While running selftest binderfs_test on linux mainline the following warning on arm64, arm, x86_64 and i386.
[ 329.383391] refcount_t: underflow; use-after-free. [ 329.391025] WARNING: CPU: 0 PID: 2604 at /usr/src/kernel/lib/refcount.c:28 refcount_warn_saturate+0xd4/0x150 [ 329.403319] Modules linked in: cls_bpf sch_fq algif_hash af_alg rfkill tda998x drm_kms_helper drm crct10dif_ce fuse [ 329.413828] CPU: 0 PID: 2604 Comm: binderfs_test Not tainted 5.6.0-rc5 #1 [ 329.420640] Hardware name: ARM Juno development board (r2) (DT) [ 329.426584] pstate: 40000005 (nZcv daif -PAN -UAO) [ 329.431402] pc : refcount_warn_saturate+0xd4/0x150 [ 329.436216] lr : refcount_warn_saturate+0xd4/0x150 [ 329.441026] sp : ffff800013d03a70 [ 329.444356] x29: ffff800013d03a70 x28: ffff00092c3f8000 [ 329.449694] x27: 0000000000000000 x26: ffff80001236f000 [ 329.455033] x25: ffff800012656000 x24: 0000000000000001 [ 329.460371] x23: ffff800012656f76 x22: ffff80001265b2c0 [ 329.465709] x21: ffff000929035c00 x20: ffff00095cd8ce00 [ 329.471048] x19: ffff80001261c848 x18: ffffffffffffffff [ 329.476386] x17: 0000000000000000 x16: 0000000000000000 [ 329.481724] x15: ffff80001236fa88 x14: ffff800093d03767 [ 329.487062] x13: ffff800013d03775 x12: ffff80001239e000 [ 329.492400] x11: 0000000005f5e0ff x10: ffff800013d03700 [ 329.497738] x9 : ffff8000126ddc68 x8 : 0000000000000028 [ 329.503076] x7 : ffff800010190a5c x6 : ffff00097ef0b428 [ 329.508414] x5 : ffff00097ef0b428 x4 : ffff00092c3f8000 [ 329.513752] x3 : ffff800012370000 x2 : 0000000000000000 [ 329.519090] x1 : 295161095161e100 x0 : 0000000000000000 [ 329.524429] Call trace: [ 329.526894] refcount_warn_saturate+0xd4/0x150 [ 329.531362] binderfs_evict_inode+0xcc/0xe8 [ 329.535567] evict+0xa8/0x188 [ 329.538552] iput+0x278/0x318 [ 329.541537] dentry_unlink_inode+0x154/0x170 [ 329.545827] __dentry_kill+0xc4/0x1d8 [ 329.549509] shrink_dentry_list+0xf4/0x210 [ 329.553625] shrink_dcache_parent+0x124/0x210 [ 329.558002] do_one_tree+0x20/0x50 [ 329.561423] shrink_dcache_for_umount+0x30/0x98 [ 329.565975] generic_shutdown_super+0x2c/0xf8 [ 329.570354] kill_anon_super+0x24/0x48 [ 329.574122] kill_litter_super+0x2c/0x38 [ 329.578065] binderfs_kill_super+0x24/0x48 [ 329.582182] deactivate_locked_super+0x74/0xa0 [ 329.586647] deactivate_super+0x8c/0x98 [ 329.590502] cleanup_mnt+0xd8/0x130 [ 329.594008] __cleanup_mnt+0x20/0x30 [ 329.597605] task_work_run+0x90/0x150 [ 329.601287] do_notify_resume+0x130/0x498 [ 329.605317] work_pending+0x8/0x14 [ 329.608736] irq event stamp: 1612 [ 329.612072] hardirqs last enabled at (1611): [<ffff800010190bf4>] console_unlock+0x514/0x5d8 [ 329.620631] hardirqs last disabled at (1612): [<ffff8000100a904c>] debug_exception_enter+0xac/0xe8 [ 329.629622] softirqs last enabled at (1608): [<ffff8000100818bc>] __do_softirq+0x4c4/0x578 [ 329.638005] softirqs last disabled at (1561): [<ffff80001010b6ac>] irq_exit+0x144/0x150 [ 329.646035] ---[ end trace bac6584738d9306f ]---
Metadata: --------------- git branch: master git repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git git describe: v5.6-rc5 kernel-config: http://snapshots.linaro.org/openembedded/lkft/lkft/sumo/intel-corei7-64/lkft...
Full test log, https://lkft.validation.linaro.org/scheduler/job/1273667#L6591 https://lkft.validation.linaro.org/scheduler/job/1273569#L6222 https://lkft.validation.linaro.org/scheduler/job/1273548#L6126 https://lkft.validation.linaro.org/scheduler/job/1273596#L4687