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BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter

Status: fixed on 2019/03/28 12:00
Subsystems: fs mm
[Documentation on labels]
Reported-by: syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com
Fix commit: ac5ceccce550 x86/unwind: Add hardcoded ORC entry for NULL f4f34e1b82eb x86/unwind: Handle NULL pointer calls better in frame unwinder
First crash: 2469d, last: 2313d
▶ ▼ Discussions (5)
Title Replies (including bot) Last reply
[PATCH 5.0 00/52] 5.0.5-stable review 61 (61) 2019/03/27 05:06
[PATCH 4.19 00/45] 4.19.32-stable review 51 (51) 2019/03/27 04:04
[PATCH 4.14 00/41] 4.14.109-stable review 47 (47) 2019/03/26 23:15
[PATCH 1/2] x86/unwind: handle NULL pointer calls better in frame unwinder 11 (11) 2019/03/06 22:31
BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter 6 (7) 2019/03/01 03:31
▶ ▼ Similar bugs (1)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter (2) ntfs3 C 8 149d 182d 28/29 fixed on 2025/06/10 16:19

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
#PF error: [INSTR]
PGD 918fe067 P4D 918fe067 PUD a9248067 PMD 0 
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 12468 Comm: syz-executor.3 Not tainted 5.0.0-rc8+ #88
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:          (null)
Code: Bad RIP value.
RSP: 0018:ffff88804ccdf9b8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000018
RDX: 0000000000000000 RSI: ffff8880442dc9f0 RDI: ffff888085cf9c80
RBP: ffff88804ccdfad0 R08: 0000000000000000 R09: ffff88804ccdfa48
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000018
R13: ffffffff877ae9a0 R14: ffff88804ccdfaa8 R15: ffff8880442dc9f0
FS:  00007f4e9fe4d700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 00000000a4d70000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 __generic_file_write_iter+0x25e/0x630 mm/filemap.c:3333
 ext4_file_write_iter+0x33f/0x1160 fs/ext4/file.c:266
 call_write_iter include/linux/fs.h:1863 [inline]
 new_sync_write fs/read_write.c:474 [inline]
 __vfs_write+0x613/0x8e0 fs/read_write.c:487
 vfs_write+0x20c/0x580 fs/read_write.c:549
 ksys_write+0xea/0x1f0 fs/read_write.c:598
 __do_sys_write fs/read_write.c:610 [inline]
 __se_sys_write fs/read_write.c:607 [inline]
 __x64_sys_write+0x73/0xb0 fs/read_write.c:607
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457e29
Code: ad b8 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 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f4e9fe4cc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457e29
RDX: 0000000000000018 RSI: 0000000020000140 RDI: 0000000000000008
RBP: 000000000073bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f4e9fe4d6d4
R13: 00000000004c6ca2 R14: 00000000004dc530 R15: 00000000ffffffff
Modules linked in:
CR2: 0000000000000000
---[ end trace 65c82dcf04efd9f6 ]---
RIP: 0010:          (null)
kobject: 'loop5' (00000000c074be4c): kobject_uevent_env
Code: Bad RIP value.
kobject: 'loop4' (000000001e6074c4): kobject_uevent_env
kobject: 'loop5' (00000000c074be4c): fill_kobj_path: path = '/devices/virtual/block/loop5'
kobject: 'loop4' (000000001e6074c4): fill_kobj_path: path = '/devices/virtual/block/loop4'
RSP: 0018:ffff88804ccdf9b8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000018
RDX: 0000000000000000 RSI: ffff8880442dc9f0 RDI: ffff888085cf9c80
RBP: ffff88804ccdfad0 R08: 0000000000000000 R09: ffff88804ccdfa48
kobject: 'loop0' (000000000cd03e85): kobject_uevent_env
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000018
kobject: 'loop0' (000000000cd03e85): fill_kobj_path: path = '/devices/virtual/block/loop0'
R13: ffffffff877ae9a0 R14: ffff88804ccdfaa8 R15: ffff8880442dc9f0
FAULT_INJECTION: forcing a failure.
name failslab, interval 1, probability 0, space 0, times 0
FS:  00007f4e9fe4d700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CPU: 0 PID: 12458 Comm: syz-executor.0 Tainted: G      D           5.0.0-rc8+ #88
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 fail_dump lib/fault-inject.c:51 [inline]
 should_fail.cold+0xa/0x1b lib/fault-inject.c:149
CR2: 0000000000c099b8 CR3: 00000000a4d70000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 __should_failslab+0x121/0x190 mm/failslab.c:32
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 should_failslab+0x9/0x14 mm/slab_common.c:1604
 slab_pre_alloc_hook mm/slab.h:423 [inline]
 slab_alloc_node mm/slab.c:3295 [inline]
 kmem_cache_alloc_node_trace+0x270/0x720 mm/slab.c:3655

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2019/03/01 21:06 upstream 7d762d69145a 68d9e495 .config console log report ci-upstream-kasan-gce-smack-root
2019/01/29 17:39 upstream 4aa9fc2a435a aa432daf .config console log report ci-upstream-kasan-gce-selinux-root
2019/01/16 07:22 upstream 7939f8beecf1 b47fa78d .config console log report ci-upstream-kasan-gce-smack-root
2018/10/16 06:54 upstream f0a7d1883d9f 8cd30605 .config console log report ci-upstream-kasan-gce-selinux-root
2018/09/26 05:30 linux-next 8b7a6ebdd4a5 b7e11289 .config console log report ci-upstream-linux-next-kasan-gce-root
* Struck through repros no longer work on HEAD.