From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from fanzine2.igalia.com (fanzine2.igalia.com [213.97.179.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 56AFA28C009; Thu, 14 Aug 2025 10:42:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.97.179.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755168158; cv=none; b=k0S/wV+oU8kA3Lf17hVJvmZJe437Kav5kDG+8l4PHdST+rj9QETXUTDZNNJXhw4N581j0VCCfVinl5XGozwQAbGt1xvcM9oB1+ET3t/OmfivwuhxZ4f+XIPelurpoyDrjhyQHINq1zco2rdHWZ5F4a90tUahFp1qaox8qoWgNBU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755168158; c=relaxed/simple; bh=oqCX9autwTY+IiM9hph/igZfAA0SN1ef2vNeqiN5K/Y=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=MZC+u3SuhAGQ3uBeE+ObruNXEe7k69AHTcUw1hjnmO7reeBvfNTEgXGsQyFp6ZWNGUoKh82/9QShbJvxH5VJKwxJnOqVwXGx9g5aaamVJc+GOhZf+VHf5QyPLwwsY1P2ERzxMXKdh5lhL7iEFpLfrPtJgiwjsi82yAJrMtBfjwU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com; spf=pass smtp.mailfrom=igalia.com; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b=WCJmN5yH; arc=none smtp.client-ip=213.97.179.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=igalia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b="WCJmN5yH" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:From: References:Cc:To:Subject:MIME-Version:Date:Message-ID:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=lzNkoTK8jNRy8Sns5LfCBbkMbmoCTQMDRBvRCKy89e4=; b=WCJmN5yHWDCXlRCOpg9eArOyxC ycSkOvgT1DPTMGIYH/uwojw/t+tQ1orLwkHbZuauaKVWHW3/J1Uxb64Nv23xApB+MWiekDbLnUOFk 7D6tYsx8BXxLw9X0ws4b5LkHI8tkQC4HvU32D8OI2CdDag0E/kFJnfZffQ1gQhBGgcfG8Nwufu9Ld ymyuIHxaVF9yzR91FTOpWnmSdvnIVfgZ2fXT2IilZaODdii0PH8rYiOzvLVHfJQB/pFGwfsz1ipH9 dvwvMi6LuE5xmxq3iTLUfTsbLCNWFT47ffUhDs8VPs2XayYkls39r0fOh0qtazSWhjXLY9TptqnBy q4zpUGwQ==; Received: from [84.66.36.92] (helo=[192.168.0.101]) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_128_GCM:128) (Exim) id 1umVPI-00E4ky-6l; Thu, 14 Aug 2025 12:42:04 +0200 Message-ID: <67c6a43a-a18b-4b5c-bb43-ba3aea2df05f@igalia.com> Date: Thu, 14 Aug 2025 11:42:02 +0100 Precedence: bulk X-Mailing-List: linux-kernel-mentees@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drm/sched: Prevent stopped entities from being added to the run queue. To: phasta@kernel.org, James Flowers , matthew.brost@intel.com, dakr@kernel.org, ckoenig.leichtzumerken@gmail.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch, skhan@linuxfoundation.org Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linux.dev References: <20250720235748.2798-1-bold.zone2373@fastmail.com> <66a14b005fa3dc874f4f3261b93901af1292bde9.camel@mailbox.org> Content-Language: en-GB From: Tvrtko Ursulin In-Reply-To: <66a14b005fa3dc874f4f3261b93901af1292bde9.camel@mailbox.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 21/07/2025 08:52, Philipp Stanner wrote: > +Cc Tvrtko, who's currently reworking FIFO and RR. > > On Sun, 2025-07-20 at 16:56 -0700, James Flowers wrote: >> Fixes an issue where entities are added to the run queue in >> drm_sched_rq_update_fifo_locked after being killed, causing a >> slab-use-after-free error. >> >> Signed-off-by: James Flowers >> --- >> This issue was detected by syzkaller running on a Steam Deck OLED. >> Unfortunately I don't have a reproducer for it. I've > > Well, now that's kind of an issue – if you don't have a reproducer, how > can you know that your patch is correct? How can we? > > It would certainly be good to know what the fuzz testing framework > does. > >> included the KASAN reports below: > > > Anyways, KASAN reports look interesting. But those might be many > different issues. Again, would be good to know what the fuzzer has been > testing. Can you maybe split this fuzz test into sub-tests? I suspsect > those might be different faults. > > > Anyways, taking a first look… > > >> >> ================================================================== >> BUG: KASAN: slab-use-after-free in rb_next+0xda/0x160 lib/rbtree.c:505 >> Read of size 8 at addr ffff8881805085e0 by task kworker/u32:12/192 >> CPU: 3 UID: 0 PID: 192 Comm: kworker/u32:12 Not tainted 6.14.0-flowejam-+ #1 >> Hardware name: Valve Galileo/Galileo, BIOS F7G0112 08/01/2024 >> Workqueue: sdma0 drm_sched_run_job_work [gpu_sched] >> Call Trace: >>   >>  __dump_stack lib/dump_stack.c:94 [inline] >>  dump_stack_lvl+0xd2/0x130 lib/dump_stack.c:120 >>  print_address_description.constprop.0+0x88/0x380 mm/kasan/report.c:408 >>  print_report+0xfc/0x1ff mm/kasan/report.c:521 >>  kasan_report+0xdd/0x1b0 mm/kasan/report.c:634 >>  rb_next+0xda/0x160 lib/rbtree.c:505 >>  drm_sched_rq_select_entity_fifo drivers/gpu/drm/scheduler/sched_main.c:332 [inline] [gpu_sched] >>  drm_sched_select_entity+0x497/0x720 drivers/gpu/drm/scheduler/sched_main.c:1081 [gpu_sched] >>  drm_sched_run_job_work+0x2e/0x710 drivers/gpu/drm/scheduler/sched_main.c:1206 [gpu_sched] >>  process_one_work+0x9c0/0x17e0 kernel/workqueue.c:3238 >>  process_scheduled_works kernel/workqueue.c:3319 [inline] >>  worker_thread+0x734/0x1060 kernel/workqueue.c:3400 >>  kthread+0x3fd/0x810 kernel/kthread.c:464 >>  ret_from_fork+0x53/0x80 arch/x86/kernel/process.c:148 >>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 >>   >> Allocated by task 73472: >>  kasan_save_stack+0x30/0x50 mm/kasan/common.c:47 >>  kasan_save_track+0x14/0x30 mm/kasan/common.c:68 >>  poison_kmalloc_redzone mm/kasan/common.c:377 [inline] >>  __kasan_kmalloc+0x9a/0xb0 mm/kasan/common.c:394 >>  kmalloc_noprof include/linux/slab.h:901 [inline] [amdgpu] >>  kzalloc_noprof include/linux/slab.h:1037 [inline] [amdgpu] >>  amdgpu_driver_open_kms+0x151/0x660 drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c:1402 [amdgpu] >>  drm_file_alloc+0x5d0/0xa00 drivers/gpu/drm/drm_file.c:171 >>  drm_open_helper+0x1fe/0x540 drivers/gpu/drm/drm_file.c:323 >>  drm_open+0x1a7/0x400 drivers/gpu/drm/drm_file.c:376 >>  drm_stub_open+0x21a/0x390 drivers/gpu/drm/drm_drv.c:1149 >>  chrdev_open+0x23b/0x6b0 fs/char_dev.c:414 >>  do_dentry_open+0x743/0x1bf0 fs/open.c:956 >>  vfs_open+0x87/0x3f0 fs/open.c:1086 >>  do_open+0x72f/0xf80 fs/namei.c:3830 >>  path_openat+0x2ec/0x770 fs/namei.c:3989 >>  do_filp_open+0x1ff/0x420 fs/namei.c:4016 >>  do_sys_openat2+0x181/0x1e0 fs/open.c:1428 >>  do_sys_open fs/open.c:1443 [inline] >>  __do_sys_openat fs/open.c:1459 [inline] >>  __se_sys_openat fs/open.c:1454 [inline] >>  __x64_sys_openat+0x149/0x210 fs/open.c:1454 >>  do_syscall_x64 arch/x86/entry/common.c:52 [inline] >>  do_syscall_64+0x92/0x180 arch/x86/entry/common.c:83 >>  entry_SYSCALL_64_after_hwframe+0x76/0x7e >> Freed by task 73472: >>  kasan_save_stack+0x30/0x50 mm/kasan/common.c:47 >>  kasan_save_track+0x14/0x30 mm/kasan/common.c:68 >>  kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:576 >>  poison_slab_object mm/kasan/common.c:247 [inline] >>  __kasan_slab_free+0x52/0x70 mm/kasan/common.c:264 >>  kasan_slab_free include/linux/kasan.h:233 [inline] >>  slab_free_hook mm/slub.c:2353 [inline] >>  slab_free mm/slub.c:4609 [inline] >>  kfree+0x14f/0x4d0 mm/slub.c:4757 >>  amdgpu_driver_postclose_kms+0x43d/0x6b0 drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c:1538 [amdgpu] >>  drm_file_free.part.0+0x72d/0xbc0 drivers/gpu/drm/drm_file.c:255 >>  drm_file_free drivers/gpu/drm/drm_file.c:228 [inline] >>  drm_close_helper.isra.0+0x197/0x230 drivers/gpu/drm/drm_file.c:278 >>  drm_release+0x1b0/0x3d0 drivers/gpu/drm/drm_file.c:426 >>  __fput+0x402/0xb50 fs/file_table.c:464 >>  task_work_run+0x155/0x250 kernel/task_work.c:227 >>  get_signal+0x1be/0x19d0 kernel/signal.c:2809 >>  arch_do_signal_or_restart+0x96/0x3a0 arch/x86/kernel/signal.c:337 >>  exit_to_user_mode_loop kernel/entry/common.c:111 [inline] >>  exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] >>  __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] >>  syscall_exit_to_user_mode+0x1fc/0x290 kernel/entry/common.c:218 >>  do_syscall_64+0x9f/0x180 arch/x86/entry/common.c:89 >>  entry_SYSCALL_64_after_hwframe+0x76/0x7e >> The buggy address belongs to the object at ffff888180508000 >> The buggy address is located 1504 bytes inside of >> The buggy address belongs to the physical page: >> page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x180508 >> head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 >> flags: 0x17ffffc0000040(head|node=0|zone=2|lastcpupid=0x1fffff) >> page_type: f5(slab) >> raw: 0017ffffc0000040 ffff888100043180 dead000000000100 dead000000000122 >> raw: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000 >> head: 0017ffffc0000040 ffff888100043180 dead000000000100 dead000000000122 >> head: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000 >> head: 0017ffffc0000003 ffffea0006014201 ffffffffffffffff 0000000000000000 >> head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000 >> page dumped because: kasan: bad access detected >> Memory state around the buggy address: >>  ffff888180508480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>  ffff888180508500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>> ffff888180508580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>                                                        ^ >>  ffff888180508600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>  ffff888180508680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ================================================================== >> ================================================================== >> BUG: KASAN: slab-use-after-free in rb_set_parent_color include/linux/rbtree_augmented.h:191 [inline] >> BUG: KASAN: slab-use-after-free in __rb_erase_augmented include/linux/rbtree_augmented.h:312 [inline] >> BUG: KASAN: slab-use-after-free in rb_erase+0x157c/0x1b10 lib/rbtree.c:443 >> Write of size 8 at addr ffff88816414c5d0 by task syz.2.3004/12376 >> CPU: 7 UID: 65534 PID: 12376 Comm: syz.2.3004 Not tainted 6.14.0-flowejam-+ #1 >> Hardware name: Valve Galileo/Galileo, BIOS F7G0112 08/01/2024 >> Call Trace: >>   >>  __dump_stack lib/dump_stack.c:94 [inline] >>  dump_stack_lvl+0xd2/0x130 lib/dump_stack.c:120 >>  print_address_description.constprop.0+0x88/0x380 mm/kasan/report.c:408 >>  print_report+0xfc/0x1ff mm/kasan/report.c:521 >>  kasan_report+0xdd/0x1b0 mm/kasan/report.c:634 >>  rb_set_parent_color include/linux/rbtree_augmented.h:191 [inline] >>  __rb_erase_augmented include/linux/rbtree_augmented.h:312 [inline] >>  rb_erase+0x157c/0x1b10 lib/rbtree.c:443 >>  rb_erase_cached include/linux/rbtree.h:126 [inline] [gpu_sched] >>  drm_sched_rq_remove_fifo_locked drivers/gpu/drm/scheduler/sched_main.c:154 [inline] [gpu_sched] >>  drm_sched_rq_remove_entity+0x2d3/0x480 drivers/gpu/drm/scheduler/sched_main.c:243 [gpu_sched] >>  drm_sched_entity_kill.part.0+0x82/0x5e0 drivers/gpu/drm/scheduler/sched_entity.c:237 [gpu_sched] >>  drm_sched_entity_kill drivers/gpu/drm/scheduler/sched_entity.c:232 [inline] [gpu_sched] >>  drm_sched_entity_fini+0x4c/0x290 drivers/gpu/drm/scheduler/sched_entity.c:331 [gpu_sched] >>  amdgpu_vm_fini_entities drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c:529 [inline] [amdgpu] >>  amdgpu_vm_fini+0x862/0x1180 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c:2752 [amdgpu] >>  amdgpu_driver_postclose_kms+0x3db/0x6b0 drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c:1526 [amdgpu] >>  drm_file_free.part.0+0x72d/0xbc0 drivers/gpu/drm/drm_file.c:255 >>  drm_file_free drivers/gpu/drm/drm_file.c:228 [inline] >>  drm_close_helper.isra.0+0x197/0x230 drivers/gpu/drm/drm_file.c:278 >>  drm_release+0x1b0/0x3d0 drivers/gpu/drm/drm_file.c:426 >>  __fput+0x402/0xb50 fs/file_table.c:464 >>  task_work_run+0x155/0x250 kernel/task_work.c:227 >>  exit_task_work include/linux/task_work.h:40 [inline] >>  do_exit+0x841/0xf60 kernel/exit.c:938 >>  do_group_exit+0xda/0x2b0 kernel/exit.c:1087 >>  get_signal+0x171f/0x19d0 kernel/signal.c:3036 >>  arch_do_signal_or_restart+0x96/0x3a0 arch/x86/kernel/signal.c:337 >>  exit_to_user_mode_loop kernel/entry/common.c:111 [inline] >>  exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] >>  __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] >>  syscall_exit_to_user_mode+0x1fc/0x290 kernel/entry/common.c:218 >>  do_syscall_64+0x9f/0x180 arch/x86/entry/common.c:89 >>  entry_SYSCALL_64_after_hwframe+0x76/0x7e >> RIP: 0033:0x7f2d90da36ed >> Code: Unable to access opcode bytes at 0x7f2d90da36c3. >> RSP: 002b:00007f2d91b710d8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca >> RAX: 0000000000000000 RBX: 00007f2d90fe6088 RCX: 00007f2d90da36ed >> RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f2d90fe6088 >> RBP: 00007f2d90fe6080 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f2d90fe608c >> R13: 0000000000000000 R14: 0000000000000002 R15: 00007ffc34a67bd0 >>   >> Allocated by task 12381: >>  kasan_save_stack+0x30/0x50 mm/kasan/common.c:47 >>  kasan_save_track+0x14/0x30 mm/kasan/common.c:68 >>  poison_kmalloc_redzone mm/kasan/common.c:377 [inline] >>  __kasan_kmalloc+0x9a/0xb0 mm/kasan/common.c:394 >>  kmalloc_noprof include/linux/slab.h:901 [inline] [amdgpu] >>  kzalloc_noprof include/linux/slab.h:1037 [inline] [amdgpu] >>  amdgpu_driver_open_kms+0x151/0x660 drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c:1402 [amdgpu] >>  drm_file_alloc+0x5d0/0xa00 drivers/gpu/drm/drm_file.c:171 >>  drm_open_helper+0x1fe/0x540 drivers/gpu/drm/drm_file.c:323 >>  drm_open+0x1a7/0x400 drivers/gpu/drm/drm_file.c:376 >>  drm_stub_open+0x21a/0x390 drivers/gpu/drm/drm_drv.c:1149 >>  chrdev_open+0x23b/0x6b0 fs/char_dev.c:414 >>  do_dentry_open+0x743/0x1bf0 fs/open.c:956 >>  vfs_open+0x87/0x3f0 fs/open.c:1086 >>  do_open+0x72f/0xf80 fs/namei.c:3830 >>  path_openat+0x2ec/0x770 fs/namei.c:3989 >>  do_filp_open+0x1ff/0x420 fs/namei.c:4016 >>  do_sys_openat2+0x181/0x1e0 fs/open.c:1428 >>  do_sys_open fs/open.c:1443 [inline] >>  __do_sys_openat fs/open.c:1459 [inline] >>  __se_sys_openat fs/open.c:1454 [inline] >>  __x64_sys_openat+0x149/0x210 fs/open.c:1454 >>  do_syscall_x64 arch/x86/entry/common.c:52 [inline] >>  do_syscall_64+0x92/0x180 arch/x86/entry/common.c:83 >>  entry_SYSCALL_64_after_hwframe+0x76/0x7e >> Freed by task 12381: >>  kasan_save_stack+0x30/0x50 mm/kasan/common.c:47 >>  kasan_save_track+0x14/0x30 mm/kasan/common.c:68 >>  kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:576 >>  poison_slab_object mm/kasan/common.c:247 [inline] >>  __kasan_slab_free+0x52/0x70 mm/kasan/common.c:264 >>  kasan_slab_free include/linux/kasan.h:233 [inline] >>  slab_free_hook mm/slub.c:2353 [inline] >>  slab_free mm/slub.c:4609 [inline] >>  kfree+0x14f/0x4d0 mm/slub.c:4757 >>  amdgpu_driver_postclose_kms+0x43d/0x6b0 drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c:1538 [amdgpu] >>  drm_file_free.part.0+0x72d/0xbc0 drivers/gpu/drm/drm_file.c:255 >>  drm_file_free drivers/gpu/drm/drm_file.c:228 [inline] >>  drm_close_helper.isra.0+0x197/0x230 drivers/gpu/drm/drm_file.c:278 >>  drm_release+0x1b0/0x3d0 drivers/gpu/drm/drm_file.c:426 >>  __fput+0x402/0xb50 fs/file_table.c:464 >>  task_work_run+0x155/0x250 kernel/task_work.c:227 >>  get_signal+0x1be/0x19d0 kernel/signal.c:2809 >>  arch_do_signal_or_restart+0x96/0x3a0 arch/x86/kernel/signal.c:337 >>  exit_to_user_mode_loop kernel/entry/common.c:111 [inline] >>  exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] >>  __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] >>  syscall_exit_to_user_mode+0x1fc/0x290 kernel/entry/common.c:218 >>  do_syscall_64+0x9f/0x180 arch/x86/entry/common.c:89 >>  entry_SYSCALL_64_after_hwframe+0x76/0x7e >> The buggy address belongs to the object at ffff88816414c000 >> The buggy address is located 1488 bytes inside of >> The buggy address belongs to the physical page: >> page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x164148 >> head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 >> flags: 0x17ffffc0000040(head|node=0|zone=2|lastcpupid=0x1fffff) >> page_type: f5(slab) >> raw: 0017ffffc0000040 ffff88810005c8c0 dead000000000122 0000000000000000 >> raw: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000 >> head: 0017ffffc0000040 ffff88810005c8c0 dead000000000122 0000000000000000 >> head: 0000000000000000 0000000080020002 00000000f5000000 0000000000000000 >> head: 0017ffffc0000003 ffffea0005905201 ffffffffffffffff 0000000000000000 >> head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000 >> page dumped because: kasan: bad access detected >> Memory state around the buggy address: >>  ffff88816414c480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>  ffff88816414c500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>> ffff88816414c580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>                                                  ^ >>  ffff88816414c600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>  ffff88816414c680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ================================================================== >> ================================================================== >> BUG: KASAN: slab-use-after-free in __rb_erase_augmented include/linux/rbtree_augmented.h:259 [inline] >> BUG: KASAN: slab-use-after-free in rb_erase+0xf5d/0x1b10 lib/rbtree.c:443 >> Read of size 8 at addr ffff88812ebcc5e0 by task syz.1.814/6553 >> CPU: 0 UID: 65534 PID: 6553 Comm: syz.1.814 Not tainted 6.14.0-flowejam-+ #1 >> Hardware name: Valve Galileo/Galileo, BIOS F7G0112 08/01/2024 >> Call Trace: >>   >>  __dump_stack lib/dump_stack.c:94 [inline] >>  dump_stack_lvl+0xd2/0x130 lib/dump_stack.c:120 >>  print_address_description.constprop.0+0x88/0x380 mm/kasan/report.c:408 >>  print_report+0xfc/0x1ff mm/kasan/report.c:521 >>  kasan_report+0xdd/0x1b0 mm/kasan/report.c:634 >>  __rb_erase_augmented include/linux/rbtree_augmented.h:259 [inline] >>  rb_erase+0xf5d/0x1b10 lib/rbtree.c:443 >>  rb_erase_cached include/linux/rbtree.h:126 [inline] [gpu_sched] >>  drm_sched_rq_remove_fifo_locked drivers/gpu/drm/scheduler/sched_main.c:154 [inline] [gpu_sched] >>  drm_sched_rq_remove_entity+0x2d3/0x480 drivers/gpu/drm/scheduler/sched_main.c:243 [gpu_sched] >>  drm_sched_entity_kill.part.0+0x82/0x5e0 drivers/gpu/drm/scheduler/sched_entity.c:237 [gpu_sched] >>  drm_sched_entity_kill drivers/gpu/drm/scheduler/sched_entity.c:232 [inline] [gpu_sched] >>  drm_sched_entity_fini+0x4c/0x290 drivers/gpu/drm/scheduler/sched_entity.c:331 [gpu_sched] >>  amdgpu_vm_fini_entities drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c:529 [inline] [amdgpu] >>  amdgpu_vm_fini+0x862/0x1180 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c:2752 [amdgpu] >>  amdgpu_driver_postclose_kms+0x3db/0x6b0 drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c:1526 [amdgpu] >>  drm_file_free.part.0+0x72d/0xbc0 drivers/gpu/drm/drm_file.c:255 >>  drm_file_free drivers/gpu/drm/drm_file.c:228 [inline] >>  drm_close_helper.isra.0+0x197/0x230 drivers/gpu/drm/drm_file.c:278 >>  drm_release+0x1b0/0x3d0 drivers/gpu/drm/drm_file.c:426 >>  __fput+0x402/0xb50 fs/file_table.c:464 >>  task_work_run+0x155/0x250 kernel/task_work.c:227 >>  resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] >>  exit_to_user_mode_loop kernel/entry/common.c:114 [inline] >>  exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] >>  __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] >>  syscall_exit_to_user_mode+0x26b/0x290 kernel/entry/common.c:218 >>  do_syscall_64+0x9f/0x180 arch/x86/entry/common.c:89 >>  entry_SYSCALL_64_after_hwframe+0x76/0x7e >> RIP: 0033:0x7fd23eba36ed >> Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48 >> RSP: 002b:00007ffc2943a358 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4 >> RAX: 0000000000000000 RBX: 00007ffc2943a428 RCX: 00007fd23eba36ed >> RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003 >> RBP: 00007fd23ede7ba0 R08: 0000000000000001 R09: 0000000c00000000 >> R10: 00007fd23ea00000 R11: 0000000000000246 R12: 00007fd23ede5fac >> R13: 00007fd23ede5fa0 R14: 0000000000059ad1 R15: 0000000000059a8e >>   >> Allocated by task 6559: >>  kasan_save_stack+0x30/0x50 mm/kasan/common.c:47 >>  kasan_save_track+0x14/0x30 mm/kasan/common.c:68 >>  poison_kmalloc_redzone mm/kasan/common.c:377 [inline] >>  __kasan_kmalloc+0x9a/0xb0 mm/kasan/common.c:394 >>  kmalloc_noprof include/linux/slab.h:901 [inline] [amdgpu] >>  kzalloc_noprof include/linux/slab.h:1037 [inline] [amdgpu] >>  amdgpu_driver_open_kms+0x151/0x660 drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c:1402 [amdgpu] >>  drm_file_alloc+0x5d0/0xa00 drivers/gpu/drm/drm_file.c:171 >>  drm_open_helper+0x1fe/0x540 drivers/gpu/drm/drm_file.c:323 >>  drm_open+0x1a7/0x400 drivers/gpu/drm/drm_file.c:376 >>  drm_stub_open+0x21a/0x390 drivers/gpu/drm/drm_drv.c:1149 >>  chrdev_open+0x23b/0x6b0 fs/char_dev.c:414 >>  do_dentry_open+0x743/0x1bf0 fs/open.c:956 >>  vfs_open+0x87/0x3f0 fs/open.c:1086 >>  do_open+0x72f/0xf80 fs/namei.c:3830 >>  path_openat+0x2ec/0x770 fs/namei.c:3989 >>  do_filp_open+0x1ff/0x420 fs/namei.c:4016 >>  do_sys_openat2+0x181/0x1e0 fs/open.c:1428 >>  do_sys_open fs/open.c:1443 [inline] >>  __do_sys_openat fs/open.c:1459 [inline] >>  __se_sys_openat fs/open.c:1454 [inline] >>  __x64_sys_openat+0x149/0x210 fs/open.c:1454 >>  do_syscall_x64 arch/x86/entry/common.c:52 [inline] >>  do_syscall_64+0x92/0x180 arch/x86/entry/common.c:83 >>  entry_SYSCALL_64_after_hwframe+0x76/0x7e >> Freed by task 6559: >>  kasan_save_stack+0x30/0x50 mm/kasan/common.c:47 >>  kasan_save_track+0x14/0x30 mm/kasan/common.c:68 >>  kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:576 >>  poison_slab_object mm/kasan/common.c:247 [inline] >>  __kasan_slab_free+0x52/0x70 mm/kasan/common.c:264 >>  kasan_slab_free include/linux/kasan.h:233 [inline] >>  slab_free_hook mm/slub.c:2353 [inline] >>  slab_free mm/slub.c:4609 [inline] >>  kfree+0x14f/0x4d0 mm/slub.c:4757 >>  amdgpu_driver_postclose_kms+0x43d/0x6b0 drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c:1538 [amdgpu] >>  drm_file_free.part.0+0x72d/0xbc0 drivers/gpu/drm/drm_file.c:255 >>  drm_file_free drivers/gpu/drm/drm_file.c:228 [inline] >>  drm_close_helper.isra.0+0x197/0x230 drivers/gpu/drm/drm_file.c:278 >>  drm_release+0x1b0/0x3d0 drivers/gpu/drm/drm_file.c:426 >>  __fput+0x402/0xb50 fs/file_table.c:464 >>  task_work_run+0x155/0x250 kernel/task_work.c:227 >>  get_signal+0x1be/0x19d0 kernel/signal.c:2809 >>  arch_do_signal_or_restart+0x96/0x3a0 arch/x86/kernel/signal.c:337 >>  exit_to_user_mode_loop kernel/entry/common.c:111 [inline] >>  exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] >>  __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] >>  syscall_exit_to_user_mode+0x1fc/0x290 kernel/entry/common.c:218 >>  do_syscall_64+0x9f/0x180 arch/x86/entry/common.c:89 >>  entry_SYSCALL_64_after_hwframe+0x76/0x7e >> The buggy address belongs to the object at ffff88812ebcc000 >> The buggy address is located 1504 bytes inside of >> The buggy address belongs to the physical page: >> page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12ebc8 >> head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 >> flags: 0x17ffffc0000040(head|node=0|zone=2|lastcpupid=0x1fffff) >> page_type: f5(slab) >> raw: 0017ffffc0000040 ffff888100058780 dead000000000122 0000000000000000 >> raw: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000 >> head: 0017ffffc0000040 ffff888100058780 dead000000000122 0000000000000000 >> head: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000 >> head: 0017ffffc0000003 ffffea0004baf201 ffffffffffffffff 0000000000000000 >> head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000 >> page dumped because: kasan: bad access detected >> Memory state around the buggy address: >>  ffff88812ebcc480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>  ffff88812ebcc500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>> ffff88812ebcc580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>                                                        ^ >>  ffff88812ebcc600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>  ffff88812ebcc680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ================================================================== >> ================================================================== >> BUG: KASAN: slab-use-after-free in drm_sched_entity_compare_before drivers/gpu/drm/scheduler/sched_main.c:147 [inline] [gpu_sched] >> BUG: KASAN: slab-use-after-free in rb_add_cached include/linux/rbtree.h:174 [inline] [gpu_sched] >> BUG: KASAN: slab-use-after-free in drm_sched_rq_update_fifo_locked+0x47b/0x540 drivers/gpu/drm/scheduler/sched_main.c:175 [gpu_sched] >> Read of size 8 at addr ffff8881208445c8 by task syz.1.49115/146644 >> CPU: 7 UID: 65534 PID: 146644 Comm: syz.1.49115 Not tainted 6.14.0-flowejam-+ #1 >> Hardware name: Valve Galileo/Galileo, BIOS F7G0112 08/01/2024 >> Call Trace: >>   >>  __dump_stack lib/dump_stack.c:94 [inline] >>  dump_stack_lvl+0xd2/0x130 lib/dump_stack.c:120 >>  print_address_description.constprop.0+0x88/0x380 mm/kasan/report.c:408 >>  print_report+0xfc/0x1ff mm/kasan/report.c:521 >>  kasan_report+0xdd/0x1b0 mm/kasan/report.c:634 >>  drm_sched_entity_compare_before drivers/gpu/drm/scheduler/sched_main.c:147 [inline] [gpu_sched] >>  rb_add_cached include/linux/rbtree.h:174 [inline] [gpu_sched] >>  drm_sched_rq_update_fifo_locked+0x47b/0x540 drivers/gpu/drm/scheduler/sched_main.c:175 [gpu_sched] >>  drm_sched_entity_push_job+0x509/0x5d0 drivers/gpu/drm/scheduler/sched_entity.c:623 [gpu_sched] > > This might be a race between entity killing and the push_job. Let's > look at your patch below… > >>  amdgpu_job_submit+0x1a4/0x270 drivers/gpu/drm/amd/amdgpu/amdgpu_job.c:314 [amdgpu] >>  amdgpu_vm_sdma_commit+0x1f9/0x7d0 drivers/gpu/drm/amd/amdgpu/amdgpu_vm_sdma.c:122 [amdgpu] >>  amdgpu_vm_pt_clear+0x540/0x6b0 drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c:422 [amdgpu] >>  amdgpu_vm_init+0x9c2/0x12f0 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c:2609 [amdgpu] >>  amdgpu_driver_open_kms+0x274/0x660 drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c:1418 [amdgpu] >>  drm_file_alloc+0x5d0/0xa00 drivers/gpu/drm/drm_file.c:171 >>  drm_open_helper+0x1fe/0x540 drivers/gpu/drm/drm_file.c:323 >>  drm_open+0x1a7/0x400 drivers/gpu/drm/drm_file.c:376 >>  drm_stub_open+0x21a/0x390 drivers/gpu/drm/drm_drv.c:1149 >>  chrdev_open+0x23b/0x6b0 fs/char_dev.c:414 >>  do_dentry_open+0x743/0x1bf0 fs/open.c:956 >>  vfs_open+0x87/0x3f0 fs/open.c:1086 >>  do_open+0x72f/0xf80 fs/namei.c:3830 >>  path_openat+0x2ec/0x770 fs/namei.c:3989 >>  do_filp_open+0x1ff/0x420 fs/namei.c:4016 >>  do_sys_openat2+0x181/0x1e0 fs/open.c:1428 >>  do_sys_open fs/open.c:1443 [inline] >>  __do_sys_openat fs/open.c:1459 [inline] >>  __se_sys_openat fs/open.c:1454 [inline] >>  __x64_sys_openat+0x149/0x210 fs/open.c:1454 >>  do_syscall_x64 arch/x86/entry/common.c:52 [inline] >>  do_syscall_64+0x92/0x180 arch/x86/entry/common.c:83 >>  entry_SYSCALL_64_after_hwframe+0x76/0x7e >> RIP: 0033:0x7feb303a36ed >> Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48 >> RSP: 002b:00007feb3123c018 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 >> RAX: ffffffffffffffda RBX: 00007feb305e5fa0 RCX: 00007feb303a36ed >> RDX: 0000000000000002 RSI: 0000200000000140 RDI: ffffffffffffff9c >> RBP: 00007feb30447722 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 >> R13: 0000000000000001 R14: 00007feb305e5fa0 R15: 00007ffcfd0a3460 >>   >> Allocated by task 146638: >>  kasan_save_stack+0x30/0x50 mm/kasan/common.c:47 >>  kasan_save_track+0x14/0x30 mm/kasan/common.c:68 >>  poison_kmalloc_redzone mm/kasan/common.c:377 [inline] >>  __kasan_kmalloc+0x9a/0xb0 mm/kasan/common.c:394 >>  kmalloc_noprof include/linux/slab.h:901 [inline] [amdgpu] >>  kzalloc_noprof include/linux/slab.h:1037 [inline] [amdgpu] >>  amdgpu_driver_open_kms+0x151/0x660 drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c:1402 [amdgpu] >>  drm_file_alloc+0x5d0/0xa00 drivers/gpu/drm/drm_file.c:171 >>  drm_open_helper+0x1fe/0x540 drivers/gpu/drm/drm_file.c:323 >>  drm_open+0x1a7/0x400 drivers/gpu/drm/drm_file.c:376 >>  drm_stub_open+0x21a/0x390 drivers/gpu/drm/drm_drv.c:1149 >>  chrdev_open+0x23b/0x6b0 fs/char_dev.c:414 >>  do_dentry_open+0x743/0x1bf0 fs/open.c:956 >>  vfs_open+0x87/0x3f0 fs/open.c:1086 >>  do_open+0x72f/0xf80 fs/namei.c:3830 >>  path_openat+0x2ec/0x770 fs/namei.c:3989 >>  do_filp_open+0x1ff/0x420 fs/namei.c:4016 >>  do_sys_openat2+0x181/0x1e0 fs/open.c:1428 >>  do_sys_open fs/open.c:1443 [inline] >>  __do_sys_openat fs/open.c:1459 [inline] >>  __se_sys_openat fs/open.c:1454 [inline] >>  __x64_sys_openat+0x149/0x210 fs/open.c:1454 >>  do_syscall_x64 arch/x86/entry/common.c:52 [inline] >>  do_syscall_64+0x92/0x180 arch/x86/entry/common.c:83 >>  entry_SYSCALL_64_after_hwframe+0x76/0x7e >> Freed by task 146638: >>  kasan_save_stack+0x30/0x50 mm/kasan/common.c:47 >>  kasan_save_track+0x14/0x30 mm/kasan/common.c:68 >>  kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:576 >>  poison_slab_object mm/kasan/common.c:247 [inline] >>  __kasan_slab_free+0x52/0x70 mm/kasan/common.c:264 >>  kasan_slab_free include/linux/kasan.h:233 [inline] >>  slab_free_hook mm/slub.c:2353 [inline] >>  slab_free mm/slub.c:4609 [inline] >>  kfree+0x14f/0x4d0 mm/slub.c:4757 >>  amdgpu_driver_postclose_kms+0x43d/0x6b0 drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c:1538 [amdgpu] >>  drm_file_free.part.0+0x72d/0xbc0 drivers/gpu/drm/drm_file.c:255 >>  drm_file_free drivers/gpu/drm/drm_file.c:228 [inline] >>  drm_close_helper.isra.0+0x197/0x230 drivers/gpu/drm/drm_file.c:278 >>  drm_release+0x1b0/0x3d0 drivers/gpu/drm/drm_file.c:426 >>  __fput+0x402/0xb50 fs/file_table.c:464 >>  task_work_run+0x155/0x250 kernel/task_work.c:227 >>  resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] >>  exit_to_user_mode_loop kernel/entry/common.c:114 [inline] >>  exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] >>  __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] >>  syscall_exit_to_user_mode+0x26b/0x290 kernel/entry/common.c:218 >>  do_syscall_64+0x9f/0x180 arch/x86/entry/common.c:89 >>  entry_SYSCALL_64_after_hwframe+0x76/0x7e >> The buggy address belongs to the object at ffff888120844000 >> The buggy address is located 1480 bytes inside of >> The buggy address belongs to the physical page: >> page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x120840 >> head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 >> flags: 0x17ffffc0000040(head|node=0|zone=2|lastcpupid=0x1fffff) >> page_type: f5(slab) >> raw: 0017ffffc0000040 ffff88810005c8c0 ffffea0005744c00 dead000000000002 >> raw: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000 >> head: 0017ffffc0000040 ffff88810005c8c0 ffffea0005744c00 dead000000000002 >> head: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000 >> head: 0017ffffc0000003 ffffea0004821001 ffffffffffffffff 0000000000000000 >> head: 0000000000000008 0000000000000000 00000000ffffffff 0000000000000000 >> page dumped because: kasan: bad access detected >> Memory state around the buggy address: >>  ffff888120844480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>  ffff888120844500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>> ffff888120844580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>                                               ^ >>  ffff888120844600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>  ffff888120844680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ================================================================== >> >>  drivers/gpu/drm/scheduler/sched_main.c | 6 ++++-- >>  1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c >> index bfea608a7106..997a2cc1a635 100644 >> --- a/drivers/gpu/drm/scheduler/sched_main.c >> +++ b/drivers/gpu/drm/scheduler/sched_main.c >> @@ -172,8 +172,10 @@ void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity, >> >>   entity->oldest_job_waiting = ts; >> >> - rb_add_cached(&entity->rb_tree_node, &rq->rb_tree_root, >> -       drm_sched_entity_compare_before); >> + if (!entity->stopped) { >> + rb_add_cached(&entity->rb_tree_node, &rq->rb_tree_root, >> +       drm_sched_entity_compare_before); >> + } > > If this is a race, then this patch here is broken, too, because you're > checking the 'stopped' boolean as the callers of that function do, too > – just later. :O > > Could still race, just less likely. > > The proper way to fix it would then be to address the issue where the > locking is supposed to happen. Let's look at, for example, > drm_sched_entity_push_job(): > > > void drm_sched_entity_push_job(struct drm_sched_job *sched_job) > { > (Bla bla bla) > > ………… > > /* first job wakes up scheduler */ > if (first) { > struct drm_gpu_scheduler *sched; > struct drm_sched_rq *rq; > > /* Add the entity to the run queue */ > spin_lock(&entity->lock); > if (entity->stopped) { <---- Aha! > spin_unlock(&entity->lock); > > DRM_ERROR("Trying to push to a killed entity\n"); > return; > } > > rq = entity->rq; > sched = rq->sched; > > spin_lock(&rq->lock); > drm_sched_rq_add_entity(rq, entity); > > if (drm_sched_policy == DRM_SCHED_POLICY_FIFO) > drm_sched_rq_update_fifo_locked(entity, rq, submit_ts); <---- bumm! > > spin_unlock(&rq->lock); > spin_unlock(&entity->lock); > > But the locks are still being hold. So that "shouldn't be happening"(tm). > > Interesting. AFAICS only drm_sched_entity_kill() and drm_sched_fini() > stop entities. The former holds appropriate locks, but drm_sched_fini() > doesn't. So that looks like a hot candidate to me. Opinions? > > On the other hand, aren't drivers prohibited from calling > drm_sched_entity_push_job() after calling drm_sched_fini()? If the > fuzzer does that, then it's not the scheduler's fault. > > Could you test adding spin_lock(&entity->lock) to drm_sched_fini()? > > Would be cool if Tvrtko and Christian take a look. Maybe we even have a > fundamental design issue. It would be nice to have a reproducer and from this thread I did not manage to figure out if the syzkaller snipper James posted was it, or not quite it. In either case, I think one race I see relates to the early exit !entity->rq check before setting entity->stopped in drm_sched_entity_kill(). If the entity was not submitted at all yet (at the time of process exit / entity kill), entity->stopped will therefore not be set. A parallel job submit can then re-add the entity to the tree, as process exit / file close / entity kill is continuing and is about to kfree the entity (in the case of amdgpu report there are two entities embedded in file_priv). One way to make this more robust is to make the entity->rq check in drm_sched_entity_kill() stronger. Or actually to remove it altogether. But I think it also requires checking for entity->stopped in drm_sched_entity_select_rq() and propagating the error code all the way out from drm_sched_job_arm(). That was entity->stopped is properly serialized and acted upon early enough to avoid dereferencing a freed entity and avoid creating jobs not attached to anything (but only have a warning from push job). Disclaimer I haven't tried to experiment with this yet, so I may be missing something. At least writing a reproducer for the race I described sounds easy so unless someone shouts I am talking nonsense I can do that and also sketch out a fix. *If* the theory will hold water after I write the test case. Regards, Tvrtko > >>  } >> >>  /** >