media: s2255: bound JPEG frame size before copying into the buffer

In the Linux kernel, the following vulnerability has been resolved: media: s2255: bound JPEG frame size before copying into the buffer s2255_fillbuff() memcpy()s vc->jpg_size bytes of a captured JPEG/MJPEG frame into the vb2 plane. vc->jpg_size is taken verbatim from the S2255_MARKER_FRAME header the device sends (pdword[4] in save_frame()) and, unlike the frame payload length just above it, is never bounded: payload = le32_to_cpu(pdword[3]); if (payload > vc->req_image_size) /* payload is checked ... */ return -EINVAL; vc->pkt_size = payload; vc->jpg_size = le32_to_cpu(pdword[4]); /* ... jpg_size is not */ A malicious or malfunctioning device can therefore report a jpg_size larger than the destination vb2 plane, and the memcpy() writes past it. jpg_size is a signed int, so a value with the top bit set also turns into a huge length. Reject a frame whose jpg_size is negative or exceeds the plane size before copying it.