* [BUG]NULL pointer dereference at 0000000000000008 __blkdev_put+0x17f/0x1d0
@ 2013-12-30 15:55 Jack Wang
2014-01-02 9:36 ` Jack Wang
0 siblings, 1 reply; 4+ messages in thread
From: Jack Wang @ 2013-12-30 15:55 UTC (permalink / raw)
To: Alexander Viro, linux-fsdevel, linux-kernel@vger.kernel.org
Hi,
We saw NULL pointer dereference below:
Dec 28 16:24:26 server kernel: [979193.076399] BUG: unable to handle
kernel NULL pointer dereference at 0000000000000008
Dec 28 16:24:26 server kernel: [979193.076401] IP: [<ffffffff8116952f>]
__blkdev_put+0x17f/0x1d0
Dec 28 16:24:26 server kernel: [979193.076408] PGD 4bdcaa067 PUD
4bdc43067 PMD 0
Dec 28 16:24:26 server kernel: [979193.076410] Oops: 0000 [#1] SMP
Dec 28 16:24:26 server kernel: [979193.076412] CPU 6
Dec 28 16:24:26 server kernel: [979193.076413] Modules linked in: bridge
stp llc nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables
raid1 md_mod dm_round_robin sd_mod crc_t10dif ib_srp scsi_transport_srp
scsi_tgt xt_ETHOIP6(O) x_tables vhost_net(O) macvtap macvlan tun(O)
nf_conntrack_ipv4 nf_conntrack nf_defrag_ipv4 rdma_ucm rdma_cm iw_cm
ib_addr ib_ipoib ib_cm ib_sa ib_uverbs ib_umad ib_qib mlx4_ib ib_mthca
ib_mad ib_core dm_multipath scsi_dh scsi_mod kvm_amd kvm powernow_k8
mperf psmouse crc32c_intel microcode tpm_tis tpm tpm_bios serio_raw
evdev amd64_edac_mod edac_core edac_mce_amd i2c_piix4 button processor
thermal_sys mlx4_core
Dec 28 16:24:26 server kernel: [979193.076440]
Dec 28 16:24:26 server kernel: [979193.076442] Pid: 56544, comm:
multipath Tainted: G O 3.4.71-3-pserver #1 Supermicro BHQGE/BHQGE
Dec 28 16:24:26 server kernel: [979193.076445] RIP:
0010:[<ffffffff8116952f>] [<ffffffff8116952f>] __blkdev_put+0x17f/0x1d0
Dec 28 16:24:26 server kernel: [979193.076448] RSP:
0018:ffff882802f4beb8 EFLAGS: 00010246
Dec 28 16:24:26 server kernel: [979193.076449] RAX: 0000000000000000
RBX: ffff881ff78b0d00 RCX: 0000000000000001
Dec 28 16:24:26 server kernel: [979193.076451] RDX: 0000000000000000
RSI: 000000000000001d RDI: ffff881ff78b0d18
Dec 28 16:24:26 server kernel: [979193.076452] RBP: 0000000000000000
R08: 0000000000000000 R09: 0000000000000000
Dec 28 16:24:26 server kernel: [979193.076453] R10: 0000000000000000
R11: 0000000000000246 R12: 000000000000001d
Dec 28 16:24:26 server kernel: [979193.076455] R13: ffff881ff78b0d18
R14: ffff8807f9e7f400 R15: ffff8804a8d77710
Dec 28 16:24:26 server kernel: [979193.076457] FS:
00007ff8c80fe7a0(0000) GS:ffff880807d80000(0000) knlGS:0000000000000000
Dec 28 16:24:26 server kernel: [979193.076458] CS: 0010 DS: 0000 ES:
0000 CR0: 0000000080050033
Dec 28 16:24:26 server kernel: [979193.076460] CR2: 0000000000000008
CR3: 000000064765f000 CR4: 00000000000407e0
Dec 28 16:24:26 server kernel: [979193.076461] DR0: 0000000000000000
DR1: 0000000000000000 DR2: 0000000000000000
Dec 28 16:24:26 server kernel: [979193.076463] DR3: 0000000000000000
DR6: 00000000ffff0ff0 DR7: 0000000000000400
Dec 28 16:24:26 server kernel: [979193.076464] Process multipath (pid:
56544, threadinfo ffff882802f4a000, task ffff8828020106d0)
Dec 28 16:24:26 server kernel: [979193.076466] Stack:
Dec 28 16:24:26 server kernel: [979193.076466] 0000000000000000
0000000000000000 ffff880803cf2580 ffff8804a8d77700
Dec 28 16:24:26 server kernel: [979193.076468] 0000000000000010
ffff88100363eff0 ffff881004609b00 ffff882003c20020
Dec 28 16:24:26 server kernel: [979193.076470] ffff8804a8d77710
ffffffff81136bad 00007fffbdc8f420 ffff8804a8d77700
Dec 28 16:24:26 server kernel: [979193.076472] Call Trace:
Dec 28 16:24:26 server kernel: [979193.076477] [<ffffffff81136bad>] ?
fput+0xdd/0x270
Dec 28 16:24:26 server kernel: [979193.076479] [<ffffffff81132f0c>] ?
filp_close+0x5c/0x90
Dec 28 16:24:26 server kernel: [979193.076481] [<ffffffff81132fb1>] ?
sys_close+0x71/0xc0
Dec 28 16:24:26 server kernel: [979193.076484] [<ffffffff816801b9>] ?
system_call_fastpath+0x16/0x1b
Dec 28 16:24:26 server kernel: [979193.076486] Code: 8b 5c 24 18 48 8b
6c 24 20 4c 8b 64 24 28 4c 8b 6c 24 30 4c 8b 74 24 38 4c 8b 7c 24 40 48
83 c4 48 c3 66 90 49 8b 86 48 03 00 00 <48> 8b 40 08 48 85 c0 0f 84 fc
fe ff ff 44 89 e6 4c 89 f7 ff d0
Dec 28 16:24:26 server kernel: [979193.076500] RIP [<ffffffff8116952f>]
__blkdev_put+0x17f/0x1d0
Dec 28 16:24:26 server kernel: [979193.076503] RSP <ffff882802f4beb8>
Dec 28 16:24:26 server kernel: [979193.076504] CR2: 0000000000000008
Dec 28 16:24:26 server kernel: [979193.077599] ---[ end trace
23f39da823d257f9 ]---
disassamble results show:
1465 static int __blkdev_put(struct block_device *bdev, fmode_t mode,
int for_part)
1466 {
0xffffffff81162d10 <+0>: sub $0x48,%rsp
0xffffffff81162d14 <+4>: mov %r13,0x30(%rsp)
0xffffffff81162d1d <+13>: mov %rbx,0x18(%rsp)
0xffffffff81162d22 <+18>: mov %rbp,0x20(%rsp)
0xffffffff81162d27 <+23>: mov %r12,0x28(%rsp)
0xffffffff81162d2c <+28>: mov %edx,%ebp
0xffffffff81162d2e <+30>: mov %r14,0x38(%rsp)
0xffffffff81162d33 <+35>: mov %r15,0x40(%rsp)
0xffffffff81162d38 <+40>: mov %rdi,%rbx
0xffffffff81162d45 <+53>: mov %esi,%r12d
1467 int ret = 0;
0xffffffff81162d8e <+126>: xor %ebp,%ebp
1468 struct gendisk *disk = bdev->bd_disk;
0xffffffff81162d3b <+43>: mov 0x90(%rdi),%r14
1469 struct block_device *victim = NULL;
1470
1471 mutex_lock_nested(&bdev->bd_mutex, for_part);
0xffffffff81162d19 <+9>: lea 0x18(%rdi),%r13
---Type <return> to continue, or q <return> to quit---
0xffffffff81162d42 <+50>: mov %r13,%rdi
0xffffffff81162d48 <+56>: callq 0xffffffff8166ece0 <mutex_lock>
1472 if (for_part)
0xffffffff81162d4d <+61>: test %ebp,%ebp
0xffffffff81162d4f <+63>: je 0xffffffff81162d57 <__blkdev_put+71>
1473 bdev->bd_part_count--;
0xffffffff81162d51 <+65>: decl 0x88(%rbx)
1474
1475 if (!--bdev->bd_openers) {
0xffffffff81162d57 <+71>: mov 0x4(%rbx),%eax
0xffffffff81162d5a <+74>: dec %eax
0xffffffff81162d5c <+76>: test %eax,%eax
0xffffffff81162d5e <+78>: mov %eax,0x4(%rbx)
0xffffffff81162d61 <+81>: jne 0xffffffff81162d8e <__blkdev_put+126>
1476 WARN_ON_ONCE(bdev->bd_holders);
0xffffffff81162d63 <+83>: mov 0x58(%rbx),%edx
0xffffffff81162d66 <+86>: test %edx,%edx
0xffffffff81162d68 <+88>: jne 0xffffffff81162e9b <__blkdev_put+395>
0xffffffff81162e9b <+395>: cmpb $0x1,0x936b1e(%rip) #
0xffffffff81a999c0 <__warned.29603>
0xffffffff81162ea2 <+402>: je 0xffffffff81162d6e <__blkdev_put+94>
0xffffffff81162ea8 <+408>: mov $0x5c4,%esi
0xffffffff81162ead <+413>: mov $0xffffffff8193f5a7,%rdi
0xffffffff81162eb4 <+420>: callq 0xffffffff81036ee0 <warn_slowpath_null>
0xffffffff81162eb9 <+425>: movb $0x1,0x936b00(%rip) #
0xffffffff81a999c0 <__warned.29603>
0xffffffff81162ec0 <+432>: jmpq 0xffffffff81162d6e <__blkdev_put+94>
0xffffffff81162ec5: data32 nopw %cs:0x0(%rax,%rax,1)
1484 }
1485 if (bdev->bd_contains == bdev) {
0xffffffff81162d90 <+128>: cmp %rbx,0x70(%rbx)
0xffffffff81162d94 <+132>: je 0xffffffff81162e78 <__blkdev_put+360>
1486 if (disk->fops->release)
---Type <return> to continue, or q <return> to quit---
0xffffffff81162e78 <+360>: mov 0x348(%r14),%raxat
0xffffffff81162e7f <+367>: mov 0x8(%rax),%rax
0xffffffff81162e83 <+371>: test %rax,%rax
0xffffffff81162e86 <+374>: je 0xffffffff81162d9a <__blkdev_put+138>
1487 ret = disk->fops->release(disk, mode);
0xffffffff81162e8c <+380>: mov %r12d,%esi
0xffffffff81162e8f <+383>: mov %r14,%rdi
0xffffffff81162e92 <+386>: callq *%rax
0xffffffff81162e94 <+388>: mov %eax,%ebp
0xffffffff81162e96 <+390>: jmpq 0xffffffff81162d9a <__blkdev_put+138>
snip
Bug happened at line 1486, looks disk->fops is NULL here for some
reason, is it reasonable to add a check like:
if (disk->fops)
if (disk->fops->release)
ret = disk->fops->release(disk, mode);
Happy New Year and Best regards:)
Jack
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [BUG]NULL pointer dereference at 0000000000000008 __blkdev_put+0x17f/0x1d0 2013-12-30 15:55 [BUG]NULL pointer dereference at 0000000000000008 __blkdev_put+0x17f/0x1d0 Jack Wang @ 2014-01-02 9:36 ` Jack Wang 2014-01-04 6:09 ` Al Viro 0 siblings, 1 reply; 4+ messages in thread From: Jack Wang @ 2014-01-02 9:36 UTC (permalink / raw) To: Alexander Viro, linux-fsdevel, linux-kernel@vger.kernel.org, Jens Axboe [-- Attachment #1: Type: text/plain, Size: 8107 bytes --] On 12/30/2013 04:55 PM, Jack Wang wrote: > Hi, > > We saw NULL pointer dereference below: > > Dec 28 16:24:26 server kernel: [979193.076399] BUG: unable to handle > kernel NULL pointer dereference at 0000000000000008 > Dec 28 16:24:26 server kernel: [979193.076401] IP: [<ffffffff8116952f>] > __blkdev_put+0x17f/0x1d0 > Dec 28 16:24:26 server kernel: [979193.076408] PGD 4bdcaa067 PUD > 4bdc43067 PMD 0 > Dec 28 16:24:26 server kernel: [979193.076410] Oops: 0000 [#1] SMP > Dec 28 16:24:26 server kernel: [979193.076412] CPU 6 > Dec 28 16:24:26 server kernel: [979193.076413] Modules linked in: bridge > stp llc nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables > raid1 md_mod dm_round_robin sd_mod crc_t10dif ib_srp scsi_transport_srp > scsi_tgt xt_ETHOIP6(O) x_tables vhost_net(O) macvtap macvlan tun(O) > nf_conntrack_ipv4 nf_conntrack nf_defrag_ipv4 rdma_ucm rdma_cm iw_cm > ib_addr ib_ipoib ib_cm ib_sa ib_uverbs ib_umad ib_qib mlx4_ib ib_mthca > ib_mad ib_core dm_multipath scsi_dh scsi_mod kvm_amd kvm powernow_k8 > mperf psmouse crc32c_intel microcode tpm_tis tpm tpm_bios serio_raw > evdev amd64_edac_mod edac_core edac_mce_amd i2c_piix4 button processor > thermal_sys mlx4_core > Dec 28 16:24:26 server kernel: [979193.076440] > Dec 28 16:24:26 server kernel: [979193.076442] Pid: 56544, comm: > multipath Tainted: G O 3.4.71-3-pserver #1 Supermicro BHQGE/BHQGE > Dec 28 16:24:26 server kernel: [979193.076445] RIP: > 0010:[<ffffffff8116952f>] [<ffffffff8116952f>] __blkdev_put+0x17f/0x1d0 > Dec 28 16:24:26 server kernel: [979193.076448] RSP: > 0018:ffff882802f4beb8 EFLAGS: 00010246 > Dec 28 16:24:26 server kernel: [979193.076449] RAX: 0000000000000000 > RBX: ffff881ff78b0d00 RCX: 0000000000000001 > Dec 28 16:24:26 server kernel: [979193.076451] RDX: 0000000000000000 > RSI: 000000000000001d RDI: ffff881ff78b0d18 > Dec 28 16:24:26 server kernel: [979193.076452] RBP: 0000000000000000 > R08: 0000000000000000 R09: 0000000000000000 > Dec 28 16:24:26 server kernel: [979193.076453] R10: 0000000000000000 > R11: 0000000000000246 R12: 000000000000001d > Dec 28 16:24:26 server kernel: [979193.076455] R13: ffff881ff78b0d18 > R14: ffff8807f9e7f400 R15: ffff8804a8d77710 > Dec 28 16:24:26 server kernel: [979193.076457] FS: > 00007ff8c80fe7a0(0000) GS:ffff880807d80000(0000) knlGS:0000000000000000 > Dec 28 16:24:26 server kernel: [979193.076458] CS: 0010 DS: 0000 ES: > 0000 CR0: 0000000080050033 > Dec 28 16:24:26 server kernel: [979193.076460] CR2: 0000000000000008 > CR3: 000000064765f000 CR4: 00000000000407e0 > Dec 28 16:24:26 server kernel: [979193.076461] DR0: 0000000000000000 > DR1: 0000000000000000 DR2: 0000000000000000 > Dec 28 16:24:26 server kernel: [979193.076463] DR3: 0000000000000000 > DR6: 00000000ffff0ff0 DR7: 0000000000000400 > Dec 28 16:24:26 server kernel: [979193.076464] Process multipath (pid: > 56544, threadinfo ffff882802f4a000, task ffff8828020106d0) > Dec 28 16:24:26 server kernel: [979193.076466] Stack: > Dec 28 16:24:26 server kernel: [979193.076466] 0000000000000000 > 0000000000000000 ffff880803cf2580 ffff8804a8d77700 > Dec 28 16:24:26 server kernel: [979193.076468] 0000000000000010 > ffff88100363eff0 ffff881004609b00 ffff882003c20020 > Dec 28 16:24:26 server kernel: [979193.076470] ffff8804a8d77710 > ffffffff81136bad 00007fffbdc8f420 ffff8804a8d77700 > Dec 28 16:24:26 server kernel: [979193.076472] Call Trace: > Dec 28 16:24:26 server kernel: [979193.076477] [<ffffffff81136bad>] ? > fput+0xdd/0x270 > Dec 28 16:24:26 server kernel: [979193.076479] [<ffffffff81132f0c>] ? > filp_close+0x5c/0x90 > Dec 28 16:24:26 server kernel: [979193.076481] [<ffffffff81132fb1>] ? > sys_close+0x71/0xc0 > Dec 28 16:24:26 server kernel: [979193.076484] [<ffffffff816801b9>] ? > system_call_fastpath+0x16/0x1b > Dec 28 16:24:26 server kernel: [979193.076486] Code: 8b 5c 24 18 48 8b > 6c 24 20 4c 8b 64 24 28 4c 8b 6c 24 30 4c 8b 74 24 38 4c 8b 7c 24 40 48 > 83 c4 48 c3 66 90 49 8b 86 48 03 00 00 <48> 8b 40 08 48 85 c0 0f 84 fc > fe ff ff 44 89 e6 4c 89 f7 ff d0 > Dec 28 16:24:26 server kernel: [979193.076500] RIP [<ffffffff8116952f>] > __blkdev_put+0x17f/0x1d0 > Dec 28 16:24:26 server kernel: [979193.076503] RSP <ffff882802f4beb8> > Dec 28 16:24:26 server kernel: [979193.076504] CR2: 0000000000000008 > Dec 28 16:24:26 server kernel: [979193.077599] ---[ end trace > 23f39da823d257f9 ]--- > > disassamble results show: > 1465 static int __blkdev_put(struct block_device *bdev, fmode_t mode, > int for_part) > 1466 { > 0xffffffff81162d10 <+0>: sub $0x48,%rsp > 0xffffffff81162d14 <+4>: mov %r13,0x30(%rsp) > 0xffffffff81162d1d <+13>: mov %rbx,0x18(%rsp) > 0xffffffff81162d22 <+18>: mov %rbp,0x20(%rsp) > 0xffffffff81162d27 <+23>: mov %r12,0x28(%rsp) > 0xffffffff81162d2c <+28>: mov %edx,%ebp > 0xffffffff81162d2e <+30>: mov %r14,0x38(%rsp) > 0xffffffff81162d33 <+35>: mov %r15,0x40(%rsp) > 0xffffffff81162d38 <+40>: mov %rdi,%rbx > 0xffffffff81162d45 <+53>: mov %esi,%r12d > > 1467 int ret = 0; > 0xffffffff81162d8e <+126>: xor %ebp,%ebp > > 1468 struct gendisk *disk = bdev->bd_disk; > 0xffffffff81162d3b <+43>: mov 0x90(%rdi),%r14 > > 1469 struct block_device *victim = NULL; > 1470 > 1471 mutex_lock_nested(&bdev->bd_mutex, for_part); > 0xffffffff81162d19 <+9>: lea 0x18(%rdi),%r13 > ---Type <return> to continue, or q <return> to quit--- > 0xffffffff81162d42 <+50>: mov %r13,%rdi > 0xffffffff81162d48 <+56>: callq 0xffffffff8166ece0 <mutex_lock> > > 1472 if (for_part) > 0xffffffff81162d4d <+61>: test %ebp,%ebp > 0xffffffff81162d4f <+63>: je 0xffffffff81162d57 <__blkdev_put+71> > > 1473 bdev->bd_part_count--; > 0xffffffff81162d51 <+65>: decl 0x88(%rbx) > > 1474 > 1475 if (!--bdev->bd_openers) { > 0xffffffff81162d57 <+71>: mov 0x4(%rbx),%eax > 0xffffffff81162d5a <+74>: dec %eax > 0xffffffff81162d5c <+76>: test %eax,%eax > 0xffffffff81162d5e <+78>: mov %eax,0x4(%rbx) > 0xffffffff81162d61 <+81>: jne 0xffffffff81162d8e <__blkdev_put+126> > > 1476 WARN_ON_ONCE(bdev->bd_holders); > 0xffffffff81162d63 <+83>: mov 0x58(%rbx),%edx > 0xffffffff81162d66 <+86>: test %edx,%edx > 0xffffffff81162d68 <+88>: jne 0xffffffff81162e9b <__blkdev_put+395> > 0xffffffff81162e9b <+395>: cmpb $0x1,0x936b1e(%rip) # > 0xffffffff81a999c0 <__warned.29603> > 0xffffffff81162ea2 <+402>: je 0xffffffff81162d6e <__blkdev_put+94> > 0xffffffff81162ea8 <+408>: mov $0x5c4,%esi > 0xffffffff81162ead <+413>: mov $0xffffffff8193f5a7,%rdi > 0xffffffff81162eb4 <+420>: callq 0xffffffff81036ee0 <warn_slowpath_null> > 0xffffffff81162eb9 <+425>: movb $0x1,0x936b00(%rip) # > 0xffffffff81a999c0 <__warned.29603> > 0xffffffff81162ec0 <+432>: jmpq 0xffffffff81162d6e <__blkdev_put+94> > 0xffffffff81162ec5: data32 nopw %cs:0x0(%rax,%rax,1) > > 1484 } > 1485 if (bdev->bd_contains == bdev) { > 0xffffffff81162d90 <+128>: cmp %rbx,0x70(%rbx) > 0xffffffff81162d94 <+132>: je 0xffffffff81162e78 <__blkdev_put+360> > > 1486 if (disk->fops->release) > ---Type <return> to continue, or q <return> to quit--- > 0xffffffff81162e78 <+360>: mov 0x348(%r14),%raxat > 0xffffffff81162e7f <+367>: mov 0x8(%rax),%rax > 0xffffffff81162e83 <+371>: test %rax,%rax > 0xffffffff81162e86 <+374>: je 0xffffffff81162d9a <__blkdev_put+138> > > 1487 ret = disk->fops->release(disk, mode); > 0xffffffff81162e8c <+380>: mov %r12d,%esi > 0xffffffff81162e8f <+383>: mov %r14,%rdi > 0xffffffff81162e92 <+386>: callq *%rax > 0xffffffff81162e94 <+388>: mov %eax,%ebp > 0xffffffff81162e96 <+390>: jmpq 0xffffffff81162d9a <__blkdev_put+138> > snip > > Bug happened at line 1486, looks disk->fops is NULL here for some > reason, is it reasonable to add a check like: > > if (disk->fops) > if (disk->fops->release) > ret = disk->fops->release(disk, mode); > > > Happy New Year and Best regards:) > Jack > Ping, could you share opnions on this, attached with patch I proposaled. Jack [-- Attachment #2: 0001-fix-null-pointer-dereference-in-__blkdev_put.patch --] [-- Type: text/x-patch, Size: 2575 bytes --] >From 153918f99e45c685700e919a92384395dc18fd5d Mon Sep 17 00:00:00 2001 From: Jack Wang <jinpu.wang@profitbricks.com> Date: Thu, 2 Jan 2014 10:24:29 +0100 Subject: [PATCH] fix null pointer dereference in __blkdev_put We were hit by bug below: Dec 28 16:24:26 pserver1812 kernel: [979193.076399] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 Dec 28 16:24:26 pserver1812 kernel: [979193.076401] IP: [<ffffffff8116952f>] __blkdev_put+0x17f/0x1d0 Dec 28 16:24:26 pserver1812 kernel: [979193.076442] Pid: 56544, comm: multipath Tainted: G O 3.4.71-3-pserver #1 Supermicro BHQGE/BHQGE Dec 28 16:24:26 pserver1812 kernel: [979193.076445] RIP: 0010:[<ffffffff8116952f>] [<ffffffff8116952f>] __blkdev_put+0x17f/0x1d0 Dec 28 16:24:26 pserver1812 kernel: [979193.076472] Call Trace: Dec 28 16:24:26 pserver1812 kernel: [979193.076477] [<ffffffff81136bad>] ? fput+0xdd/0x270 Dec 28 16:24:26 pserver1812 kernel: [979193.076479] [<ffffffff81132f0c>] ? filp_close+0x5c/0x90 Dec 28 16:24:26 pserver1812 kernel: [979193.076481] [<ffffffff81132fb1>] ? sys_close+0x71/0xc0 Dec 28 16:24:26 pserver1812 kernel: [979193.076484] [<ffffffff816801b9>] ? system_call_fastpath+0x16/0x1b Dec 28 16:24:26 pserver1812 kernel: [979193.076486] Code: 8b 5c 24 18 48 8b 6c 24 20 4c 8b 64 24 28 4c 8b 6c 24 30 4c 8b 74 24 38 4c 8b 7c 24 40 48 83 c4 48 c3 66 90 49 8b 86 48 03 00 00 <48> 8b 40 08 48 85 c0 0f 84 fc fe ff ff 44 89 e6 4c 89 f7 ff d0 Dec 28 16:24:26 pserver1812 kernel: [979193.076500] RIP [<ffffffff8116952f>] __blkdev_put+0x17f/0x1d0 Dec 28 16:24:26 pserver1812 kernel: [979193.076503] RSP <ffff882802f4beb8> Dec 28 16:24:26 pserver1812 kernel: [979193.076504] CR2: 0000000000000008 Dec 28 16:24:26 pserver1812 kernel: [979193.077599] ---[ end trace 23f39da823d257f9 ]--- Disamble code show null pointer happened in fops, fix by check before use it. Signed-off-by: Jack Wang <jinpu.wang@profitbricks.com> --- fs/block_dev.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/fs/block_dev.c b/fs/block_dev.c index 319d9c7..d3c45b4 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -1483,8 +1483,9 @@ static int __blkdev_put(struct block_device *bdev, fmode_t mode, int for_part) &default_backing_dev_info); } if (bdev->bd_contains == bdev) { - if (disk->fops->release) - ret = disk->fops->release(disk, mode); + if (disk->fops) + if (disk->fops->release) + ret = disk->fops->release(disk, mode); } if (!bdev->bd_openers) { struct module *owner = disk->fops->owner; -- 1.8.4 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [BUG]NULL pointer dereference at 0000000000000008 __blkdev_put+0x17f/0x1d0 2014-01-02 9:36 ` Jack Wang @ 2014-01-04 6:09 ` Al Viro 2014-01-06 8:45 ` Jack Wang 0 siblings, 1 reply; 4+ messages in thread From: Al Viro @ 2014-01-04 6:09 UTC (permalink / raw) To: Jack Wang; +Cc: linux-fsdevel, linux-kernel@vger.kernel.org, Jens Axboe On Thu, Jan 02, 2014 at 10:36:30AM +0100, Jack Wang wrote: > > Bug happened at line 1486, looks disk->fops is NULL here for some > > reason, is it reasonable to add a check like: > > > > if (disk->fops) > > if (disk->fops->release) > > ret = disk->fops->release(disk, mode); > > > > > > Happy New Year and Best regards:) > > Jack > > > > Ping, could you share opnions on this, attached with patch I proposaled. Sorry, had been sick since mid-December ;-/ The patch is not a good idea - in the best case it's papering over a bug (and insufficiently so, at that, since there are other places where disk->fops->some_method is checked). gendisk->fops should never be assigned NULL; it starts life with NULL ->fops, but that should be assigned a non-NULL value (and never modified afterwards) before anyone can see it. Moreover, even if some driver has fscked up and forgot to initialize the damn thing, get_gendisk() would've refused to return such a thing to any callers (including __blkdev_get()). Note that __blkdev_get() would oops on such a thing if get_gendisk() somehow returned it. Looks like something is shitting over bdev->bd_disk or bdev->bd_disk->fops. The offsets in the disassembled code are all wrong (including that from beginning of function to oopsing instruction), but the code match is good, so I agree that we are hitting bdev->bd_disk->fops == NULL here. The question is how it has happened - that's where the real bug is... How reproducible it is? And which kernel, while we are at it? This area didn't get a lot of changes lately, but still... ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [BUG]NULL pointer dereference at 0000000000000008 __blkdev_put+0x17f/0x1d0 2014-01-04 6:09 ` Al Viro @ 2014-01-06 8:45 ` Jack Wang 0 siblings, 0 replies; 4+ messages in thread From: Jack Wang @ 2014-01-06 8:45 UTC (permalink / raw) To: Al Viro; +Cc: linux-fsdevel, linux-kernel@vger.kernel.org, Jens Axboe On 01/04/2014 07:09 AM, Al Viro wrote: > On Thu, Jan 02, 2014 at 10:36:30AM +0100, Jack Wang wrote: > >>> Bug happened at line 1486, looks disk->fops is NULL here for some >>> reason, is it reasonable to add a check like: >>> >>> if (disk->fops) >>> if (disk->fops->release) >>> ret = disk->fops->release(disk, mode); >>> >>> >>> Happy New Year and Best regards:) >>> Jack >>> >> >> Ping, could you share opnions on this, attached with patch I proposaled. > > Sorry, had been sick since mid-December ;-/ The patch is not a good idea - > in the best case it's papering over a bug (and insufficiently so, at that, > since there are other places where disk->fops->some_method is checked). > > gendisk->fops should never be assigned NULL; it starts life with NULL > ->fops, but that should be assigned a non-NULL value (and never modified > afterwards) before anyone can see it. Moreover, even if some driver has > fscked up and forgot to initialize the damn thing, get_gendisk() would've > refused to return such a thing to any callers (including __blkdev_get()). > Note that __blkdev_get() would oops on such a thing if get_gendisk() > somehow returned it. > > Looks like something is shitting over bdev->bd_disk or bdev->bd_disk->fops. > The offsets in the disassembled code are all wrong (including that from > beginning of function to oopsing instruction), but the code match is good, > so I agree that we are hitting bdev->bd_disk->fops == NULL here. The > question is how it has happened - that's where the real bug is... > > How reproducible it is? And which kernel, while we are at it? This area > didn't get a lot of changes lately, but still... > Thanks Al for reply, and look into this. We're using 3.4.71, and this happened in production, we can not reproduce it yet. What I could see is: before this happened, we saw scsi devices offlined, and multipath failed path, raid1 failed member device. Possible the bug lies in drivers md-raid1, dm-multipath or sd? How could I narrow it down? Could you teach me? Thanks, wish you happy and healthy! Jack ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2014-01-06 8:45 UTC | newest] Thread overview: 4+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2013-12-30 15:55 [BUG]NULL pointer dereference at 0000000000000008 __blkdev_put+0x17f/0x1d0 Jack Wang 2014-01-02 9:36 ` Jack Wang 2014-01-04 6:09 ` Al Viro 2014-01-06 8:45 ` Jack Wang
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