Vulnerability CVE-2024-38621
Published: 2024-06-21

Description:
In the Linux kernel, the following vulnerability has been resolved:

media: stk1160: fix bounds checking in stk1160_copy_video()

The subtract in this condition is reversed. The ->length is the length
of the buffer. The ->bytesused is how many bytes we have copied thus
far. When the condition is reversed that means the result of the
subtraction is always negative but since it's unsigned then the result
is a very high positive value. That means the overflow check is never
true.

Additionally, the ->bytesused doesn't actually work for this purpose
because we're not writing to "buf->mem + buf->bytesused". Instead, the
math to calculate the destination where we are writing is a bit
involved. You calculate the number of full lines already written,
multiply by two, skip a line if necessary so that we start on an odd
numbered line, and add the offset into the line.

To fix this buffer overflow, just take the actual destination where we
are writing, if the offset is already out of bounds print an error and
return. Otherwise, write up to buf->length bytes.

 References:
https://git.kernel.org/stable/c/f6a392266276730bea893b55d12940e32a25f56a
https://git.kernel.org/stable/c/ecf4ddc3aee8ade504c4d36b7b4053ce6093e200
https://git.kernel.org/stable/c/a16775828aaed1c54ff4e6fe83e8e4d5c6a50cb7
https://git.kernel.org/stable/c/7532bcec0797adfa08791301c3bcae14141db3bd
https://git.kernel.org/stable/c/b504518a397059e1d55c521ba0ea2b545a6c4b52
https://git.kernel.org/stable/c/d410017a7181cb55e4a5c810b32b75e4416c6808
https://git.kernel.org/stable/c/a08492832cc4cacc24e0612f483c86ca899b9261
https://git.kernel.org/stable/c/faa4364bef2ec0060de381ff028d1d836600a381
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