binder: fix use-after-free in binderfs_evict_inode()
CVE: CVE-2025-38176
Component: kernel
Severity: None
Release date: 2025-07-04T00:00:00+00:00

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

binder: fix use-after-free in binderfs_evict_inode()

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.


Remediation: