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

Melissa Wen mwen at igalia.com
Mon Aug 15 10:55:42 UTC 2022 

On 08/14, Maíra Canal wrote:
> Hi Mikhail
> 
> Looks like this use-after-free problem was introduced on
> 90af0ca047f3049c4b46e902f432ad6ef1e2ded6. Checking this patch it seems
> like: if amdgpu_cs_vm_handling return r != 0, then it will unlock
> bo_list_mutex inside the function amdgpu_cs_vm_handling and again on
> amdgpu_cs_parser_fini.
> 
> Maybe the following patch will help:
> 
> ---
> From 71d718c0f53a334bb59bcd5dabd29bbe92c724af Mon Sep 17 00:00:00 2001
> From: =?UTF-8?q?Ma=C3=ADra=20Canal?= <mairacanal at riseup.net>
> Date: Sun, 14 Aug 2022 21:12:24 -0300
> Subject: [PATCH] drm/amdgpu: Fix use-after-free on amdgpu_bo_list mutex
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
> 
> Fixes: 90af0ca047f3 ("drm/amdgpu: Protect the amdgpu_bo_list list with a
> mutex v2")
> Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov at gmail.com>
> Signed-off-by: Maíra Canal <mairacanal at riseup.net>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> index d8f1335bc68f..a7fce7b14321 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> @@ -837,17 +837,14 @@ static int amdgpu_cs_vm_handling(struct
> amdgpu_cs_parser *p)
>  			continue;
> 
>  		r = amdgpu_vm_bo_update(adev, bo_va, false);
> -		if (r) {
> -			mutex_unlock(&p->bo_list->bo_list_mutex);
> +		if (r)
>  			return r;
> -		}
> 
>  		r = amdgpu_sync_fence(&p->job->sync, bo_va->last_pt_update);
> -		if (r) {
> -			mutex_unlock(&p->bo_list->bo_list_mutex);
> +		if (r)
>  			return r;
> -		}
>  	}
> +	mutex_unlock(&p->bo_list->bo_list_mutex);

I think we don't need to unlock the bo_list_mutex here. If return != 0
amdgpu_cs_parser_fini() will unlock it; otherwise, amdgpu_cs_submit()
unlocks it in the end.

BR,

Melissa
> 
>  	r = amdgpu_vm_handle_moved(adev, vm);
>  	if (r)
> -- 
> 2.37.1
> ---
> Best Regards,
> - Maíra Canal
> 
> On 8/14/22 18:11, Mikhail Gavrilov wrote:
> > Hi folks.
> > Joined testing 5.20 today (7ebfc85e2cd7).
> > I encountered a frequently GPU freeze, after which a message appears
> > in the kernel logs:
> > [ 220.280990] ------------[ cut here ]------------
> > [ 220.281000] refcount_t: underflow; use-after-free.
> > [ 220.281019] WARNING: CPU: 1 PID: 3746 at lib/refcount.c:28
> > refcount_warn_saturate+0xba/0x110
> > [ 220.281029] 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 snd_seq_midi snd_seq_midi_event vfat intel_rapl_msr
> > fat intel_rapl_common snd_hda_codec_realtek mt76x2u
> > snd_hda_codec_generic snd_hda_codec_hdmi mt76x2_common iwlmvm
> > mt76x02_usb edac_mce_amd mt76_usb snd_hda_intel snd_intel_dspcfg
> > mt76x02_lib snd_intel_sdw_acpi snd_usb_audio snd_hda_codec mt76
> > kvm_amd uvcvideo mac80211 snd_hda_core btusb eeepc_wmi snd_usbmidi_lib
> > videobuf2_vmalloc videobuf2_memops kvm btrtl snd_rawmidi asus_wmi
> > snd_hwdep videobuf2_v4l2 btbcm iwlwifi ledtrig_audio libarc4 btintel
> > snd_seq videobuf2_common sparse_keymap btmtk irqbypass videodev
> > snd_seq_device joydev xpad iwlmei platform_profile bluetooth
> > ff_memless snd_pcm mc rapl
> > [ 220.281185] video snd_timer cfg80211 wmi_bmof snd pcspkr soundcore
> > k10temp i2c_piix4 rfkill mei asus_ec_sensors acpi_cpufreq zram
> > hid_logitech_hidpp amdgpu igb dca drm_ttm_helper ttm crct10dif_pclmul
> > iommu_v2 crc32_pclmul gpu_sched crc32c_intel ucsi_ccg drm_buddy nvme
> > typec_ucsi ghash_clmulni_intel drm_display_helper ccp nvme_core typec
> > sp5100_tco cec wmi ip6_tables ip_tables fuse
> > [ 220.281258] 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 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 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 amd64_edac():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 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 amd64_edac():1 pcc_cpufreq():1
> > amd64_edac():1 pcc_cpufreq():1 pcc_cpufreq():1 pcc_cpufreq():1
> > [ 220.281388] pcc_cpufreq():1 fjes():1 pcc_cpufreq():1 fjes():1
> > fjes():1 fjes():1 fjes():1 fjes():1 fjes():1 fjes():1
> > [ 220.281415] CPU: 1 PID: 3746 Comm: chrome:cs0 Tainted: G W L -------
> > --- 5.20.0-0.rc0.20220812git7ebfc85e2cd7.10.fc38.x86_64 #1
> > [ 220.281421] Hardware name: System manufacturer System Product
> > Name/ROG STRIX X570-I GAMING, BIOS 4403 04/27/2022
> > [ 220.281426] RIP: 0010:refcount_warn_saturate+0xba/0x110
> > [ 220.281431] Code: 01 01 e8 79 4a 6f 00 0f 0b e9 42 47 a5 00 80 3d de
> > 7e be 01 00 75 85 48 c7 c7 f8 98 8e 98 c6 05 ce 7e be 01 01 e8 56 4a
> > 6f 00 <0f> 0b e9 1f 47 a5 00 80 3d b9 7e be 01 00 0f 85 5e ff ff ff 48
> > c7
> > [ 220.281437] RSP: 0018:ffffb4b0d18d7a80 EFLAGS: 00010282
> > [ 220.281443] RAX: 0000000000000026 RBX: 0000000000000003 RCX: 0000000000000000
> > [ 220.281448] RDX: 0000000000000001 RSI: ffffffff988d06dc RDI: 00000000ffffffff
> > [ 220.281452] RBP: 00000000ffffffff R08: 0000000000000000 R09: ffffb4b0d18d7930
> > [ 220.281457] R10: 0000000000000003 R11: ffffa0672e2fffe8 R12: ffffa058ca360400
> > [ 220.281461] R13: ffffa05846c50a18 R14: 00000000fffffe00 R15: 0000000000000003
> > [ 220.281465] FS: 00007f82683e06c0(0000) GS:ffffa066e2e00000(0000)
> > knlGS:0000000000000000
> > [ 220.281470] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [ 220.281475] CR2: 00003590005cc000 CR3: 00000001fca46000 CR4: 0000000000350ee0
> > [ 220.281480] Call Trace:
> > [ 220.281485] <TASK>
> > [ 220.281490] amdgpu_cs_ioctl+0x4e2/0x2070 [amdgpu]
> > [ 220.281806] ? amdgpu_cs_find_mapping+0xe0/0xe0 [amdgpu]
> > [ 220.282028] drm_ioctl_kernel+0xa4/0x150
> > [ 220.282043] drm_ioctl+0x21f/0x420
> > [ 220.282053] ? amdgpu_cs_find_mapping+0xe0/0xe0 [amdgpu]
> > [ 220.282275] ? lock_release+0x14f/0x460
> > [ 220.282282] ? _raw_spin_unlock_irqrestore+0x30/0x60
> > [ 220.282290] ? _raw_spin_unlock_irqrestore+0x30/0x60
> > [ 220.282297] ? lockdep_hardirqs_on+0x7d/0x100
> > [ 220.282305] ? _raw_spin_unlock_irqrestore+0x40/0x60
> > [ 220.282317] amdgpu_drm_ioctl+0x4a/0x80 [amdgpu]
> > [ 220.282534] __x64_sys_ioctl+0x90/0xd0
> > [ 220.282545] do_syscall_64+0x5b/0x80
> > [ 220.282551] ? futex_wake+0x6c/0x150
> > [ 220.282568] ? lock_is_held_type+0xe8/0x140
> > [ 220.282580] ? do_syscall_64+0x67/0x80
> > [ 220.282585] ? lockdep_hardirqs_on+0x7d/0x100
> > [ 220.282592] ? do_syscall_64+0x67/0x80
> > [ 220.282597] ? do_syscall_64+0x67/0x80
> > [ 220.282602] ? lockdep_hardirqs_on+0x7d/0x100
> > [ 220.282609] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> > [ 220.282616] RIP: 0033:0x7f8282a4f8bf
> > [ 220.282639] Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10
> > 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00
> > 0f 05 <89> c2 3d 00 f0 ff ff 77 18 48 8b 44 24 18 64 48 2b 04 25 28 00
> > 00
> > [ 220.282644] RSP: 002b:00007f82683df410 EFLAGS: 00000246 ORIG_RAX:
> > 0000000000000010
> > [ 220.282651] RAX: ffffffffffffffda RBX: 00007f82683df588 RCX: 00007f8282a4f8bf
> > [ 220.282655] RDX: 00007f82683df4d0 RSI: 00000000c0186444 RDI: 0000000000000018
> > [ 220.282659] RBP: 00007f82683df4d0 R08: 00007f82683df5e0 R09: 00007f82683df4b0
> > [ 220.282663] R10: 00001d04000a0600 R11: 0000000000000246 R12: 00000000c0186444
> > [ 220.282667] R13: 0000000000000018 R14: 00007f82683df588 R15: 0000000000000003
> > [ 220.282689] </TASK>
> > [ 220.282693] irq event stamp: 6232311
> > [ 220.282697] hardirqs last enabled at (6232319): [<ffffffff9718cd7e>]
> > __up_console_sem+0x5e/0x70
> > [ 220.282704] hardirqs last disabled at (6232326):
> > [<ffffffff9718cd63>] __up_console_sem+0x43/0x70
> > [ 220.282709] softirqs last enabled at (6232072): [<ffffffff970ff669>]
> > __irq_exit_rcu+0xf9/0x170
> > [ 220.282716] softirqs last disabled at (6232061):
> > [<ffffffff970ff669>] __irq_exit_rcu+0xf9/0x170
> > [ 220.282722] ---[ end trace 0000000000000000 ]---
> > 
> > 
> > Full kernel log is here:
> > https://pastebin.com/gn01DVxE
> > 
> > My GPU hardware is AMD Radeon 6900XT.
> > 
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