syzbot has found a reproducer for the following issue on: HEAD commit: c664e16bb1ba Merge tag 'docs-6.8-fixes2' of git://git.lwn... git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=14f8d1e0180000 kernel config: https://syzkaller.appspot.com/x/.config?x=df82262440d95bc4 dashboard link: https://syzkaller.appspot.com/bug?extid=0f999d26a4fd79c3a23b compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1086cd48180000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11fcdba2180000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-c664e16b.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/c838390fdb6c/vmlinux-c664e16b.xz kernel image: https://storage.googleapis.com/syzbot-assets/d25123cb1896/bzImage-c664e16b.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+0f999d26a4fd79c3a23b@xxxxxxxxxxxxxxxxxxxxxxxxx ================================================================== BUG: KASAN: slab-use-after-free in drm_atomic_helper_wait_for_vblanks.part.0+0x84f/0x930 drivers/gpu/drm/drm_atomic_helper.c:1661 Read of size 1 at addr ffff88802d6f0409 by task kworker/u16:1/13 CPU: 1 PID: 13 Comm: kworker/u16:1 Not tainted 6.8.0-rc4-syzkaller-00005-gc664e16bb1ba #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 Workqueue: events_unbound commit_work Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:377 [inline] print_report+0xc4/0x620 mm/kasan/report.c:488 kasan_report+0xda/0x110 mm/kasan/report.c:601 drm_atomic_helper_wait_for_vblanks.part.0+0x84f/0x930 drivers/gpu/drm/drm_atomic_helper.c:1661 drm_atomic_helper_wait_for_vblanks drivers/gpu/drm/drm_atomic_helper.c:1657 [inline] drm_atomic_helper_commit_tail+0xcb/0xf0 drivers/gpu/drm/drm_atomic_helper.c:1757 commit_tail+0x356/0x410 drivers/gpu/drm/drm_atomic_helper.c:1834 process_one_work+0x889/0x15e0 kernel/workqueue.c:2633 process_scheduled_works kernel/workqueue.c:2706 [inline] worker_thread+0x8b9/0x12a0 kernel/workqueue.c:2787 kthread+0x2c6/0x3b0 kernel/kthread.c:388 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:242 </TASK> Allocated by task 5401: kasan_save_stack+0x33/0x60 mm/kasan/common.c:47 kasan_save_track+0x14/0x30 mm/kasan/common.c:68 poison_kmalloc_redzone mm/kasan/common.c:372 [inline] __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:389 kmalloc include/linux/slab.h:590 [inline] drm_atomic_helper_crtc_duplicate_state+0x70/0xd0 drivers/gpu/drm/drm_atomic_state_helper.c:177 drm_atomic_get_crtc_state+0x162/0x440 drivers/gpu/drm/drm_atomic.c:362 page_flip_common+0x57/0x320 drivers/gpu/drm/drm_atomic_helper.c:3629 drm_atomic_helper_page_flip+0xb6/0x190 drivers/gpu/drm/drm_atomic_helper.c:3690 drm_mode_page_flip_ioctl+0x103f/0x1470 drivers/gpu/drm/drm_plane.c:1489 drm_ioctl_kernel+0x1ec/0x3e0 drivers/gpu/drm/drm_ioctl.c:744 drm_ioctl+0x5d8/0xc00 drivers/gpu/drm/drm_ioctl.c:841 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x193/0x220 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xd5/0x270 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x6f/0x77 Freed by task 5401: kasan_save_stack+0x33/0x60 mm/kasan/common.c:47 kasan_save_track+0x14/0x30 mm/kasan/common.c:68 kasan_save_free_info+0x3f/0x60 mm/kasan/generic.c:640 poison_slab_object mm/kasan/common.c:241 [inline] __kasan_slab_free+0x121/0x1c0 mm/kasan/common.c:257 kasan_slab_free include/linux/kasan.h:184 [inline] slab_free_hook mm/slub.c:2121 [inline] slab_free mm/slub.c:4299 [inline] kfree+0x124/0x370 mm/slub.c:4409 drm_atomic_state_default_clear+0x3aa/0xde0 drivers/gpu/drm/drm_atomic.c:225 drm_atomic_state_clear drivers/gpu/drm/drm_atomic.c:294 [inline] __drm_atomic_state_free+0x185/0x2b0 drivers/gpu/drm/drm_atomic.c:311 kref_put include/linux/kref.h:65 [inline] drm_atomic_state_put include/drm/drm_atomic.h:490 [inline] drm_client_modeset_commit_atomic+0x6db/0x810 drivers/gpu/drm/drm_client_modeset.c:1057 drm_client_modeset_commit_locked+0x14d/0x580 drivers/gpu/drm/drm_client_modeset.c:1154 drm_client_modeset_commit+0x4f/0x80 drivers/gpu/drm/drm_client_modeset.c:1180 __drm_fb_helper_restore_fbdev_mode_unlocked drivers/gpu/drm/drm_fb_helper.c:251 [inline] __drm_fb_helper_restore_fbdev_mode_unlocked drivers/gpu/drm/drm_fb_helper.c:230 [inline] drm_fb_helper_restore_fbdev_mode_unlocked drivers/gpu/drm/drm_fb_helper.c:278 [inline] drm_fb_helper_lastclose+0xc7/0x160 drivers/gpu/drm/drm_fb_helper.c:2005 drm_fbdev_generic_client_restore+0x2c/0x40 drivers/gpu/drm/drm_fbdev_generic.c:258 drm_client_dev_restore+0x188/0x2a0 drivers/gpu/drm/drm_client.c:247 drm_release+0x32f/0x3e0 drivers/gpu/drm/drm_file.c:437 __fput+0x270/0xb80 fs/file_table.c:376 __fput_sync+0x47/0x50 fs/file_table.c:461 __do_sys_close fs/open.c:1554 [inline] __se_sys_close fs/open.c:1539 [inline] __x64_sys_close+0x87/0x100 fs/open.c:1539 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xd5/0x270 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x6f/0x77 The buggy address belongs to the object at ffff88802d6f0400 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 9 bytes inside of freed 512-byte region [ffff88802d6f0400, ffff88802d6f0600) The buggy address belongs to the physical page: page:ffffea0000b5bc00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2d6f0 head:ffffea0000b5bc00 order:2 entire_mapcount:0 nr_pages_mapped:0 pincount:0 flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff) page_type: 0xffffffff() raw: 00fff00000000840 ffff888014c42c80 dead000000000122 0000000000000000 raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5401, tgid 5401 (syz-executor102), ts 53592743984, free_ts 53573722996 set_page_owner include/linux/page_owner.h:31 [inline] post_alloc_hook+0x2d4/0x350 mm/page_alloc.c:1533 prep_new_page mm/page_alloc.c:1540 [inline] get_page_from_freelist+0xa28/0x3780 mm/page_alloc.c:3311 __alloc_pages+0x22f/0x2440 mm/page_alloc.c:4567 __alloc_pages_node include/linux/gfp.h:238 [inline] alloc_pages_node include/linux/gfp.h:261 [inline] alloc_slab_page mm/slub.c:2190 [inline] allocate_slab mm/slub.c:2354 [inline] new_slab+0xcc/0x3a0 mm/slub.c:2407 ___slab_alloc+0x4af/0x19a0 mm/slub.c:3540 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3625 __slab_alloc_node mm/slub.c:3678 [inline] slab_alloc_node mm/slub.c:3850 [inline] kmalloc_trace+0x30b/0x340 mm/slub.c:4007 kmalloc include/linux/slab.h:590 [inline] kzalloc include/linux/slab.h:711 [inline] drm_master_create+0x43/0x4d0 drivers/gpu/drm/drm_auth.c:136 drm_new_set_master+0xd6/0x450 drivers/gpu/drm/drm_auth.c:172 drm_master_open+0x181/0x1f0 drivers/gpu/drm/drm_auth.c:342 drm_open_helper+0x3fc/0x500 drivers/gpu/drm/drm_file.c:330 drm_open+0x1a0/0x490 drivers/gpu/drm/drm_file.c:380 drm_stub_open+0x28e/0x430 drivers/gpu/drm/drm_drv.c:1046 chrdev_open+0x26d/0x6f0 fs/char_dev.c:414 do_dentry_open+0x8da/0x18c0 fs/open.c:953 do_open fs/namei.c:3641 [inline] path_openat+0x1e00/0x29a0 fs/namei.c:3798 page last free pid 5398 tgid 5398 stack trace: reset_page_owner include/linux/page_owner.h:24 [inline] free_pages_prepare mm/page_alloc.c:1140 [inline] free_unref_page_prepare+0x527/0xb10 mm/page_alloc.c:2346 free_unref_page+0x33/0x3c0 mm/page_alloc.c:2486 rcu_do_batch kernel/rcu/tree.c:2190 [inline] rcu_core+0x819/0x1680 kernel/rcu/tree.c:2465 __do_softirq+0x21c/0x8e7 kernel/softirq.c:553 Memory state around the buggy address: ffff88802d6f0300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88802d6f0380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88802d6f0400: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88802d6f0480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88802d6f0500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== --- If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing.
