BUG: unable to handle kernel NULL pointer dereference in page_mapping

[syzbot]

Hello,

syzkaller hit the following crash on
41d8c16909ebda40f7b4982a7f5e2ad102705ade
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


audit: type=1400 audit(1513163900.780:7): avc: denied { map } for
pid=3115 comm="syzkaller713832" path="/root/syzkaller713832919" dev="sda1"
ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
IP: __read_once_size include/linux/compiler.h:183 [inline]
IP: compound_head include/linux/page-flags.h:147 [inline]
IP: page_mapping+0x13/0x130 mm/util.c:475
PGD 214186067 P4D 214186067 PUD 213479067 PMD 0
Oops: 0000 [#1] SMP
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 3115 Comm: syzkaller713832 Not tainted
4.15.0-rc3-next-20171213+ #66
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:__read_once_size include/linux/compiler.h:183 [inline]
RIP: 0010:compound_head include/linux/page-flags.h:147 [inline]
RIP: 0010:page_mapping+0x13/0x130 mm/util.c:475
RSP: 0018:ffffc900017abb98 EFLAGS: 00010293
RAX: ffff880213652240 RBX: 0000000000000000 RCX: ffffffff81377f83
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900017abbb8 R08: 0000000000000000 R09: ffff8802164af250
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8802164af180
R13: ffff8802164af000 R14: ffff88020db7b7c0 R15: ffff880213404730
FS: 00000000021c7880(0000) GS:ffff88021fd00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000020 CR3: 000000021364f000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
set_page_dirty+0x1b/0x150 mm/page-writeback.c:2544
rds_atomic_free_op+0x25/0x80 net/rds/rdma.c:481
rds_message_purge net/rds/message.c:79 [inline]
rds_message_put+0x174/0x1b0 net/rds/message.c:91
rds_sendmsg+0x7ac/0xcb0 net/rds/send.c:1204
sock_sendmsg_nosec net/socket.c:636 [inline]
sock_sendmsg+0x51/0x70 net/socket.c:646
___sys_sendmsg+0x35e/0x3b0 net/socket.c:2026
__sys_sendmsg+0x50/0x90 net/socket.c:2060
SYSC_sendmsg net/socket.c:2071 [inline]
SyS_sendmsg+0x2d/0x50 net/socket.c:2067
entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x4400a9
RSP: 002b:00007fff97b55488 EFLAGS: 00000217 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004400a9
RDX: 0000000000000040 RSI: 000000002048cfe4 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000217 R12: 0000000000401a10
R13: 0000000000401aa0 R14: 0000000000000000 R15: 0000000000000000
Code: 14 24 f4 ff 48 c7 c7 c8 57 a4 82 e8 46 01 24 01 0f 1f 84 00 00 00 00
00 55 48 89 e5 41 56 41 55 41 54 53 48 89 fb e8 ed 23 f4 ff <4c> 8b 63 20
41 f6 c4 01 0f 85 c8 00 00 00 e8 da 23 f4 ff 4c 8b
RIP: __read_once_size include/linux/compiler.h:183 [inline] RSP:
ffffc900017abb98
RIP: compound_head include/linux/page-flags.h:147 [inline] RSP:
ffffc900017abb98
RIP: page_mapping+0x13/0x130 mm/util.c:475 RSP: ffffc900017abb98
CR2: 0000000000000020
---[ end trace 35e760b7322fed80 ]---


---
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[Eric Biggers]

Crash is no longer occurring, was fixed by commit 7d11f77f84b27:

#syz fix: RDS: null pointer dereference in rds_atomic_free_op