drm/nouveau: RCU-free the scheduler-containing nouveau_sched

Overview

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

drm/nouveau: RCU-free the scheduler-containing nouveau_sched

struct nouveau_sched embeds a struct drm_gpu_scheduler (base). nouveau_sched_destroy() calls nouveau_sched_fini() (which does drm_sched_fini(&sched->base)) and then frees the object with plain kfree(sched).

drm_sched_fence_get_timeline_name() returns fence->sched->name, and the scheduler fence keeps a .release callback so it is not ops-detached on signalling. A finished fence exported to userspace via drm_syncobj / sync_file therefore keeps pointing at &sched->base after nouveau_sched_destroy(), and a later get_timeline_name() -- reachable unprivileged through SYNC_IOC_FILE_INFO -- dereferences freed memory (KASAN slab-use-after-free read).

Per the dma-fence lifetime contract the exporter must keep the data backing a signalled fence alive for an RCU grace period. Free the scheduler-containing object with kfree_rcu() instead of kfree().

Affected

• Linux >= 5f03a507b29e44a848f315c7240c19894dd8be4f < 40edf5eefc3fd94592a91d6eb074d4fc6f606c75
• Linux >= 5f03a507b29e44a848f315c7240c19894dd8be4f < 35151e9a8274174ccbb92e3b3ba7dc7a008dcada
• Linux >= 5f03a507b29e44a848f315c7240c19894dd8be4f < cd6e11b6ebe04a0a1f1435df561acada9eadc563
• Linux >= 5f03a507b29e44a848f315c7240c19894dd8be4f < f7eae6d8d768fabd6b59779ca7da79e02c74e113
• Linux 6.8

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.