Re: [BUG][5.20] refcount_t: underflow; use-after-free

[Mikhail Gavrilov]

On Mon, Aug 15, 2022 at 3:37 PM Mikhail Gavrilov
<mikhail.v.gavrilov@xxxxxxxxx> wrote:
>
> Thanks, I tested this patch.
> But with this patch use-after-free problem happening in another place:

Does anyone have an idea why the second use-after-free happened?
>From the trace I don't understand which code is related.
I don't quite understand what the "Workqueue" entry in the trace means.

[ 408.358737] ------------[ cut here ]------------
[ 408.358743] refcount_t: underflow; use-after-free.
[ 408.358760] WARNING: CPU: 9 PID: 62 at lib/refcount.c:28
refcount_warn_saturate+0xba/0x110
[ 408.358769] Modules linked in: uinput snd_seq_dummy rfcomm
snd_hrtimer nft_objref nf_conntrack_netbios_ns nf_conntrack_broadcast
nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet
nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat
nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set nf_tables nfnetlink
qrtr bnep sunrpc binfmt_misc snd_seq_midi snd_seq_midi_event mt76x2u
mt76x2_common snd_hda_codec_realtek mt76x02_usb snd_hda_codec_generic
iwlmvm snd_hda_codec_hdmi mt76_usb intel_rapl_msr snd_hda_intel
mt76x02_lib intel_rapl_common snd_intel_dspcfg snd_intel_sdw_acpi mt76
snd_hda_codec vfat fat snd_usb_audio snd_hda_core edac_mce_amd
mac80211 snd_usbmidi_lib snd_hwdep snd_rawmidi mc snd_seq btusb
kvm_amd iwlwifi snd_seq_device btrtl btbcm libarc4 btintel eeepc_wmi
snd_pcm iwlmei kvm btmtk asus_wmi ledtrig_audio irqbypass joydev
snd_timer sparse_keymap bluetooth platform_profile rapl cfg80211 snd
video wmi_bmof soundcore i2c_piix4 k10temp rfkill mei
[ 408.358853] asus_ec_sensors acpi_cpufreq zram hid_logitech_hidpp
amdgpu igb dca drm_ttm_helper ttm iommu_v2 crct10dif_pclmul gpu_sched
crc32_pclmul ucsi_ccg crc32c_intel drm_buddy nvme typec_ucsi
drm_display_helper ghash_clmulni_intel ccp typec nvme_core sp5100_tco
cec wmi ip6_tables ip_tables fuse
[ 408.358880] Unloaded tainted modules: amd64_edac():1 amd64_edac():1
amd64_edac():1 amd64_edac():1 amd64_edac():1 amd64_edac():1
amd64_edac():1 amd64_edac():1 amd64_edac():1 amd64_edac():1
pcc_cpufreq():1 amd64_edac():1 pcc_cpufreq():1 pcc_cpufreq():1
amd64_edac():1 amd64_edac():1 pcc_cpufreq():1 amd64_edac():1
pcc_cpufreq():1 amd64_edac():1 pcc_cpufreq():1 amd64_edac():1
pcc_cpufreq():1 pcc_cpufreq():1 amd64_edac():1 pcc_cpufreq():1
amd64_edac():1 pcc_cpufreq():1 amd64_edac():1 pcc_cpufreq():1
pcc_cpufreq():1 amd64_edac():1 amd64_edac():1 pcc_cpufreq():1
pcc_cpufreq():1 amd64_edac():1 pcc_cpufreq():1 amd64_edac():1
pcc_cpufreq():1 amd64_edac():1 pcc_cpufreq():1 pcc_cpufreq():1
amd64_edac():1 pcc_cpufreq():1 amd64_edac():1 pcc_cpufreq():1
amd64_edac():1 pcc_cpufreq():1 pcc_cpufreq():1 amd64_edac():1
pcc_cpufreq():1 amd64_edac():1 amd64_edac():1 pcc_cpufreq():1
amd64_edac():1 pcc_cpufreq():1 amd64_edac():1 pcc_cpufreq():1
pcc_cpufreq():1 pcc_cpufreq():1 fjes():1 pcc_cpufreq():1 fjes():1
[ 408.358953] pcc_cpufreq():1 pcc_cpufreq():1 fjes():1 pcc_cpufreq():1
fjes():1 fjes():1 fjes():1 fjes():1 fjes():1
[ 408.358967] CPU: 9 PID: 62 Comm: kworker/9:0 Tainted: G W L -------
--- 6.0.0-0.rc1.13.fc38.x86_64+debug #1
[ 408.358971] Hardware name: System manufacturer System Product
Name/ROG STRIX X570-I GAMING, BIOS 4403 04/27/2022
[ 408.358974] Workqueue: events drm_sched_entity_kill_jobs_work [gpu_sched]
[ 408.358982] RIP: 0010:refcount_warn_saturate+0xba/0x110
[ 408.358987] Code: 01 01 e8 d9 59 6f 00 0f 0b e9 a2 46 a5 00 80 3d 3e
7e be 01 00 75 85 48 c7 c7 70 99 8e 92 c6 05 2e 7e be 01 01 e8 b6 59
6f 00 <0f> 0b e9 7f 46 a5 00 80 3d 19 7e be 01 00 0f 85 5e ff ff ff 48
c7
[ 408.358990] RSP: 0018:ffffb124003efe60 EFLAGS: 00010286
[ 408.358994] RAX: 0000000000000026 RBX: ffff9987a025d428 RCX: 0000000000000000
[ 408.358997] RDX: 0000000000000001 RSI: ffffffff928d0754 RDI: 00000000ffffffff
[ 408.358999] RBP: ffff9994e4ff5600 R08: 0000000000000000 R09: ffffb124003efd10
[ 408.359001] R10: 0000000000000003 R11: ffff99952e2fffe8 R12: ffff9994e4ffc800
[ 408.359004] R13: ffff998600228cc0 R14: ffff9994e4ffc805 R15: ffff9987a025d430
[ 408.359006] FS: 0000000000000000(0000) GS:ffff9994e4e00000(0000)
knlGS:0000000000000000
[ 408.359009] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 408.359012] CR2: 000027ac39e78000 CR3: 00000001a66d8000 CR4: 0000000000350ee0
[ 408.359015] Call Trace:
[ 408.359017] <TASK>
[ 408.359020] process_one_work+0x2a0/0x600
[ 408.359032] worker_thread+0x4f/0x3a0
[ 408.359036] ? process_one_work+0x600/0x600
[ 408.359039] kthread+0xf5/0x120
[ 408.359044] ? kthread_complete_and_exit+0x20/0x20
[ 408.359049] ret_from_fork+0x22/0x30
[ 408.359061] </TASK>
[ 408.359063] irq event stamp: 5468
[ 408.359064] hardirqs last enabled at (5467): [<ffffffff91f2b9e4>]
_raw_spin_unlock_irq+0x24/0x50
[ 408.359071] hardirqs last disabled at (5468): [<ffffffff91f22d8c>]
__schedule+0xe2c/0x16d0
[ 408.359076] softirqs last enabled at (2482): [<ffffffff917acc28>]
rht_deferred_worker+0x708/0xc00
[ 408.359079] softirqs last disabled at (2480): [<ffffffff917ac717>]
rht_deferred_worker+0x1f7/0xc00
[ 408.359082] ---[ end trace 0000000000000000 ]---


Full kernel log is here: https://pastebin.com/Lam9CRLV

-- 
Best Regards,
Mike Gavrilov.