CVE-2024-56616

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

drm/dp_mst: Fix MST sideband message body length check

Fix the MST sideband message body length check, which must be at least 1 byte accounting for the message body CRC (aka message data CRC) at the end of the message.

This fixes a case where an MST branch device returns a header with a correct header CRC (indicating a correctly received body length), with the body length being incorrectly set to 0. This will later lead to a memory corruption in drmdpsidebandappendpayload() and the following errors in dmesg:

UBSAN: array-index-out-of-bounds in drivers/gpu/drm/display/drmdpmsttopology.c:786:25 index -1 is out of range for type 'u8 [48]' Call Trace: drmdpsidebandappendpayload+0x33d/0x350 [drmdisplayhelper] drmdpgetonesbmsg+0x3ce/0x5f0 [drmdisplayhelper] drmdpmsthpdirqhandleevent+0xc8/0x1580 [drmdisplayhelper]

memcpy: detected field-spanning write (size 18446744073709551615) of single field "&msg->msg[msg->curlen]" at drivers/gpu/drm/display/drmdpmsttopology.c:791 (size 256) Call Trace: drmdpsidebandappendpayload+0x324/0x350 [drmdisplayhelper] drmdpgetonesbmsg+0x3ce/0x5f0 [drmdisplayhelper] drmdpmsthpdirqhandleevent+0xc8/0x1580 [drmdisplayhelper]