[PATCH 4/14] drivers/media/v4l2-core/videobuf2-core.c: fix error return code

[PATCH 4/14] drivers/media/v4l2-core/videobuf2-core.c: fix error return code

[Peter Senna Tschudin]

From: Peter Senna Tschudin <peter.senna@gmail.com>

Convert a nonnegative error return code to a negative one, as returned
elsewhere in the function.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
(
if@p1 (\(ret < 0\|ret != 0\))
 { ... return ret; }
|
ret@p1 = 0
)
... when != ret = e1
    when != &ret
*if(...)
{
  ... when != ret = e2
      when forall
 return ret;
}

// </smpl>

Signed-off-by: Peter Senna Tschudin <peter.senna@gmail.com>

---
 drivers/media/v4l2-core/videobuf2-core.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index 4da3df6..f6bc240 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -1876,8 +1876,10 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
 	 */
 	for (i = 0; i < q->num_buffers; i++) {
 		fileio->bufs[i].vaddr = vb2_plane_vaddr(q->bufs[i], 0);
-		if (fileio->bufs[i].vaddr == NULL)
+		if (fileio->bufs[i].vaddr == NULL) {
+			ret = -EFAULT;
 			goto err_reqbufs;
+		}
 		fileio->bufs[i].size = vb2_plane_size(q->bufs[i], 0);
 	}
 

Re: [PATCH 4/14] drivers/media/v4l2-core/videobuf2-core.c: fix error return code

[Mauro Carvalho Chehab]

Em Thu,  6 Sep 2012 17:23:57 +0200
Peter Senna Tschudin <peter.senna@gmail.com> escreveu:

> From: Peter Senna Tschudin <peter.senna@gmail.com>
> 
> Convert a nonnegative error return code to a negative one, as returned
> elsewhere in the function.
> 
> A simplified version of the semantic match that finds this problem is as
> follows: (http://coccinelle.lip6.fr/)
> 
> // <smpl>
> (
> if@p1 (\(ret < 0\|ret != 0\))
>  { ... return ret; }
> |
> ret@p1 = 0
> )
> ... when != ret = e1
>     when != &ret
> *if(...)
> {
>   ... when != ret = e2
>       when forall
>  return ret;
> }
> 
> // </smpl>
> 
> Signed-off-by: Peter Senna Tschudin <peter.senna@gmail.com>
> 
> ---
>  drivers/media/v4l2-core/videobuf2-core.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
> index 4da3df6..f6bc240 100644
> --- a/drivers/media/v4l2-core/videobuf2-core.c
> +++ b/drivers/media/v4l2-core/videobuf2-core.c
> @@ -1876,8 +1876,10 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
>  	 */
>  	for (i = 0; i < q->num_buffers; i++) {
>  		fileio->bufs[i].vaddr = vb2_plane_vaddr(q->bufs[i], 0);
> -		if (fileio->bufs[i].vaddr == NULL)
> +		if (fileio->bufs[i].vaddr == NULL) {
> +			ret = -EFAULT;
>  			goto err_reqbufs;
> +		}

Had you test this patch? I suspect it breaks the driver, as there are failures under
streaming handling that are acceptable, as it may indicate that userspace was not
able to handle all queued frames in time. On such cases, what the Kernel does is to
just discard the frame. Userspace is able to detect it, by looking inside the timestamp
added on each frame.

>  		fileio->bufs[i].size = vb2_plane_size(q->bufs[i], 0);
>  	}
>  
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-media" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html




Cheers,
Mauro

Re: [PATCH 4/14] drivers/media/v4l2-core/videobuf2-core.c: fix error return code

[Peter Senna Tschudin]

On Sat, Oct 6, 2012 at 1:17 PM, Mauro Carvalho Chehab
<mchehab@infradead.org> wrote:
> Em Thu,  6 Sep 2012 17:23:57 +0200
> Peter Senna Tschudin <peter.senna@gmail.com> escreveu:
>
>> From: Peter Senna Tschudin <peter.senna@gmail.com>
>>
>> Convert a nonnegative error return code to a negative one, as returned
>> elsewhere in the function.
>>
>> A simplified version of the semantic match that finds this problem is as
>> follows: (http://coccinelle.lip6.fr/)
>>
>> // <smpl>
>> (
>> if@p1 (\(ret < 0\|ret != 0\))
>>  { ... return ret; }
>> |
>> ret@p1 = 0
>> )
>> ... when != ret = e1
>>     when != &ret
>> *if(...)
>> {
>>   ... when != ret = e2
>>       when forall
>>  return ret;
>> }
>>
>> // </smpl>
>>
>> Signed-off-by: Peter Senna Tschudin <peter.senna@gmail.com>
>>
>> ---
>>  drivers/media/v4l2-core/videobuf2-core.c |    4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
>> index 4da3df6..f6bc240 100644
>> --- a/drivers/media/v4l2-core/videobuf2-core.c
>> +++ b/drivers/media/v4l2-core/videobuf2-core.c
>> @@ -1876,8 +1876,10 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
>>        */
>>       for (i = 0; i < q->num_buffers; i++) {
>>               fileio->bufs[i].vaddr = vb2_plane_vaddr(q->bufs[i], 0);
>> -             if (fileio->bufs[i].vaddr == NULL)
>> +             if (fileio->bufs[i].vaddr == NULL) {
>> +                     ret = -EFAULT;
>>                       goto err_reqbufs;
>> +             }
>
> Had you test this patch? I suspect it breaks the driver, as there are failures under
> streaming handling that are acceptable, as it may indicate that userspace was not
> able to handle all queued frames in time. On such cases, what the Kernel does is to
> just discard the frame. Userspace is able to detect it, by looking inside the timestamp
> added on each frame.

No, I have not tested it. This was the only place the function was
returning non negative value for error path, so looked as a bug to me.
May I add a comment about returning non-negative value is intended
there?

>
>>               fileio->bufs[i].size = vb2_plane_size(q->bufs[i], 0);
>>       }
>>
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-media" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>
>
>
> Cheers,
> Mauro



-- 
Peter

Re: [PATCH 4/14] drivers/media/v4l2-core/videobuf2-core.c: fix error return code

[Sylwester Nawrocki]

Hi Peter,

On 10/10/2012 06:47 PM, Peter Senna Tschudin wrote:
>>> diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
>>> index 4da3df6..f6bc240 100644
>>> --- a/drivers/media/v4l2-core/videobuf2-core.c
>>> +++ b/drivers/media/v4l2-core/videobuf2-core.c
>>> @@ -1876,8 +1876,10 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
>>>        */
>>>       for (i = 0; i < q->num_buffers; i++) {
>>>               fileio->bufs[i].vaddr = vb2_plane_vaddr(q->bufs[i], 0);
>>> -             if (fileio->bufs[i].vaddr == NULL)
>>> +             if (fileio->bufs[i].vaddr == NULL) {
>>> +                     ret = -EFAULT;
>>>                       goto err_reqbufs;
>>> +             }
>>
>> Had you test this patch? I suspect it breaks the driver, as there are failures under
>> streaming handling that are acceptable, as it may indicate that userspace was not
>> able to handle all queued frames in time. On such cases, what the Kernel does is to
>> just discard the frame. Userspace is able to detect it, by looking inside the timestamp
>> added on each frame.
> 
> No, I have not tested it. This was the only place the function was
> returning non negative value for error path, so looked as a bug to me.
> May I add a comment about returning non-negative value is intended
> there?

There are several drivers depending on core modules like videobuf2. By making
random changes for something that _looks like_ a bug to you and not verifying
it by testing with at least one driver you are potentially causing trouble to
developers that are already busy fixing real bugs or working on new features.

I appreciate your help but I also don't want to see _any_ untested, not trivial
patches for core modules like videobuf2 being applied.

--
Thanks,
Sylwester

[PATCH V2] drivers/media/v4l2-core/videobuf2-core.c: fix error return code

[Peter Senna Tschudin]

This patch fixes a NULL pointer dereference bug at __vb2_init_fileio().
The NULL pointer deference happens at videobuf2-core.c:

static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_t count,
                loff_t *ppos, int nonblock, int read)
{
...
        if (!q->fileio) {
                ret = __vb2_init_fileio(q, read);
                dprintk(3, "file io: vb2_init_fileio result: %d\n", ret);
                if (ret)
                        return ret;
        }
        fileio = q->fileio; // NULL pointer deference here
...
}

It was tested with vivi driver and qv4l2 for selecting read() as capture method.
The OOPS happened when I've artificially forced the error by commenting the line:
	if (fileio->bufs[i].vaddr == NULL)

But it was fixed after applying this patch.

[ 9002.451154] BUG: unable to handle kernel NULL pointer dereference at 0000000000000370
[ 9002.451266] IP: [<ffffffffa038c429>] __vb2_perform_fileio+0x69/0x620 [videobuf2_core]
[ 9002.451365] PGD 1df491067 PUD 196d12067 PMD 0
[ 9002.451431] Oops: 0000 [#1] SMP
[ 9002.451481] Modules linked in: vivi(O) v4l2_common videobuf2_core(O) videobuf2_vmalloc(O) videobuf2_memops(O) videodev hidp fuse ebtable_nat ebtables snd_hda_codec_hdmi snd_hda_codec_realtek ipt_MASQUERADE iptable_nat nf_nat xt_CHECKSUM iptable_mangle lockd sunrpc bridge stp llc rfcomm bnep btusb bluetooth pl2303 ip6t_REJECT snd_usb_audio nf_conntrack_ipv6 nf_defrag_ipv6 snd_usbmidi_lib snd_rawmidi ip6table_filter nf_conntrack_ipv4 ip6_tables nf_defrag_ipv4 xt_state nf_conntrack be2iscsi iscsi_boot_sysfs bnx2i cnic uio cxgb4i cxgb4 cxgb3i cxgb3 mdio libcxgbi ib_iser rdma_cm ib_addr iw_cm ib_cm ib_sa ib_mad ib_core iscsi_tcp libiscsi_tcp \
libiscsi scsi_transport_iscsi iTCO_wdt iTCO_vendor_support arc4 binfmt_misc media iwldvm mac80211 coretemp snd_hda_intel snd_hda_codec crc32c_intel snd_hwdep ghash_clmulni_intel snd_seq snd_seq_device microcode snd_pcm cdc_ncm usbnet mii cdc_wdm cdc_acm i915 snd_page_alloc i2c_algo_bit drm_kms_helper iwlwifi lpc_ich snd_timer sdhci_pci mfd_core drm toshiba_acpi sdhci snd sparse_keymap e1000e mmc_core cfg80211 i2c_core soundcore mei rfkill wmi video toshiba_bluetooth vhost_net tun macvtap macvlan kvm_intel kvm uinput [last unloaded: videobuf2_memops]
[ 9002.453105] CPU 1
[ 9002.453136] Pid: 13830, comm: qv4l2 Tainted: G           O 3.6.1-1.local.fc17.x86_64 #1 TOSHIBA PORTEGE R830/Portable PC
[ 9002.453251] RIP: 0010:[<ffffffffa038c429>]  [<ffffffffa038c429>] __vb2_perform_fileio+0x69/0x620 [videobuf2_core]
[ 9002.453368] RSP: 0018:ffff8801ed37fdf8  EFLAGS: 00010246
[ 9002.453427] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000011b55
[ 9002.453502] RDX: 0000000000011b54 RSI: ffff88024e256f68 RDI: ffff88023fdc9c00
[ 9002.453576] RBP: ffff8801ed37fe58 R08: 0000000000016aa0 R09: 0000000000000001
[ 9002.453651] R10: 0000000000000075 R11: 0000000000000800 R12: ffff8801bcde0580
[ 9002.453726] R13: ffff8801bcde0608 R14: 00000000000e1000 R15: 00000000024f0ee0
[ 9002.453801] FS:  00007f19308f17c0(0000) GS:ffff88024e240000(0000) knlGS:0000000000000000
[ 9002.453886] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 9002.453948] CR2: 0000000000000370 CR3: 00000001df7df000 CR4: 00000000000407e0
[ 9002.454023] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 9002.454098] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 9002.454175] Process qv4l2 (pid: 13830, threadinfo ffff8801ed37e000, task ffff8801f24b9710)
[ 9002.454260] Stack:
[ 9002.454284]  0000000000000000 0000000000000000 0000000000000800 0000000000000001
[ 9002.454379]  ffff8801ed37ff50 0000000000000000 ffff88023d56c610 ffff8801bcde0108
[ 9002.454473]  ffff8801bcde0580 00000000000e1000 ffff8801ed37ff50 ffff88023d56c600
[ 9002.454566] Call Trace:
[ 9002.454604]  [<ffffffffa038cb54>] vb2_read+0x14/0x20 [videobuf2_core]
[ 9002.454676]  [<ffffffffa038cc07>] vb2_fop_read+0xa7/0x4a0 [videobuf2_core]
[ 9002.454757]  [<ffffffffa03dc5e0>] v4l2_read+0xf0/0x140 [videodev]
[ 9002.454853]  [<ffffffff8118e911>] ? rw_verify_area+0x61/0xf0
[ 9002.454918]  [<ffffffff8118eda9>] vfs_read+0xa9/0x180
[ 9002.454976]  [<ffffffff8118eeca>] sys_read+0x4a/0x90
[ 9002.455035]  [<ffffffff816226e9>] system_call_fastpath+0x16/0x1b
[ 9002.455100] Code: 4d 85 ff 48 c7 c0 ea ff ff ff 0f 84 b1 00 00 00 49 8b 9d f8 01 00 00 48 85 db 0f 84 32 04 00 00 49 c7 85 f8 01 00 00 00 00 00 00 <8b> 83 70 03 00 00 4c 63 c0 89 45 cc 4b 8d 04 40 4c 8d 64 c3 70
[ 9002.455605] RIP  [<ffffffffa038c429>] __vb2_perform_fileio+0x69/0x620 [videobuf2_core]
[ 9002.455697]  RSP <ffff8801ed37fdf8>
[ 9002.455746] CR2: 0000000000000370
[ 9002.485830] ---[ end trace e865b84b28e31f5b ]---

This was found when looking for functions that return non-negative
values on error. A simplified version of the semantic match that 
finds this problem is as follows: (http://coccinelle.lip6.fr/)

// <smpl>
(
if@p1 (\(ret < 0\|ret != 0\))
 { ... return ret; }
|
ret@p1 = 0
)
... when != ret = e1
    when != &ret
*if(...)
{
  ... when != ret = e2
      when forall
 return ret;
}

// </smpl>

Signed-off-by: Peter Senna Tschudin <peter.senna@gmail.com>
---
Changes from V1:
	Updated commit message

 drivers/media/v4l2-core/videobuf2-core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index 432df11..dad10af 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -1878,8 +1878,10 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
 	 */
 	for (i = 0; i < q->num_buffers; i++) {
 		fileio->bufs[i].vaddr = vb2_plane_vaddr(q->bufs[i], 0);
-		if (fileio->bufs[i].vaddr == NULL)
+		if (fileio->bufs[i].vaddr == NULL) {
+			ret = -EFAULT;
 			goto err_reqbufs;
+		}
 		fileio->bufs[i].size = vb2_plane_size(q->bufs[i], 0);
 	}
 
-- 
1.7.11.7

Re: [PATCH V2] drivers/media/v4l2-core/videobuf2-core.c: fix error return code

[Ezequiel Garcia]

On Thu, Oct 18, 2012 at 11:47 AM, Peter Senna Tschudin
<peter.senna@gmail.com> wrote:
> This patch fixes a NULL pointer dereference bug at __vb2_init_fileio().
> The NULL pointer deference happens at videobuf2-core.c:
>
> static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_t count,
>                 loff_t *ppos, int nonblock, int read)
> {
> ...
>         if (!q->fileio) {
>                 ret = __vb2_init_fileio(q, read);
>                 dprintk(3, "file io: vb2_init_fileio result: %d\n", ret);
>                 if (ret)
>                         return ret;
>         }
>         fileio = q->fileio; // NULL pointer deference here
> ...
> }
>
> It was tested with vivi driver and qv4l2 for selecting read() as capture method.
> The OOPS happened when I've artificially forced the error by commenting the line:
>         if (fileio->bufs[i].vaddr == NULL)
>

... but if you manually changed the original source, how
can this be a real BUG?

Or am I missing something here ?

    Ezequiel

Re: [PATCH V2] drivers/media/v4l2-core/videobuf2-core.c: fix error return code

[Peter Senna Tschudin]

On Thu, Oct 18, 2012 at 5:28 PM, Ezequiel Garcia <elezegarcia@gmail.com> wrote:
> On Thu, Oct 18, 2012 at 11:47 AM, Peter Senna Tschudin
> <peter.senna@gmail.com> wrote:
>> This patch fixes a NULL pointer dereference bug at __vb2_init_fileio().
>> The NULL pointer deference happens at videobuf2-core.c:
>>
>> static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_t count,
>>                 loff_t *ppos, int nonblock, int read)
>> {
>> ...
>>         if (!q->fileio) {
>>                 ret = __vb2_init_fileio(q, read);
>>                 dprintk(3, "file io: vb2_init_fileio result: %d\n", ret);
>>                 if (ret)
>>                         return ret;
>>         }
>>         fileio = q->fileio; // NULL pointer deference here
>> ...
>> }
>>
>> It was tested with vivi driver and qv4l2 for selecting read() as capture method.
>> The OOPS happened when I've artificially forced the error by commenting the line:
>>         if (fileio->bufs[i].vaddr == NULL)
>>
>
> ... but if you manually changed the original source, how
> can this be a real BUG?

It is supposed that under some circumstances, (fileio->bufs[i].vaddr
== NULL) can be true. 'While testing', my change forced the scenario
in which (fileio->bufs[i].vaddr == NULL) is true...

>
> Or am I missing something here ?
>
>     Ezequiel



-- 
Peter

Re: [PATCH V2] drivers/media/v4l2-core/videobuf2-core.c: fix error return code

[Sylwester Nawrocki]

On 10/18/2012 05:28 PM, Ezequiel Garcia wrote:
> On Thu, Oct 18, 2012 at 11:47 AM, Peter Senna Tschudin
> <peter.senna@gmail.com> wrote:
>> This patch fixes a NULL pointer dereference bug at __vb2_init_fileio().
>> The NULL pointer deference happens at videobuf2-core.c:
>>
>> static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_t count,
>>                 loff_t *ppos, int nonblock, int read)
>> {
>> ...
>>         if (!q->fileio) {
>>                 ret = __vb2_init_fileio(q, read);
>>                 dprintk(3, "file io: vb2_init_fileio result: %d\n", ret);
>>                 if (ret)
>>                         return ret;
>>         }
>>         fileio = q->fileio; // NULL pointer deference here
>> ...
>> }
>>
>> It was tested with vivi driver and qv4l2 for selecting read() as capture method.
>> The OOPS happened when I've artificially forced the error by commenting the line:
>>         if (fileio->bufs[i].vaddr == NULL)
>>
> 
> ... but if you manually changed the original source, how
> can this be a real BUG?
> 
> Or am I missing something here ?

He just commented out this line to trigger the bug, i.e. to simulate
a situation where fileio->bufs[i].vaddr is NULL. Which is now not
handled properly.

--
Thanks,
Sylwester