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

binder: fix double-free in dbitmap

A process might fail to allocate a new bitmap when trying to expand its proc->dmap. In that case, dbitmap_grow() fails and frees the old bitmap via dbitmap_free(). However, the driver calls dbitmap_free() again when the same process terminates, leading to a double-free error:

================================================================== BUG: KASAN: double-free in binder_proc_dec_tmpref+0x2e0/0x55c Free of addr ffff00000b7c1420 by task kworker/9:1/209

CPU: 9 UID: 0 PID: 209 Comm: kworker/9:1 Not tainted 6.17.0-rc6-dirty #5 PREEMPT Hardware name: linux,dummy-virt (DT) Workqueue: events binder_deferred_func Call trace: kfree+0x164/0x31c binder_proc_dec_tmpref+0x2e0/0x55c binder_deferred_func+0xc24/0x1120 process_one_work+0x520/0xba4 […]

Allocated by task 448: __kmalloc_noprof+0x178/0x3c0 bitmap_zalloc+0x24/0x30 binder_open+0x14c/0xc10 […]

Freed by task 449: kfree+0x184/0x31c binder_inc_ref_for_node+0xb44/0xe44 binder_transaction+0x29b4/0x7fbc binder_thread_write+0x1708/0x442c binder_ioctl+0x1b50/0x2900 […]

Fix this issue by marking proc->map NULL in dbitmap_free().

Affected Software

References

• https://git.kernel.org/stable/c/0390633979969c54c0ce6a198d6f45cdbe2c84b1
• https://git.kernel.org/stable/c/3ebcd3460cad351f198c39c6edb4af519a0ed934
• https://git.kernel.org/stable/c/b781e5635a3398e2b64440371233c2c5102cd6cb
• https://git.kernel.org/stable/c/c301ec61ce6f16e21a36b99225ca8a20c1591e10