Re: WARNING: at refcount.c:190 refcount_sub_and_test_checked+0xac/0xc8 - refcount_t: underflow; use-after-free.

[Christian Brauner]

On March 11, 2020 8:52:16 AM GMT+01:00, Naresh Kamboju <naresh.kamboju@xxxxxxxxxx> wrote:
>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/linux-mainline/2518/config
>
>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

Thanks, I'll take a look in a little bit.