Re: [PATCH V3] scsi_debugfs: fix crash in scsi_show_rq()

2017-11-08 Thread Ming Lei 
On Wed, Nov 08, 2017 at 08:01:08AM -0800, James Bottomley wrote:
> On Wed, 2017-11-08 at 21:21 +0800, Ming Lei wrote:
> > cmd->cmnd can be allocated/freed dynamically in case of
> > T10_PI_TYPE2_PROTECTION,
> > so we should check it in scsi_show_rq() because this request may have
> > been freed in scsi_show_rq().
> > 
> > This patch fixs the following kernel crash when dumping request via
> > block's
> > debugfs interface:
> > 
> > [  252.962045] BUG: unable to handle kernel NULL pointer dereference
> > at   (null)
> > [  252.963007] IP: scsi_format_opcode_name+0x1a/0x1c0
> > [  252.963007] PGD 25e75a067 P4D 25e75a067 PUD 25e75b067 PMD 0
> > [  252.963007] Oops:  [#1] PREEMPT SMP
> > [  252.963007] Dumping ftrace buffer:
> > [  252.963007](ftrace buffer empty)
> > [  252.963007] Modules linked in: scsi_debug ebtable_filter ebtables
> > ip6table_filter ip6_tables xt_CHECKSUM iptable_mangle ipt_MASQUERADE
> > nf_nat_masquerade_ipv4 iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4
> > nf_nat_ipv4 nf_nat nf_conntrack libcrc32c bridge stp llc
> > iptable_filter fuse ip_tables sd_mod sg mptsas mptscsih mptbase
> > crc32c_intel ahci libahci nvme serio_raw scsi_transport_sas libata
> > lpc_ich nvme_core virtio_scsi binfmt_misc dm_mod iscsi_tcp
> > libiscsi_tcp libiscsi scsi_transport_iscsi null_blk configs
> > [  252.963007] CPU: 1 PID: 1881 Comm: cat Not tainted 4.14.0-
> > rc2.blk_mq_io_hang+ #516
> > [  252.963007] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
> > BIOS 1.9.3-1.fc25 04/01/2014
> > [  252.963007] task: 88025e6f6000 task.stack: c90001bd
> > [  252.963007] RIP: 0010:scsi_format_opcode_name+0x1a/0x1c0
> > [  252.963007] RSP: 0018:c90001bd3c50 EFLAGS: 00010286
> > [  252.963007] RAX: 4843 RBX: 0050 RCX:
> > 
> > [  252.963007] RDX:  RSI: 0050 RDI:
> > c90001bd3cd8
> > [  252.963007] RBP: c90001bd3c88 R08: 1000 R09:
> > 
> > [  252.963007] R10: 880275134000 R11: 88027513406c R12:
> > 0050
> > [  252.963007] R13: c90001bd3cd8 R14:  R15:
> > 
> > [  252.963007] FS:  7f4d11762700() GS:88027fc4()
> > knlGS:
> > [  252.963007] CS:  0010 DS:  ES:  CR0: 80050033
> > [  252.963007] CR2:  CR3: 00025e789003 CR4:
> > 003606e0
> > [  252.963007] DR0:  DR1:  DR2:
> > 
> > [  252.963007] DR3:  DR6: fffe0ff0 DR7:
> > 0400
> > [  252.963007] Call Trace:
> > [  252.963007]  __scsi_format_command+0x27/0xc0
> > [  252.963007]  scsi_show_rq+0x5c/0xc0
> > [  252.963007]  ? seq_printf+0x4e/0x70
> > [  252.963007]  ? blk_flags_show+0x5b/0xf0
> > [  252.963007]  __blk_mq_debugfs_rq_show+0x116/0x130
> > [  252.963007]  blk_mq_debugfs_rq_show+0xe/0x10
> > [  252.963007]  seq_read+0xfe/0x3b0
> > [  252.963007]  ? __handle_mm_fault+0x631/0x1150
> > [  252.963007]  full_proxy_read+0x54/0x90
> > [  252.963007]  __vfs_read+0x37/0x160
> > [  252.963007]  ? security_file_permission+0x9b/0xc0
> > [  252.963007]  vfs_read+0x96/0x130
> > [  252.963007]  SyS_read+0x55/0xc0
> > [  252.963007]  entry_SYSCALL_64_fastpath+0x1a/0xa5
> > [  252.963007] RIP: 0033:0x7f4d1127e9b0
> > [  252.963007] RSP: 002b:7ffd27082568 EFLAGS: 0246 ORIG_RAX:
> > 
> > [  252.963007] RAX: ffda RBX: 7f4d1154bb20 RCX:
> > 7f4d1127e9b0
> > [  252.963007] RDX: 0002 RSI: 7f4d115a7000 RDI:
> > 0003
> > [  252.963007] RBP: 00021010 R08:  R09:
> > 
> > [  252.963007] R10: 037b R11: 0246 R12:
> > 00022000
> > [  252.963007] R13: 7f4d1154bb78 R14: 1000 R15:
> > 0002
> > [  252.963007] Code: c6 e8 1b ca 24 00 eb 8c e8 74 2c ae ff 0f 1f 40
> > 00 0f 1f 44 00 00 55 48 89 e5 41 56 41 55 41 54 53 49 89 fd 49 89 f4
> > 48 83 ec 18 <44> 0f b6 32 48 c7 45 c8 00 00 00 00 65 48 8b 04 25 28
> > 00 00 00
> > [  252.963007] RIP: scsi_format_opcode_name+0x1a/0x1c0 RSP:
> > c90001bd3c50
> > [  252.963007] CR2: 
> > [  252.963007] ---[ end trace 83c5bddfbaa6573c ]---
> > [  252.963007] Kernel panic - not syncing: Fatal exception
> > [  252.963007] Dumping ftrace buffer:
> > [  252.963007](ftrace buffer empty)
> > [  252.963007] Kernel Offset: disabled
> > [  252.963007] ---[ end Kernel panic - not syncing: Fatal exception
> > 
> > Fixes: 0eebd005dd07(scsi: Implement blk_mq_ops.show_rq())
> > Cc: Bart Van Assche 
> > Cc: Omar Sandoval 
> > Cc: Martin K. Petersen 
> > Cc: James Bottomley 
> > Cc: Hannes Reinecke 
> > Signed-off-by: Ming Lei 
> > ---
> > V2:
> > - fix typo
> > V3:
> > - prefer

Re: [PATCH V3] scsi_debugfs: fix crash in scsi_show_rq()

2017-11-08 Thread James Bottomley 
On Wed, 2017-11-08 at 21:21 +0800, Ming Lei wrote:
> cmd->cmnd can be allocated/freed dynamically in case of
> T10_PI_TYPE2_PROTECTION,
> so we should check it in scsi_show_rq() because this request may have
> been freed in scsi_show_rq().
> 
> This patch fixs the following kernel crash when dumping request via
> block's
> debugfs interface:
> 
> [  252.962045] BUG: unable to handle kernel NULL pointer dereference
> at   (null)
> [  252.963007] IP: scsi_format_opcode_name+0x1a/0x1c0
> [  252.963007] PGD 25e75a067 P4D 25e75a067 PUD 25e75b067 PMD 0
> [  252.963007] Oops:  [#1] PREEMPT SMP
> [  252.963007] Dumping ftrace buffer:
> [  252.963007](ftrace buffer empty)
> [  252.963007] Modules linked in: scsi_debug ebtable_filter ebtables
> ip6table_filter ip6_tables xt_CHECKSUM iptable_mangle ipt_MASQUERADE
> nf_nat_masquerade_ipv4 iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4
> nf_nat_ipv4 nf_nat nf_conntrack libcrc32c bridge stp llc
> iptable_filter fuse ip_tables sd_mod sg mptsas mptscsih mptbase
> crc32c_intel ahci libahci nvme serio_raw scsi_transport_sas libata
> lpc_ich nvme_core virtio_scsi binfmt_misc dm_mod iscsi_tcp
> libiscsi_tcp libiscsi scsi_transport_iscsi null_blk configs
> [  252.963007] CPU: 1 PID: 1881 Comm: cat Not tainted 4.14.0-
> rc2.blk_mq_io_hang+ #516
> [  252.963007] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
> BIOS 1.9.3-1.fc25 04/01/2014
> [  252.963007] task: 88025e6f6000 task.stack: c90001bd
> [  252.963007] RIP: 0010:scsi_format_opcode_name+0x1a/0x1c0
> [  252.963007] RSP: 0018:c90001bd3c50 EFLAGS: 00010286
> [  252.963007] RAX: 4843 RBX: 0050 RCX:
> 
> [  252.963007] RDX:  RSI: 0050 RDI:
> c90001bd3cd8
> [  252.963007] RBP: c90001bd3c88 R08: 1000 R09:
> 
> [  252.963007] R10: 880275134000 R11: 88027513406c R12:
> 0050
> [  252.963007] R13: c90001bd3cd8 R14:  R15:
> 
> [  252.963007] FS:  7f4d11762700() GS:88027fc4()
> knlGS:
> [  252.963007] CS:  0010 DS:  ES:  CR0: 80050033
> [  252.963007] CR2:  CR3: 00025e789003 CR4:
> 003606e0
> [  252.963007] DR0:  DR1:  DR2:
> 
> [  252.963007] DR3:  DR6: fffe0ff0 DR7:
> 0400
> [  252.963007] Call Trace:
> [  252.963007]  __scsi_format_command+0x27/0xc0
> [  252.963007]  scsi_show_rq+0x5c/0xc0
> [  252.963007]  ? seq_printf+0x4e/0x70
> [  252.963007]  ? blk_flags_show+0x5b/0xf0
> [  252.963007]  __blk_mq_debugfs_rq_show+0x116/0x130
> [  252.963007]  blk_mq_debugfs_rq_show+0xe/0x10
> [  252.963007]  seq_read+0xfe/0x3b0
> [  252.963007]  ? __handle_mm_fault+0x631/0x1150
> [  252.963007]  full_proxy_read+0x54/0x90
> [  252.963007]  __vfs_read+0x37/0x160
> [  252.963007]  ? security_file_permission+0x9b/0xc0
> [  252.963007]  vfs_read+0x96/0x130
> [  252.963007]  SyS_read+0x55/0xc0
> [  252.963007]  entry_SYSCALL_64_fastpath+0x1a/0xa5
> [  252.963007] RIP: 0033:0x7f4d1127e9b0
> [  252.963007] RSP: 002b:7ffd27082568 EFLAGS: 0246 ORIG_RAX:
> 
> [  252.963007] RAX: ffda RBX: 7f4d1154bb20 RCX:
> 7f4d1127e9b0
> [  252.963007] RDX: 0002 RSI: 7f4d115a7000 RDI:
> 0003
> [  252.963007] RBP: 00021010 R08:  R09:
> 
> [  252.963007] R10: 037b R11: 0246 R12:
> 00022000
> [  252.963007] R13: 7f4d1154bb78 R14: 1000 R15:
> 0002
> [  252.963007] Code: c6 e8 1b ca 24 00 eb 8c e8 74 2c ae ff 0f 1f 40
> 00 0f 1f 44 00 00 55 48 89 e5 41 56 41 55 41 54 53 49 89 fd 49 89 f4
> 48 83 ec 18 <44> 0f b6 32 48 c7 45 c8 00 00 00 00 65 48 8b 04 25 28
> 00 00 00
> [  252.963007] RIP: scsi_format_opcode_name+0x1a/0x1c0 RSP:
> c90001bd3c50
> [  252.963007] CR2: 
> [  252.963007] ---[ end trace 83c5bddfbaa6573c ]---
> [  252.963007] Kernel panic - not syncing: Fatal exception
> [  252.963007] Dumping ftrace buffer:
> [  252.963007](ftrace buffer empty)
> [  252.963007] Kernel Offset: disabled
> [  252.963007] ---[ end Kernel panic - not syncing: Fatal exception
> 
> Fixes: 0eebd005dd07(scsi: Implement blk_mq_ops.show_rq())
> Cc: Bart Van Assche 
> Cc: Omar Sandoval 
> Cc: Martin K. Petersen 
> Cc: James Bottomley 
> Cc: Hannes Reinecke 
> Signed-off-by: Ming Lei 
> ---
> V2:
>   - fix typo
> V3:
>   - prefer to dump data and accept read-after-free
>   - add some comment
> 
> James, since read-after-free is inevitable and we prefer to dump
> data,
> we needn't to move clearing the buffer pointer before freeing the
> buffer
> in sd_uninit_command(), otherwise we may miss

[PATCH V3] scsi_debugfs: fix crash in scsi_show_rq()

2017-11-08 Thread Ming Lei 
cmd->cmnd can be allocated/freed dynamically in case of T10_PI_TYPE2_PROTECTION,
so we should check it in scsi_show_rq() because this request may have
been freed in scsi_show_rq().

This patch fixs the following kernel crash when dumping request via block's
debugfs interface:

[  252.962045] BUG: unable to handle kernel NULL pointer dereference at 
  (null)
[  252.963007] IP: scsi_format_opcode_name+0x1a/0x1c0
[  252.963007] PGD 25e75a067 P4D 25e75a067 PUD 25e75b067 PMD 0
[  252.963007] Oops:  [#1] PREEMPT SMP
[  252.963007] Dumping ftrace buffer:
[  252.963007](ftrace buffer empty)
[  252.963007] Modules linked in: scsi_debug ebtable_filter ebtables 
ip6table_filter ip6_tables xt_CHECKSUM iptable_mangle ipt_MASQUERADE 
nf_nat_masquerade_ipv4 iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 
nf_nat nf_conntrack libcrc32c bridge stp llc iptable_filter fuse ip_tables 
sd_mod sg mptsas mptscsih mptbase crc32c_intel ahci libahci nvme serio_raw 
scsi_transport_sas libata lpc_ich nvme_core virtio_scsi binfmt_misc dm_mod 
iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi null_blk configs
[  252.963007] CPU: 1 PID: 1881 Comm: cat Not tainted 
4.14.0-rc2.blk_mq_io_hang+ #516
[  252.963007] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 
1.9.3-1.fc25 04/01/2014
[  252.963007] task: 88025e6f6000 task.stack: c90001bd
[  252.963007] RIP: 0010:scsi_format_opcode_name+0x1a/0x1c0
[  252.963007] RSP: 0018:c90001bd3c50 EFLAGS: 00010286
[  252.963007] RAX: 4843 RBX: 0050 RCX: 
[  252.963007] RDX:  RSI: 0050 RDI: c90001bd3cd8
[  252.963007] RBP: c90001bd3c88 R08: 1000 R09: 
[  252.963007] R10: 880275134000 R11: 88027513406c R12: 0050
[  252.963007] R13: c90001bd3cd8 R14:  R15: 
[  252.963007] FS:  7f4d11762700() GS:88027fc4() 
knlGS:
[  252.963007] CS:  0010 DS:  ES:  CR0: 80050033
[  252.963007] CR2:  CR3: 00025e789003 CR4: 003606e0
[  252.963007] DR0:  DR1:  DR2: 
[  252.963007] DR3:  DR6: fffe0ff0 DR7: 0400
[  252.963007] Call Trace:
[  252.963007]  __scsi_format_command+0x27/0xc0
[  252.963007]  scsi_show_rq+0x5c/0xc0
[  252.963007]  ? seq_printf+0x4e/0x70
[  252.963007]  ? blk_flags_show+0x5b/0xf0
[  252.963007]  __blk_mq_debugfs_rq_show+0x116/0x130
[  252.963007]  blk_mq_debugfs_rq_show+0xe/0x10
[  252.963007]  seq_read+0xfe/0x3b0
[  252.963007]  ? __handle_mm_fault+0x631/0x1150
[  252.963007]  full_proxy_read+0x54/0x90
[  252.963007]  __vfs_read+0x37/0x160
[  252.963007]  ? security_file_permission+0x9b/0xc0
[  252.963007]  vfs_read+0x96/0x130
[  252.963007]  SyS_read+0x55/0xc0
[  252.963007]  entry_SYSCALL_64_fastpath+0x1a/0xa5
[  252.963007] RIP: 0033:0x7f4d1127e9b0
[  252.963007] RSP: 002b:7ffd27082568 EFLAGS: 0246 ORIG_RAX: 

[  252.963007] RAX: ffda RBX: 7f4d1154bb20 RCX: 7f4d1127e9b0
[  252.963007] RDX: 0002 RSI: 7f4d115a7000 RDI: 0003
[  252.963007] RBP: 00021010 R08:  R09: 
[  252.963007] R10: 037b R11: 0246 R12: 00022000
[  252.963007] R13: 7f4d1154bb78 R14: 1000 R15: 0002
[  252.963007] Code: c6 e8 1b ca 24 00 eb 8c e8 74 2c ae ff 0f 1f 40 00 0f 1f 
44 00 00 55 48 89 e5 41 56 41 55 41 54 53 49 89 fd 49 89 f4 48 83 ec 18 <44> 0f 
b6 32 48 c7 45 c8 00 00 00 00 65 48 8b 04 25 28 00 00 00
[  252.963007] RIP: scsi_format_opcode_name+0x1a/0x1c0 RSP: c90001bd3c50
[  252.963007] CR2: 
[  252.963007] ---[ end trace 83c5bddfbaa6573c ]---
[  252.963007] Kernel panic - not syncing: Fatal exception
[  252.963007] Dumping ftrace buffer:
[  252.963007](ftrace buffer empty)
[  252.963007] Kernel Offset: disabled
[  252.963007] ---[ end Kernel panic - not syncing: Fatal exception

Fixes: 0eebd005dd07(scsi: Implement blk_mq_ops.show_rq())
Cc: Bart Van Assche 
Cc: Omar Sandoval 
Cc: Martin K. Petersen 
Cc: James Bottomley 
Cc: Hannes Reinecke 
Signed-off-by: Ming Lei 
---
V2:
- fix typo
V3:
- prefer to dump data and accept read-after-free
- add some comment

James, since read-after-free is inevitable and we prefer to dump data,
we needn't to move clearing the buffer pointer before freeing the buffer
in sd_uninit_command(), otherwise we may miss the dump a bit

 drivers/scsi/scsi_debugfs.c | 12 +++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_debugfs.c b/drivers/scsi/scsi_debugfs.c
index 5e9755008aed..2320d8f569b8 100644
--- a/drivers/scsi/scsi_debugfs.c