part.0+0x1c9/0x900
> > > [ 168.025430] __dquot_drop+0x120/0x190
> > > [ 168.025942] ext4_clear_inode+0x86/0x220
> > > [ 168.026472] ext4_evict_inode+0x9e8/0xa22
> > > [ 168.028200] evict+0x29e/0x4f0
> > > [ 168.028625] dispose_list+0x102/0x1f0
> > > [ 168.029148] evict_inodes+0x2c1/0x3e0
> > > [ 168.030188] generic_shutdown_super+0xa4/0x3b0
> > > [ 168.030817] kill_block_super+0x95/0xd0
> > > [ 168.031360] deactivate_locked_super+0x85/0xd0
> > > [ 168.031977] cleanup_mnt+0x2bc/0x480
> > > [ 168.033062] task_work_run+0xd1/0x170
> > > [ 168.033565] do_exit+0xa4f/0x2b50
> > > [ 168.037155] do_group_exit+0xef/0x2d0
> > > [ 168.037666] __x64_sys_exit_group+0x3a/0x50
> > > [ 168.038237] do_syscall_64+0x3b/0x90
> > > [ 168.038751] entry_SYSCALL_64_after_hwframe+0x44/0xae
> > >
> > > In order to reproduce this problem, the following conditions need to be met:
> > > 1. Ext4 filesystem with no journal;
> > > 2. Filesystem image with incorrect quota data;
> > > 3. Abort filesystem forced by user;
> > > 4. umount filesystem;
> > >
> > > As in ext4_quota_write:
> > > ...
> > > if (EXT4_SB(sb)->s_journal && !handle) {
> > > ext4_msg(sb, KERN_WARNING, "Quota write (off=%llu, len=%llu)"
> > > " cancelled because transaction is not started",
> > > (unsigned long long)off, (unsigned long long)len);
> > > return -EIO;
> > > }
> > > ...
> > > We only check handle if NULL when filesystem has journal. There is need
> > > check handle if NULL even when filesystem has no journal.
> >
> > Hum, so I think we can just drop this whole condition and warning and
> > instead add a silent return of -EROFS if the filesystem is readonly. That
> > should also fix the bug and also make aborted case less noisy. The message
> > from ext4_quota_write() IMO is not very useful and ext4_bread() will
> > provide us with a BUG and stacktrace which is better for debugging what
> > went wrong anyway.
>
> Can we really only get here when the fs is read only ? We're going to
> end up with NULL handle here any time the ext4_journal_start() fails in
> ext4_release_dquot() which I think can fail for plenty of reasons, not
> just EROFS.
Hum, that's good point. So probably Ye Bin's patch is as good as it gets :)
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
