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

["Maíra Canal" <mairacanal@riseup.net>]

On 8/17/22 17:57, Mikhail Gavrilov wrote:
> On Wed, Aug 17, 2022 at 11:43 PM Maíra Canal <mairacanal@riseup.net> 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.
> 

Hi Mikhail,

Could you please specify the steps to reproduce this use-after-free? I
will try to reproduce it on the RX5700 XT and bisect the issue.

Best Regards,
- Maíra Canal

> [ 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
>