Description

In the Linux kernel, the following vulnerability has been resolved: drm/v3d: Reject empty multisync extension to prevent infinite loop v3d_get_extensions() walks a userspace-provided singly-linked list of ioctl extensions without any bound on the chain length. A local user can craft a self-referential extension (ext->next == &ext) with zero in_sync_count and out_sync_count, which bypasses the existing duplicate- extension guard: if (se->in_sync_count || se->out_sync_count) return -EINVAL; The guard never fires because v3d_get_multisync_post_deps() returns immediately when count is zero, leaving both fields at zero on every iteration. The result is an infinite loop in kernel context, blocking the calling thread and pegging a CPU core indefinitely. Fix this by rejecting a multisync extension where both in_sync_count and out_sync_count are zero in v3d_get_multisync_submit_deps(). An empty multisync carries no synchronization information and serves no useful purpose, so returning -EINVAL for such an extension is the correct defense against this attack vector.

References 4

• git.kernel.org https://git.kernel.org/stable/c/309abbddeca0c12714721928a819ef45e5710998
• git.kernel.org https://git.kernel.org/stable/c/4fa42a249e8cd6ed17aea04e5695b6e9001f2433
• git.kernel.org https://git.kernel.org/stable/c/9c5164781cb388d219d8f49fa0f0b04cf86ad544
• git.kernel.org https://git.kernel.org/stable/c/fb44d589bf3148e13452185a6e772a7efbf2d684

Remediation