CVE-2026-99007

Description

In the Linux kernel, the following vulnerability has been resolved: drm/fb-helper: defer setup when fbdev_probe() fails, not just on -EAGAIN __drm_fb_helper_initial_config_and_unlock() calls drm_client_modeset_probe() first, which already fills in each mode_set->mode/num_connectors for every connected output, and only afterwards calls drm_fb_helper_single_fb_probe() to create fb_helper->fb and wire it into those mode_sets via drm_setup_crtcs_fb(). If drm_fb_helper_single_fb_probe() fails with anything other than -EAGAIN (e.g. dev->driver->fbdev_probe() itself fails), the function bails out before drm_setup_crtcs_fb() runs and before setting fb_helper->deferred_setup. The client is left with mode_sets that have a mode and connectors but mode_set->fb == NULL, and nothing marks this fb_helper as needing a retry. __drm_fb_helper_restore_fbdev_mode_unlocked() only skips committing when fb_helper->deferred_setup is set, so a later .restore() call (drm_lastclose() on process exit, in this report) commits the stale mode_set through drm_client_modeset_commit() -> drm_client_modeset_commit_atomic() -> __drm_atomic_helper_set_config(), which hits WARN_ON(!set->fb). Mark fb_helper->deferred_setup on any drm_fb_helper_single_fb_probe() failure, not just -EAGAIN, so restore keeps skipping the commit until a later hotplug event successfully re-probes and re-populates mode_set->fb. The real error code is still returned to the caller unchanged.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

References

• https://git.kernel.org/stable/c/4a2006c675758f0c765b36fec6b49d17e89159cf ↗
• https://git.kernel.org/stable/c/3b303696f61461b3569019d7fcac6a646652b2b4 ↗
• https://git.kernel.org/stable/c/4e7b508c7c60dec7a86b7eb2a1b7e6d174afa457 ↗
• https://git.kernel.org/stable/c/d510ed273854177f0a3ed330145858b2fe667f81 ↗
• https://git.kernel.org/stable/c/755c94d178b7e972bb766199d34e4ba4f63a89eb ↗