BUG: unable to handle kernel NULL pointer dereference in __generic_file_write

BUG: unable to handle kernel NULL pointer dereference in __generic_file_write_iter
Status: fixed on 2019/03/28 12:00
Reported-by: syzbot+ca95b2b7aef9e7cbd6ab@syzkaller.appspotmail.com
Fix commit: ac5ceccc x86/unwind: Add hardcoded ORC entry for NULL f4f34e1b x86/unwind: Handle NULL pointer calls better in frame unwinder
First crash: 645d, last: 488d

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):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Maintainers
ci-upstream-kasan-gce-smack-root	2019/03/01 21:06	upstream	7d762d69	68d9e495	.config	log	report	akpm@linux-foundation.org, amir73il@gmail.com, darrick.wong@oracle.com, david@fromorbit.com, hannes@cmpxchg.org, hughd@google.com, jrdr.linux@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, willy@infradead.org
ci-upstream-kasan-gce-selinux-root	2019/01/29 17:39	upstream	4aa9fc2a	aa432daf	.config	log	report	akpm@linux-foundation.org, amir73il@gmail.com, darrick.wong@oracle.com, david@fromorbit.com, hannes@cmpxchg.org, hughd@google.com, jrdr.linux@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, willy@infradead.org
ci-upstream-kasan-gce-smack-root	2019/01/16 07:22	upstream	7939f8be	b47fa78d	.config	log	report	akpm@linux-foundation.org, amir73il@gmail.com, darrick.wong@oracle.com, david@fromorbit.com, hannes@cmpxchg.org, hughd@google.com, jrdr.linux@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, willy@infradead.org
ci-upstream-kasan-gce-selinux-root	2018/10/16 06:54	upstream	f0a7d188	8cd30605	.config	log	report	ak@linux.intel.com, akpm@linux-foundation.org, arnd@arndb.de, dhowells@redhat.com, jack@suse.cz, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mawilcox@microsoft.com, mgorman@techsingularity.net
ci-upstream-linux-next-kasan-gce-root	2018/09/26 05:30	linux-next	8b7a6ebd	b7e11289	.config	log	report	akpm@linux-foundation.org, hannes@cmpxchg.org, jack@suse.cz, jrdr.linux@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mawilcox@microsoft.com, mgorman@techsingularity.net, sfr@canb.auug.org.au