Re: [PATCH] omap_vout: Added check in reqbuf & mmap for buf_size allocation

[Archit Taneja]

Hi,

On Friday 17 June 2011 03:33 PM, Hiremath, Vaibhav wrote:

-----Original Message-----
From: Taneja, Archit
Sent: Friday, June 17, 2011 2:16 PM
To: Hiremath, Vaibhav
Cc: linux-media@vger.kernel.org; mche...@redhat.com; hverk...@xs4all.nl
Subject: Re: [PATCH] omap_vout: Added check in reqbuf&  mmap for buf_size
allocation

Hi,

On Friday 17 June 2011 01:44 AM, Hiremath, Vaibhav wrote:
From: Vaibhav Hiremath<hvaib...@ti.com>

The usecase where, user allocates small size of buffer
through bootargs (video1_bufsize/video2_bufsize) and later from
application
tries to set the format which requires larger buffer size, driver
doesn't
check for insufficient buffer size and allows application to map extra
buffer.
This leads to kernel crash, when user application tries to access memory
beyond the allocation size.

Query: Why do we pass the bufsize as bootargs in the first place? Is it
needed at probe time?

[Hiremath, Vaibhav] Yes, look out for variable (video1_bufsize/video2_bufsize) 
in code.

Yes, but why do we need to allocate some fixed size buffers at boot 
time? Is it done because it makes our allocation happens faster during 
reqbufs? Or is it required for VRFB?

Could you explain the reason/startegy behind allocating buffers of a 
particular size at boot time?

Thanks,
Archit


Thanks,
Vaibhav

Thanks,
Archit


Added check in both mmap and reqbuf call back function,
and return error if the size of the buffer allocated by user through
bootargs is less than the S_FMT size.

Signed-off-by: Vaibhav Hiremath<hvaib...@ti.com>
---
   drivers/media/video/omap/omap_vout.c |   16 ++++++++++++++++
   1 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/drivers/media/video/omap/omap_vout.c
b/drivers/media/video/omap/omap_vout.c
index 3bc909a..343b50c 100644
--- a/drivers/media/video/omap/omap_vout.c
+++ b/drivers/media/video/omap/omap_vout.c
@@ -678,6 +678,14 @@ static int omap_vout_buffer_setup(struct
videobuf_queue *q, unsigned int *count,
        startindex = (vout->vid == OMAP_VIDEO1) ?
                video1_numbuffers : video2_numbuffers;

+       /* Check the size of the buffer */
+       if (*size>   vout->buffer_size) {
+               v4l2_err(&vout->vid_dev->v4l2_dev,
+                               "buffer allocation mismatch [%u] [%u]\n",
+                               *size, vout->buffer_size);
+               return -ENOMEM;
+       }
+
        for (i = startindex; i<   *count; i++) {
                vout->buffer_size = *size;

@@ -856,6 +864,14 @@ static int omap_vout_mmap(struct file *file, struct
vm_area_struct *vma)
                                (vma->vm_pgoff<<   PAGE_SHIFT));
                return -EINVAL;
        }
+       /* Check the size of the buffer */
+       if (size>   vout->buffer_size) {
+               v4l2_err(&vout->vid_dev->v4l2_dev,
+                               "insufficient memory [%lu] [%u]\n",
+                               size, vout->buffer_size);
+               return -ENOMEM;
+       }
+
        q->bufs[i]->baddr = vma->vm_start;

        vma->vm_flags |= VM_RESERVED;
--
1.6.2.4

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