Affected: Alpaquita:25: linux-lts, Alpaquita:stream: linux-lts

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

mm/slub: avoid zeroing outside-object freepointer for single free

Commit 284f17ac13fe ("mm/slub: handle bulk and single object freeing separately") splits single and bulk object freeing in two functions slab_free() and slab_free_bulk() which leads slab_free() to call slab_free_hook() directly instead of slab_free_freelist_hook().

If `init_on_free` is set, slab_free_hook() zeroes the object. Afterward, if `slub_debug=F` and `CONFIG_SLAB_FREELIST_HARDENED` are set, the do_slab_free() slowpath executes freelist consistency checks and try to decode a zeroed freepointer which leads to a "Freepointer corrupt" detection in check_object().

During bulk free, slab_free_freelist_hook() isn't affected as it always sets it objects freepointer using set_freepointer() to maintain its reconstructed freelist after `init_on_free`.

For single free, object's freepointer thus needs to be avoided when stored outside the object if `init_on_free` is set. The freepointer left as is, check_object() may later detect an invalid pointer value due to objects overflow.

To reproduce, set `slub_debug=FU init_on_free=1 log_level=7` on the command line of a kernel build with `CONFIG_SLAB_FREELIST_HARDENED=y`.

dmesg sample log: [ 10.708715] ============================================================================= [ 10.710323] BUG kmalloc-rnd-05-32 (Tainted: G B T ): Freepointer corrupt [ 10.712695] ---------------…

Affected: Ubuntu:16.04:LTS: linux-hwe-edge, Ubuntu:18.04:LTS: linux-aws-5.0, Ubuntu:18.04:LTS: linux-aws-5.3, Ubuntu:18.04:LTS: linux-azure, Ubuntu:18.04:LTS: linux-azure-5.3, Ubuntu:18.04:LTS: linux-azure-edge, Ubuntu:18.04:LTS: linux-gcp, Ubuntu:18.04:LTS: linux-gcp-5.3, Ubuntu:18.04:LTS: linux-gke-4.15, Ubuntu:18.04:LTS: linux-gke-5.4 and 78 more

In the Linux kernel, the following vulnerability has been resolved: mm/slub: avoid zeroing outside-object freepointer for single free Commit 284f17ac13fe ("mm/slub: handle bulk and single object freeing separately") splits single and bulk object freeing in two functions slab_free() and slab_free_bulk() which leads slab_free() to call slab_free_hook() directly instead of slab_free_freelist_hook(). If `init_on_free` is set, slab_free_hook() zeroes the object. Afterward, if `slub_debug=F` and `CONFIG_SLAB_FREELIST_HARDENED` are set, the do_slab_free() slowpath executes freelist consistency checks and try to decode a zeroed freepointer which leads to a "Freepointer corrupt" detection in check_object(). During bulk free, slab_free_freelist_hook() isn't affected as it always sets it objects freepointer using set_freepointer() to maintain its reconstructed freelist after `init_on_free`. For single free, object's freepointer thus needs to be avoided when stored outside the object if `init_on_free` is set. The freepointer left as is, check_object() may later detect an invalid pointer value due to objects overflow. To reproduce, set `slub_debug=FU init_on_free=1 log_level=7` on the command line of a kernel build with `CONFIG_SLAB_FREELIST_HARDENED=y`. dmesg sample log: [ 10.708715] ============================================================================= [ 10.710323] BUG kmalloc-rnd-05-32 (Tainted: G B T ): Freepointer corrupt [ 10.712695] ----------------------…

Ein lokaler Angreifer kann mehrere Schwachstellen im Linux-Kernel ausnutzen, um einen Denial-of-Service-Zustand zu erzeugen oder einen unspezifischen Angriff durchzuführen.