From 9857af0fcff385c75433f2162c30c62eb912ef6d Mon Sep 17 00:00:00 2001 From: Carlos Llamas Date: Sat, 24 May 2025 22:07:58 +0000 Subject: [PATCH] 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. Cc: stable@vger.kernel.org Fixes: 12d909cac1e1 ("binderfs: add new binder devices to binder_devices") Reported-by: syzbot+4af454407ec393de51d6@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=4af454407ec393de51d6 Tested-by: syzbot+4af454407ec393de51d6@syzkaller.appspotmail.com Signed-off-by: Carlos Llamas Link: https://lore.kernel.org/r/20250524220758.915028-1-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 682bbe4ad550..c463ca4a8fff 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -5241,6 +5241,7 @@ static void binder_free_proc(struct binder_proc *proc) __func__, proc->outstanding_txns); device = container_of(proc->context, struct binder_device, context); if (refcount_dec_and_test(&device->ref)) { + binder_remove_device(device); kfree(proc->context->name); kfree(device); } -- 2.25.1