Description
In the Linux kernel, the following vulnerability has been resolved: drm: Don't unref the same fb many times by mistake due to deadlock handling If we get a deadlock after the fb lookup in drm_mode_page_flip_ioctl() we proceed to unref the fb and then retry the whole thing from the top. But we forget to reset the fb pointer back to NULL, and so if we then get another error during the retry, before the fb lookup, we proceed the unref the same fb again without having gotten another reference. The end result is that the fb will (eventually) end up being freed while it's still in use. Reset fb to NULL once we've unreffed it to avoid doing it again until we've done another fb lookup. This turned out to be pretty easy to hit on a DG2 when doing async flips (and CONFIG_DEBUG_WW_MUTEX_SLOWPATH=y). The first symptom I saw that drm_closefb() simply got stuck in a busy loop while walking the framebuffer list. Fortunately I was able to convince it to oops instead, and from there it was easier to track down the culprit.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
29dc0d1de18239cf3ef8bab578b8321ed340d81c to < 376e21a9e4c2c63ee5d8d3aa74be5082c3882229affected29dc0d1de18239cf3ef8bab578b8321ed340d81c to < 9dd334a8245011ace45e53298175c7b659edb3e7affected29dc0d1de18239cf3ef8bab578b8321ed340d81c to < f55261469be87c55df13db76dc945f6bcd825105affected29dc0d1de18239cf3ef8bab578b8321ed340d81c to < b4af63da9d94986c529d74499fdfe44289acd551affected29dc0d1de18239cf3ef8bab578b8321ed340d81c to < 62f2e79cf9f4f47cc9dea9cebdf58d9f7b5695e0affected29dc0d1de18239cf3ef8bab578b8321ed340d81c to < d7afdf360f4ac142832b098b4de974e867cc063caffected29dc0d1de18239cf3ef8bab578b8321ed340d81c to < bfd0feb1b109cb63b87fdcd00122603787c75a1aaffected29dc0d1de18239cf3ef8bab578b8321ed340d81c to < cb4daf271302d71a6b9a7c01bd0b6d76febd8f0caffected
Linux Linux
Default version status: affected
4.12affected0 to < 4.12unaffected4.19.307 to ≤ 4.19.*unaffected5.4.269 to ≤ 5.4.*unaffected5.10.210 to ≤ 5.10.*unaffected5.15.149 to ≤ 5.15.*unaffected6.1.76 to ≤ 6.1.*unaffected6.6.15 to ≤ 6.6.*unaffected6.7.3 to ≤ 6.7.*unaffected6.8 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/376e21a9e4c2c63ee5d8d3aa74be5082c3882229 ↗
- https://git.kernel.org/stable/c/9dd334a8245011ace45e53298175c7b659edb3e7 ↗
- https://git.kernel.org/stable/c/f55261469be87c55df13db76dc945f6bcd825105 ↗
- https://git.kernel.org/stable/c/b4af63da9d94986c529d74499fdfe44289acd551 ↗
- https://git.kernel.org/stable/c/62f2e79cf9f4f47cc9dea9cebdf58d9f7b5695e0 ↗
- https://git.kernel.org/stable/c/d7afdf360f4ac142832b098b4de974e867cc063c ↗
- https://git.kernel.org/stable/c/bfd0feb1b109cb63b87fdcd00122603787c75a1a ↗
- https://git.kernel.org/stable/c/cb4daf271302d71a6b9a7c01bd0b6d76febd8f0c ↗
- https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html ↗
- https://lists.debian.org/debian-lts-announce/2024/06/msg00020.html ↗