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

binder: fix yet another UAF in binder_devices

Commit e77aff5528a18 (binderfs: fix use-after-free in binder_devices) addressed a use-after-free where devices could be released without first being removed from the binder_devices list. However, there is a similar path in binder_free_proc() that was missed:

================================================================== BUG: KASAN: slab-use-after-free in binder_remove_device+0xd4/0x100 Write of size 8 at addr ffff0000c773b900 by task umount/467 CPU: 12 UID: 0 PID: 467 Comm: umount Not tainted 6.15.0-rc7-00138-g57483a362741 #9 PREEMPT Hardware name: linux,dummy-virt (DT) Call trace: binder_remove_device+0xd4/0x100 binderfs_evict_inode+0x230/0x2f0 evict+0x25c/0x5dc iput+0x304/0x480 dentry_unlink_inode+0x208/0x46c __dentry_kill+0x154/0x530 […]

Allocated by task 463: __kmalloc_cache_noprof+0x13c/0x324 binderfs_binder_device_create.isra.0+0x138/0xa60 binder_ctl_ioctl+0x1ac/0x230 […]

Freed by task 215: kfree+0x184/0x31c binder_proc_dec_tmpref+0x33c/0x4ac binder_deferred_func+0xc10/0x1108 process_one_work+0x520/0xba4 […]

Call binder_remove_device() within binder_free_proc() to ensure the device is removed from the binder_devices list before being kfreed.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/4a7694f499cae5b83412c5281bf2c961f34f2ed6
• https://git.kernel.org/stable/c/72a726fb5f25fbb31d6060acfb671c1955831245
• https://git.kernel.org/stable/c/9857af0fcff385c75433f2162c30c62eb912ef6d