From: Dmitry Antipov dmantipov@yandex.ru

Running 'stress-ng --binderfs 16 --timeout 300' under KASAN-enabled kernel, I've noticed the following:

BUG: KASAN: slab-use-after-free in binderfs_evict_inode+0x1de/0x2d0 Write of size 8 at addr ffff88807379bc08 by task stress-ng-binde/1699

CPU: 0 UID: 0 PID: 1699 Comm: stress-ng-binde Not tainted 6.14.0-rc7-g586de92313fc-dirty #13 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x1c2/0x2a0 ? __pfx_dump_stack_lvl+0x10/0x10 ? __pfx__printk+0x10/0x10 ? __pfx_lock_release+0x10/0x10 ? __virt_addr_valid+0x18c/0x540 ? __virt_addr_valid+0x469/0x540 print_report+0x155/0x840 ? __virt_addr_valid+0x18c/0x540 ? __virt_addr_valid+0x469/0x540 ? __phys_addr+0xba/0x170 ? binderfs_evict_inode+0x1de/0x2d0 kasan_report+0x147/0x180 ? binderfs_evict_inode+0x1de/0x2d0 binderfs_evict_inode+0x1de/0x2d0 ? __pfx_binderfs_evict_inode+0x10/0x10 evict+0x524/0x9f0 ? __pfx_lock_release+0x10/0x10 ? __pfx_evict+0x10/0x10 ? do_raw_spin_unlock+0x4d/0x210 ? _raw_spin_unlock+0x28/0x50 ? iput+0x697/0x9b0 __dentry_kill+0x209/0x660 ? shrink_kill+0x8d/0x2c0 shrink_kill+0xa9/0x2c0 shrink_dentry_list+0x2e0/0x5e0 shrink_dcache_parent+0xa2/0x2c0 ? __pfx_shrink_dcache_parent+0x10/0x10 ? __pfx_lock_release+0x10/0x10 ? __pfx_do_raw_spin_lock+0x10/0x10 do_one_tree+0x23/0xe0 shrink_dcache_for_umount+0xa0/0x170 generic_shutdown_super+0x67/0x390 kill_litter_super+0x76/0xb0 binderfs_kill_super+0x44/0x90 deactivate_locked_super+0xb9/0x130 cleanup_mnt+0x422/0x4c0 ? lockdep_hardirqs_on+0x9d/0x150 task_work_run+0x1d2/0x260 ? __pfx_task_work_run+0x10/0x10 resume_user_mode_work+0x52/0x60 syscall_exit_to_user_mode+0x9a/0x120 do_syscall_64+0x103/0x210 ? asm_sysvec_apic_timer_interrupt+0x1a/0x20 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0xcac57b Code: c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 f3 0f 1e fa 31 f6 e9 05 00 00 00 0f 1f 44 00 00 f3 0f 1e fa b8 RSP: 002b:00007ffecf4226a8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6 RAX: 0000000000000000 RBX: 00007ffecf422720 RCX: 0000000000cac57b RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007ffecf422850 RBP: 00007ffecf422850 R08: 0000000028d06ab1 R09: 7fffffffffffffff R10: 3fffffffffffffff R11: 0000000000000246 R12: 00007ffecf422718 R13: 00007ffecf422710 R14: 00007f478f87b658 R15: 00007ffecf422830 </TASK>

Allocated by task 1705: kasan_save_track+0x3e/0x80 __kasan_kmalloc+0x8f/0xa0 __kmalloc_cache_noprof+0x213/0x3e0 binderfs_binder_device_create+0x183/0xa80 binder_ctl_ioctl+0x138/0x190 __x64_sys_ioctl+0x120/0x1b0 do_syscall_64+0xf6/0x210 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 1705: kasan_save_track+0x3e/0x80 kasan_save_free_info+0x46/0x50 __kasan_slab_free+0x62/0x70 kfree+0x194/0x440 evict+0x524/0x9f0 do_unlinkat+0x390/0x5b0 __x64_sys_unlink+0x47/0x50 do_syscall_64+0xf6/0x210 entry_SYSCALL_64_after_hwframe+0x77/0x7f

This 'stress-ng' workload causes the concurrent deletions from 'binder_devices' and so requires full-featured synchronization to prevent list corruption.

I've found this issue independently but pretty sure that syzbot did the same, so Reported-by: and Closes: should be applicable here as well.

Cc: stable@vger.kernel.org Reported-by: syzbot+353d7b75658a95aa955a@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=353d7b75658a95aa955a Fixes: e77aff5528a18 ("binderfs: fix use-after-free in binder_devices") Signed-off-by: Dmitry Antipov dmantipov@yandex.ru Acked-by: Carlos Llamas cmllamas@google.com Signed-off-by: Carlos Llamas cmllamas@google.com --- v1: https://lore.kernel.org/all/20250324132427.922495-1-dmantipov@yandex.ru/

v2: - Collect tags. Actually Cc Greg and stable@ this time.

drivers/android/binder.c | 15 +++++++++++++-- drivers/android/binder_internal.h | 8 ++++++-- drivers/android/binderfs.c | 2 +- 3 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 5fc2c8ee61b1..8d9c5f436fca 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -79,6 +79,8 @@ static HLIST_HEAD(binder_deferred_list); static DEFINE_MUTEX(binder_deferred_lock);

static HLIST_HEAD(binder_devices); +static DEFINE_SPINLOCK(binder_devices_lock); + static HLIST_HEAD(binder_procs); static DEFINE_MUTEX(binder_procs_lock);

@@ -6929,7 +6931,16 @@ const struct binder_debugfs_entry binder_debugfs_entries[] = {

void binder_add_device(struct binder_device *device) { + spin_lock(&binder_devices_lock); hlist_add_head(&device->hlist, &binder_devices); + spin_unlock(&binder_devices_lock); +} + +void binder_remove_device(struct binder_device *device) +{ + spin_lock(&binder_devices_lock); + hlist_del_init(&device->hlist); + spin_unlock(&binder_devices_lock); }

static int __init init_binder_device(const char *name) @@ -6956,7 +6967,7 @@ static int __init init_binder_device(const char *name) return ret; }

- hlist_add_head(&binder_device->hlist, &binder_devices); + binder_add_device(binder_device);

return ret; } @@ -7018,7 +7029,7 @@ static int __init binder_init(void) err_init_binder_device_failed: hlist_for_each_entry_safe(device, tmp, &binder_devices, hlist) { misc_deregister(&device->miscdev); - hlist_del(&device->hlist); + binder_remove_device(device); kfree(device); }

diff --git a/drivers/android/binder_internal.h b/drivers/android/binder_internal.h index 6a66c9769c6c..1ba5caf1d88d 100644 --- a/drivers/android/binder_internal.h +++ b/drivers/android/binder_internal.h @@ -583,9 +583,13 @@ struct binder_object { /** * Add a binder device to binder_devices * @device: the new binder device to add to the global list - * - * Not reentrant as the list is not protected by any locks */ void binder_add_device(struct binder_device *device);

+/** + * Remove a binder device to binder_devices + * @device: the binder device to remove from the global list + */ +void binder_remove_device(struct binder_device *device); + #endif /* _LINUX_BINDER_INTERNAL_H */ diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c index 94c6446604fc..44d430c4ebef 100644 --- a/drivers/android/binderfs.c +++ b/drivers/android/binderfs.c @@ -274,7 +274,7 @@ static void binderfs_evict_inode(struct inode *inode) mutex_unlock(&binderfs_minors_mutex);

if (refcount_dec_and_test(&device->ref)) { - hlist_del_init(&device->hlist); + binder_remove_device(device); kfree(device->context.name); kfree(device); }