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BUG: unable to handle kernel NULL pointer dereference in generic_perform_write (2)

Status: fixed on 2020/07/21 02:08
Reported-by: syzbot+9ff97b23546cea824ecf@syzkaller.appspotmail.com
Fix commit: 5dbb625573ab ext4: avoid race conditions when remounting with options that change dax
First crash: 1494d, last: 1404d
Fix bisection: fixed by (bisect log) :
commit 5dbb625573abf67b9f7d6992c8e3f57acaef5946
Author: Theodore Ts'o <tytso@mit.edu>
Date: Wed Jun 10 15:16:37 2020 +0000

  ext4: avoid race conditions when remounting with options that change dax

  
▶ ▼ Similar bugs (3)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream BUG: unable to handle kernel NULL pointer dereference in generic_perform_write (2) ext4 C done 3 1474d 1472d 15/26 fixed on 2020/07/17 17:58
linux-4.19 BUG: unable to handle kernel NULL pointer dereference in generic_perform_write 2 1659d 1741d 0/1 auto-closed as invalid on 2020/02/07 03:38
upstream BUG: unable to handle kernel NULL pointer dereference in generic_perform_write ext4 2 1638d 1695d 0/26 auto-closed as invalid on 2020/01/28 20:19
▶ ▼ Fix bisection attempts (4)
Created Duration User Patch Repo Result
2020/07/20 20:42 3h40m bisect fix linux-4.19.y job log (1)
2020/06/20 20:01 26m bisect fix linux-4.19.y job log (0) log
2020/05/21 19:35 26m bisect fix linux-4.19.y job log (0) log
2020/04/21 19:07 27m bisect fix linux-4.19.y job log (0) log

Sample crash report:
EXT4-fs (sda1): DAX enabled. Warning: EXPERIMENTAL, use at your own risk
EXT4-fs (sda1): warning: refusing change of dax flag with busy inodes while remounting
EXT4-fs (sda1): re-mounted. Opts: dax,
BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
PGD 9f2b2067 P4D 9f2b2067 PUD 8f553067 PMD 0 
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 8210 Comm: syz-executor102 Not tainted 4.19.112-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:          (null)
Code: Bad RIP value.
RSP: 0018:ffff888086f97a70 EFLAGS: 00010246
RAX: ffffffff877a42c0 RBX: 0000000000000000 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffff8880933cd4f0 RDI: ffff8880874347c0
EXT4-fs (sda1): DAX enabled. Warning: EXPERIMENTAL, use at your own risk
RBP: ffff8880933cd4f0 R08: 0000000000000000 R09: ffff888086f97af0
R10: ffffed1012679a99 R11: ffff8880933cd4cf R12: 0000000000000001
R13: 0000000000000000 R14: ffff888086f97d90 R15: 0000000000000000
FS:  00007f3f4e48f700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000008f549000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
EXT4-fs (sda1): warning: refusing change of dax flag with busy inodes while remounting
 generic_perform_write+0x1f8/0x4d0 mm/filemap.c:3162
 __generic_file_write_iter+0x24c/0x610 mm/filemap.c:3287
 ext4_file_write_iter+0x2fe/0xf90 fs/ext4/file.c:272
 call_write_iter include/linux/fs.h:1820 [inline]
 new_sync_write fs/read_write.c:474 [inline]
 __vfs_write+0x512/0x760 fs/read_write.c:487
 vfs_write+0x206/0x550 fs/read_write.c:549
 ksys_write+0x12b/0x2a0 fs/read_write.c:599
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x44e7a9
Code: 4d c9 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 1b c9 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f3f4e48ece8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000006e1c28 RCX: 000000000044e7a9
RDX: 0000000000000001 RSI: 0000000020000080 RDI: 0000000000000003
RBP: 00000000006e1c20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006e1c2c
R13: 00007ffee3bf9daf R14: 00007f3f4e48f9c0 R15: 0000000000000000
Modules linked in:
CR2: 0000000000000000
EXT4-fs (sda1): re-mounted. Opts: dax,
---[ end trace 110f166ba9f5c89b ]---
RIP: 0010:          (null)
Code: Bad RIP value.
RSP: 0018:ffff888086f97a70 EFLAGS: 00010246
RAX: ffffffff877a42c0 RBX: 0000000000000000 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffff8880933cd4f0 RDI: ffff8880874347c0
RBP: ffff8880933cd4f0 R08: 0000000000000000 R09: ffff888086f97af0
R10: ffffed1012679a99 R11: ffff8880933cd4cf R12: 0000000000000001
R13: 0000000000000000 R14: ffff888086f97d90 R15: 0000000000000000
FS:  00007f3f4e48f700(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9aebe7e518 CR3: 000000008f549000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
EXT4-fs (sda1): DAX enabled. Warning: EXPERIMENTAL, use at your own risk

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/03/22 19:07 linux-4.19.y 14cfdbd39e31 78267cec .config console log report syz C ci2-linux-4-19
* Struck through repros no longer work on HEAD.