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

[Mikhail Gavrilov]

On Wed, Aug 17, 2022 at 11:43 PM Maíra Canal <mairacanal@xxxxxxxxxx> wrote:
>
> Hi Mikhail,
>
> Looks like 45ecaea738830b9d521c93520c8f201359dcbd95 ("drm/sched: Partial
> revert of 'drm/sched: Keep s_fence->parent pointer'") introduced the
> error. Try reverting it and check if the use-after-free still happens.

Thanks, but unfortunately, this did not lead to the expected result.
Again happens use-after-free in an incomprehensible context.
>From the new: added warning "suspicious RCU usage" but it looks like
it is completely not related to the use-after-free issue.

[ 215.434115] ------------[ cut here ]------------
[ 215.434184] refcount_t: underflow; use-after-free.
[ 215.434204] WARNING: CPU: 7 PID: 1258 at lib/refcount.c:28
refcount_warn_saturate+0xba/0x110
[ 215.434214] Modules linked in: uinput rfcomm snd_seq_dummy
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
intel_rapl_msr intel_rapl_common snd_hda_codec_realtek vfat
snd_hda_codec_generic snd_hda_codec_hdmi mt76x2u fat mt76x2_common
snd_hda_intel mt76x02_usb snd_intel_dspcfg snd_intel_sdw_acpi mt76_usb
iwlmvm edac_mce_amd snd_usb_audio snd_hda_codec mt76x02_lib
snd_hda_core snd_usbmidi_lib snd_hwdep snd_rawmidi uvcvideo mt76
kvm_amd snd_seq videobuf2_vmalloc videobuf2_memops snd_seq_device
mac80211 videobuf2_v4l2 videobuf2_common kvm btusb iwlwifi snd_pcm
btrtl videodev libarc4 eeepc_wmi btbcm asus_wmi iwlmei btintel
ledtrig_audio xpad irqbypass sparse_keymap btmtk platform_profile
joydev
[ 215.434436] hid_logitech_hidpp rapl ff_memless mc snd_timer
bluetooth cfg80211 video pcspkr wmi_bmof snd soundcore k10temp
i2c_piix4 rfkill mei asus_ec_sensors acpi_cpufreq zram amdgpu
drm_ttm_helper ttm iommu_v2 ucsi_ccg gpu_sched crct10dif_pclmul
crc32_pclmul typec_ucsi drm_buddy crc32c_intel ghash_clmulni_intel ccp
igb sp5100_tco typec drm_display_helper nvme dca nvme_core cec wmi
ip6_tables ip_tables fuse
[ 215.434528] 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
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 amd64_edac():1 pcc_cpufreq():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
amd64_edac():1 pcc_cpufreq():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
amd64_edac():1 pcc_cpufreq():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 pcc_cpufreq():1 amd64_edac():1
pcc_cpufreq():1 amd64_edac():1 pcc_cpufreq():1 pcc_cpufreq():1
pcc_cpufreq():1 pcc_cpufreq():1 pcc_cpufreq():1 fjes():1
[ 215.434672] pcc_cpufreq():1 fjes():1 pcc_cpufreq():1 fjes():1
pcc_cpufreq():1 fjes():1 fjes():1 fjes():1 fjes():1 fjes():1
[ 215.434702] CPU: 7 PID: 1258 Comm: kworker/7:3 Tainted: G W L
------- --- 6.0.0-0.rc1.20220817git3cc40a443a04.14.fc38.x86_64 #1
[ 215.434709] Hardware name: System manufacturer System Product
Name/ROG STRIX X570-I GAMING, BIOS 4403 04/27/2022
[ 215.434715] Workqueue: events drm_sched_entity_kill_jobs_work [gpu_sched]
[ 215.434728] RIP: 0010:refcount_warn_saturate+0xba/0x110
[ 215.434734] Code: 01 01 e8 59 59 6f 00 0f 0b e9 22 46 a5 00 80 3d be
7d be 01 00 75 85 48 c7 c7 c0 99 8e 92 c6 05 ae 7d be 01 01 e8 36 59
6f 00 <0f> 0b e9 ff 45 a5 00 80 3d 99 7d be 01 00 0f 85 5e ff ff ff 48
c7
[ 215.434740] RSP: 0018:ffff9ccb0237fe60 EFLAGS: 00010286
[ 215.434747] RAX: 0000000000000026 RBX: ffff8d531f6f2828 RCX: 0000000000000000
[ 215.434753] RDX: 0000000000000001 RSI: ffffffff928d07a4 RDI: 00000000ffffffff
[ 215.434757] RBP: ffff8d61e47f5600 R08: 0000000000000000 R09: ffff9ccb0237fd10
[ 215.434762] R10: 0000000000000003 R11: ffff8d622e2fffe8 R12: ffff8d61e47fc800
[ 215.434767] R13: ffff8d5313e95500 R14: ffff8d61e47fc805 R15: ffff8d531f6f2830
[ 215.434772] FS: 0000000000000000(0000) GS:ffff8d61e4600000(0000)
knlGS:0000000000000000
[ 215.434777] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 215.434782] CR2: 00007f0c8b815048 CR3: 00000001ab0e8000 CR4: 0000000000350ee0
[ 215.434788] Call Trace:
[ 215.434792] <TASK>
[ 215.434797] process_one_work+0x2a0/0x600
[ 215.434819] worker_thread+0x4f/0x3a0
[ 215.434830] ? process_one_work+0x600/0x600
[ 215.434836] kthread+0xf5/0x120
[ 215.434842] ? kthread_complete_and_exit+0x20/0x20
[ 215.434854] ret_from_fork+0x22/0x30
[ 215.434881] </TASK>
[ 215.434885] irq event stamp: 134873
[ 215.434890] hardirqs last enabled at (134881): [<ffffffff9118ce7e>]
__up_console_sem+0x5e/0x70
[ 215.434897] hardirqs last disabled at (134888): [<ffffffff9118ce63>]
__up_console_sem+0x43/0x70
[ 215.434903] softirqs last enabled at (131264): [<ffffffff910ff769>]
__irq_exit_rcu+0xf9/0x170
[ 215.434910] softirqs last disabled at (131257): [<ffffffff910ff769>]
__irq_exit_rcu+0xf9/0x170
[ 215.434917] ---[ end trace 0000000000000000 ]---

Full kerner log: https://pastebin.com/qED477Pz

-- 
Best Regards,
Mike Gavrilov.