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Message-ID: <e7c0f63678a93261182b69aa526217821552a150.camel@mailbox.org>
Date: Mon, 21 Jul 2025 10:16:05 +0200
From: Philipp Stanner <phasta@...lbox.org>
To: phasta@...nel.org, James Flowers <bold.zone2373@...tmail.com>,
matthew.brost@...el.com, dakr@...nel.org, ckoenig.leichtzumerken@...il.com,
maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch,
skhan@...uxfoundation.org
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
linux-kernel-mentees@...ts.linux.dev, Tvrtko Ursulin
<tvrtko.ursulin@...lia.com>
Subject: Re: [PATCH] drm/sched: Prevent stopped entities from being added to
the run queue.
On Mon, 2025-07-21 at 09:52 +0200, 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 <bold.zone2373@...tmail.com>
> > ---
> > 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:
> > <TASK>
> > __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
> > </TASK>
> > 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:
> > <TASK>
> > __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
> > </TASK>
> > 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:
> > <TASK>
> > __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
> > </TASK>
> > 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:
> > <TASK>
> > __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
> > </TASK>
> > 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()?
Ah no, forget about that.
In drm_sched_fini(), you'd have to take the locks in reverse order as
in drm_sched_entity_push/pop_job(), thereby replacing race with
deadlock.
I suspect that this is an issue in amdgpu. But let's wait for
Christian.
P.
>
> Would be cool if Tvrtko and Christian take a look. Maybe we even have a
> fundamental design issue.
>
>
> Regards
> P.
>
>
> > }
> >
> > /**
>
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