Re: [PATCH] scsi: sr: fix oob access in get_capabilities

[Kefeng Wang]

On 2017/3/20 22:29, Martin K. Petersen wrote:
> Kefeng Wang  writes:
> 
> Kefeng,
> 
>> The issue still exists, the patch return zero in scsi_mode_sense(), but zero 
>> means
>> SAM_STAT_GOOD in scsi_status_is_good(), so n will be still bigger than 512;
> 
> OK, I checked the other users of scsi_mode_sense(). So let's keep this
> fix local to sr.c for now.
> 
> How about the following?
> 
> 
> scsi: sr: Sanity check returned mode data
> 
> Kefeng Wang discovered that old versions of the QEMU CD driver would
> return mangled mode data causing us to walk off the end of the buffer in
> an attempt to parse it. Sanity check the returned mode sense data.
> 
> Cc: 
> Reported-by: Kefeng Wang 
> Signed-off-by: Martin K. Petersen 
> 
> diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
> index 0b29b9329b1c..a8f630213a1a 100644
> --- a/drivers/scsi/sr.c
> +++ b/drivers/scsi/sr.c
> @@ -836,6 +836,7 @@ static void get_capabilities(struct scsi_cd *cd)
>   unsigned char *buffer;
>   struct scsi_mode_data data;
>   struct scsi_sense_hdr sshdr;
> + unsigned int ms_len = 128;
>   int rc, n;
>  
>   static const char *loadmech[] =
> @@ -862,10 +863,11 @@ static void get_capabilities(struct scsi_cd *cd)
>   scsi_test_unit_ready(cd->device, SR_TIMEOUT, MAX_RETRIES, );
>  
>   /* ask for mode page 0x2a */
> - rc = scsi_mode_sense(cd->device, 0, 0x2a, buffer, 128,
> + rc = scsi_mode_sense(cd->device, 0, 0x2a, buffer, ms_len,
>SR_TIMEOUT, 3, , NULL);
>  

move n = data.header_length + data.block_descriptor_length; here,

> - if (!scsi_status_is_good(rc)) {
> + if (!scsi_status_is_good(rc) || data.length > ms_len ||
> + data.header_length + data.block_descriptor_length > data.length) {

n > data.length

Tested-by: Kefeng Wang 

Thanks,
Kefeng

>   /* failed, drive doesn't have capabilities mode page */
>   cd->cdi.speed = 1;
>   cd->cdi.mask |= (CDC_CD_R | CDC_CD_RW | CDC_DVD_R |
> 
> 
> 
> .
> 

Re: [PATCH] scsi: sr: fix oob access in get_capabilities

[Martin K. Petersen]

Kefeng Wang  writes:

Kefeng,

> The issue still exists, the patch return zero in scsi_mode_sense(), but zero 
> means
> SAM_STAT_GOOD in scsi_status_is_good(), so n will be still bigger than 512;

OK, I checked the other users of scsi_mode_sense(). So let's keep this
fix local to sr.c for now.

How about the following?


scsi: sr: Sanity check returned mode data

Kefeng Wang discovered that old versions of the QEMU CD driver would
return mangled mode data causing us to walk off the end of the buffer in
an attempt to parse it. Sanity check the returned mode sense data.

Cc: 
Reported-by: Kefeng Wang 
Signed-off-by: Martin K. Petersen 

diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
index 0b29b9329b1c..a8f630213a1a 100644
--- a/drivers/scsi/sr.c
+++ b/drivers/scsi/sr.c
@@ -836,6 +836,7 @@ static void get_capabilities(struct scsi_cd *cd)
unsigned char *buffer;
struct scsi_mode_data data;
struct scsi_sense_hdr sshdr;
+   unsigned int ms_len = 128;
int rc, n;
 
static const char *loadmech[] =
@@ -862,10 +863,11 @@ static void get_capabilities(struct scsi_cd *cd)
scsi_test_unit_ready(cd->device, SR_TIMEOUT, MAX_RETRIES, );
 
/* ask for mode page 0x2a */
-   rc = scsi_mode_sense(cd->device, 0, 0x2a, buffer, 128,
+   rc = scsi_mode_sense(cd->device, 0, 0x2a, buffer, ms_len,
 SR_TIMEOUT, 3, , NULL);
 
-   if (!scsi_status_is_good(rc)) {
+   if (!scsi_status_is_good(rc) || data.length > ms_len ||
+   data.header_length + data.block_descriptor_length > data.length) {
/* failed, drive doesn't have capabilities mode page */
cd->cdi.speed = 1;
cd->cdi.mask |= (CDC_CD_R | CDC_CD_RW | CDC_DVD_R |

Re: [PATCH] scsi: sr: fix oob access in get_capabilities

[Kefeng Wang]

On 2017/3/18 7:29, Martin K. Petersen wrote:
> Kefeng Wang  writes:
> 
> Kefeng,
> 
>> root@localhost ~]# sg_modes -p 0x2a /dev/sr0
>> QEMU  QEMU DVD-ROM  0.15   peripheral_type: cd/dvd [0x5]
>> Mode parameter header from MODE SENSE(10):
>> Invalid block descriptor length=512, ignore
>>   Mode data length=36, medium type=0x70, specific param=0x00, longlba=0
>>   Block descriptor length=0
 MM capabilities and mechanical status (obsolete), page_control: current
>>  00 2a 12 00 00 71 60 29 00  02 c2 00 02 02 00 02 c2
>>  10 00 00 00 00
>> Unexpectedly received extra mode page responses, ignore
> 
> That looks pretty broken.
> 
> Could you try the following patch?

The issue still exists, the patch return zero in scsi_mode_sense(), but zero 
means
SAM_STAT_GOOD in scsi_status_is_good(), so n will be still bigger than 512;

Thanks,

Re: [PATCH] scsi: sr: fix oob access in get_capabilities

[Martin K. Petersen]

Kefeng Wang  writes:

Kefeng,

> root@localhost ~]# sg_modes -p 0x2a /dev/sr0
> QEMU  QEMU DVD-ROM  0.15   peripheral_type: cd/dvd [0x5]
> Mode parameter header from MODE SENSE(10):
> Invalid block descriptor length=512, ignore
>   Mode data length=36, medium type=0x70, specific param=0x00, longlba=0
>   Block descriptor length=0
>>> MM capabilities and mechanical status (obsolete), page_control: current
>  00 2a 12 00 00 71 60 29 00  02 c2 00 02 02 00 02 c2
>  10 00 00 00 00
> Unexpectedly received extra mode page responses, ignore

That looks pretty broken.

Could you try the following patch?

Thanks!

-- 
Martin K. Petersen  Oracle Linux Engineering

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index f41e6b84a1bd..51a4ce094450 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2485,6 +2485,10 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int 
modepage,
goto retry;
}
 
+   if (data->length > len ||
+   data->header_length + data->block_descriptor_length > data->length)
+   return 0;
+
return result;
 }
 EXPORT_SYMBOL(scsi_mode_sense);

Re: [PATCH] scsi: sr: fix oob access in get_capabilities

[Kefeng Wang]

On 2017/3/16 8:07, Martin K. Petersen wrote:
> Kefeng Wang  writes:
> 
> Kefeng,
> 
>> 'n = header_length + block_descriptor_length' could be greater than 512,
>> and will lead to oob access, so enlarge transfer buffer to fix it.
> 
> Can you share the output of sg_modes -p 0x2a /dev/srN for the offending
> drive?


root@localhost ~]# sg_modes -p 0x2a /dev/sr0
QEMU  QEMU DVD-ROM  0.15   peripheral_type: cd/dvd [0x5]
Mode parameter header from MODE SENSE(10):
Invalid block descriptor length=512, ignore
  Mode data length=36, medium type=0x70, specific param=0x00, longlba=0
  Block descriptor length=0
>> MM capabilities and mechanical status (obsolete), page_control: current
 00 2a 12 00 00 71 60 29 00  02 c2 00 02 02 00 02 c2
 10 00 00 00 00
Unexpectedly received extra mode page responses, ignore

note: the issue was found in guestos?  maybe some bugs exist in qemu?

Kefeng

> 
> This mode page is usually much smaller than 512 bytes (typically between
> 32 and 128 bytes).
> 

Re: [PATCH] scsi: sr: fix oob access in get_capabilities

[Martin K. Petersen]

Kefeng Wang  writes:

Kefeng,

> 'n = header_length + block_descriptor_length' could be greater than 512,
> and will lead to oob access, so enlarge transfer buffer to fix it.

Can you share the output of sg_modes -p 0x2a /dev/srN for the offending
drive?

This mode page is usually much smaller than 512 bytes (typically between
32 and 128 bytes).

-- 
Martin K. Petersen  Oracle Linux Engineering

Re: [PATCH] scsi: sr: fix oob access in get_capabilities

[Kefeng Wang]

Hi all，

On 2017/3/3 18:17, Kefeng Wang wrote:
> 'n = header_length + block_descriptor_length' could be greater than 512,
> and will lead to oob access, so enlarge transfer buffer to fix it.

I am not familiar with scsi protocol，so the patch may be wrong.
Question, is it reasonable for block_descriptor_length = 512 when mode page = 
0x2a?

The value shown below，

[4.516108] get_capabilities, n = 520, head_len = 8, blk_des_len = 512

> 
> ===
> BUG: KASAN: slab-out-of-bounds in sr_probe+0x570/0xcc0 at addr 
> 8809020e
> Read of size 1 by task kworker/u48:2/188
and the kasan print,

[4.516111] 
==
[4.516122] BUG: KASAN: slab-out-of-bounds in sr_probe+0x4a3/0xdc0 at addr 
88090210
[4.516125] Read of size 1 by task kworker/u48:3/677
[4.516131] CPU: 18 PID: 677 Comm: kworker/u48:3 Not tainted 4.10.0+ #9
[4.516133] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
[4.516143] Workqueue: events_unbound async_run_entry_fn
[4.516146] Call Trace:
[4.516156]  dump_stack+0x99/0xe4
[4.516162]  ? _atomic_dec_and_lock+0x12c/0x12c
[4.516166]  ? sr_probe+0x4a3/0xdc0
[4.516172]  kasan_object_err+0x1c/0x80
[4.516175]  kasan_report.part.0+0x2e4/0x830
[4.516182]  ? vprintk_default+0x1a/0x20
[4.516187]  ? printk+0x94/0xb0
[4.516190]  ? sr_probe+0x4a3/0xdc0
[4.516193]  kasan_report+0x44/0x70
[4.516197]  __asan_load1+0x47/0x50
[4.516199]  sr_probe+0x4a3/0xdc0
[4.516204]  ? __kernfs_new_node+0x142/0x1c0
[4.516207]  ? kernfs_next_descendant_post+0x84/0xe0
[4.516211]  ? kernfs_activate+0xa7/0x150
[4.516213]  ? sr_block_ioctl+0x130/0x130
[4.516218]  ? sysfs_do_create_link_sd+0xdd/0x160
[4.516224]  ? devices_kset_move_last+0x16a/0x220
[4.516227]  ? device_remove_groups+0x10/0x10
[4.516232]  ? mutex_lock+0xd/0x30
[4.516236]  ? device_links_check_suppliers+0x123/0x220
[4.516240]  ? driver_sysfs_add+0xf9/0x1b0
[4.516244]  driver_probe_device+0x1bf/0x4f0
[4.516249]  __device_attach_driver+0xf8/0x1b0
[4.516253]  ? __driver_attach+0x120/0x120
[4.516256]  bus_for_each_drv+0xfe/0x190
[4.516260]  ? bus_rescan_devices+0x20/0x20
[4.516263]  __device_attach+0x16e/0x200
[4.516267]  ? device_bind_driver+0x90/0x90
[4.516271]  ? kobject_uevent_env+0x1ae/0x890
[4.516275]  device_initial_probe+0xe/0x10
[4.516278]  bus_probe_device+0x124/0x190
[4.516282]  device_add+0x883/0xb10
[4.516285]  ? device_private_init+0x160/0x160
[4.516289]  ? __pm_runtime_resume+0x4d/0xa0
[4.516294]  scsi_sysfs_add_sdev+0xdb/0x450
[4.516300]  scsi_probe_and_add_lun+0x13da/0x1630
[4.516305]  ? scsi_free_host_dev+0x90/0x90
[4.516308]  ? rpm_check_suspend_allowed+0x170/0x170
[4.516313]  ? _raw_spin_unlock_bh+0xb0/0xb0
[4.516316]  ? rpm_check_suspend_allowed+0x9c/0x170
[4.516319]  ? __pm_runtime_resume+0x4d/0xa0
[4.516323]  __scsi_add_device+0x1a1/0x1c0
[4.516327]  ? scsi_target_reap+0x60/0x60
[4.516332]  ? async_synchronize_cookie_domain+0xbe/0x1a0
[4.516336]  ? kobject_put+0x16/0x60
[4.516340]  ? ata_dev_next+0xe7/0x220
[4.516345]  ata_scsi_scan_host+0x18f/0x2d0
[4.516349]  async_port_probe+0x5b/0xa0
[4.516353]  ? ata_port_probe+0x80/0x80
[4.516357]  async_run_entry_fn+0xe1/0x3b0
[4.516361]  ? current_is_async+0x70/0x70
[4.516364]  ? __schedule+0x487/0xde0
[4.516371]  ? pwq_dec_nr_in_flight+0xc9/0x1f0
[4.516375]  process_one_work+0x46a/0xb40
[4.516380]  ? cancel_delayed_work_sync+0x10/0x10
[4.516384]  ? worker_enter_idle+0x256/0x4d0
[4.516387]  ? pool_mayday_timeout+0x420/0x420
[4.516391]  worker_thread+0x10d/0x930
[4.516396]  ? process_one_work+0xb40/0xb40
[4.516400]  ? _raw_spin_unlock_bh+0xb0/0xb0
[4.516404]  ? __wake_up_common+0x90/0x140
[4.516407]  kthread+0x1cf/0x2b0
[4.516411]  ? process_one_work+0xb40/0xb40
[4.516414]  ? kthread_create_on_node+0xa0/0xa0
[4.516418]  ret_from_fork+0x29/0x40
[4.516421] Object at 8809, in cache dma-kmalloc-512 size: 512
[4.516421] Allocated:
[4.516422] PID = 677
[4.516426]  save_stack_trace+0x16/0x20
[4.516429]  save_stack+0x46/0xd0
[4.516432]  kasan_kmalloc+0xad/0xe0
[4.516434]  __kmalloc+0x123/0x2f0
[4.516437]  sr_probe+0x3a4/0xdc0
[4.516441]  driver_probe_device+0x1bf/0x4f0
[4.516444]  __device_attach_driver+0xf8/0x1b0
[4.516448]  bus_for_each_drv+0xfe/0x190
[4.516451]  __device_attach+0x16e/0x200
[4.516454]  device_initial_probe+0xe/0x10
[4.516458]  bus_probe_device+0x124/0x190
[4.516461]  device_add+0x883/0xb10
[4.516464]  scsi_sysfs_add_sdev+0xdb/0x450
[4.516468]  scsi_probe_and_add_lun+0x13da/0x1630
[4.516472]  __scsi_add_device+0x1a1/0x1c0
[4.516474]  ata_scsi_scan_host+0x18f/0x2d0
[4.516478]  async_port_probe+0x5b/0xa0
[4.516482]  async_run_entry_fn+0xe1/0x3b0
[