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006d021491bc7-68be5775e78mr1181257eaf.10.1775816702924; Fri, 10 Apr 2026 03:25:02 -0700 (PDT) Date: Fri, 10 Apr 2026 03:25:02 -0700 In-Reply-To: X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69d8cffe.a00a0220.468cb.0026.GAE@google.com> Subject: Re: [syzbot] [cgroups?] KASAN: slab-use-after-free Read in pressure_write From: syzbot To: eadavis@qq.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: KASAN: slab-use-after-free Read in pressure_write ================================================================== BUG: KASAN: slab-use-after-free in pressure_write+0xd9/0x290 kernel/cgroup/cgroup.c:4017 Read of size 8 at addr ffff88801f751d08 by task syz.1.588/8362 CPU: 0 UID: 0 PID: 8362 Comm: syz.1.588 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xba/0x230 mm/kasan/report.c:482 kasan_report+0x117/0x150 mm/kasan/report.c:595 pressure_write+0xd9/0x290 kernel/cgroup/cgroup.c:4017 cgroup_file_write+0x36f/0x790 kernel/cgroup/cgroup.c:4317 kernfs_fop_write_iter+0x3b0/0x540 fs/kernfs/file.c:352 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x629/0xba0 fs/read_write.c:688 ksys_write+0x156/0x270 fs/read_write.c:740 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fd26d2ac819 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fd26c906028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fd26d525fa0 RCX: 00007fd26d2ac819 RDX: 000000000000002f RSI: 0000200000000080 RDI: 0000000000000004 RBP: 00007fd26d342c91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fd26d526038 R14: 00007fd26d525fa0 R15: 00007ffda041e108 Allocated by task 8362: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 poison_kmalloc_redzone mm/kasan/common.c:398 [inline] __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415 kasan_kmalloc include/linux/kasan.h:263 [inline] __kmalloc_cache_noprof+0x3a6/0x690 mm/slub.c:5380 kmalloc_noprof include/linux/slab.h:950 [inline] kzalloc_noprof include/linux/slab.h:1188 [inline] cgroup_file_open+0x90/0x3a0 kernel/cgroup/cgroup.c:4262 kernfs_fop_open+0x9eb/0xcb0 fs/kernfs/file.c:724 do_dentry_open+0x83d/0x13e0 fs/open.c:949 vfs_open+0x3b/0x350 fs/open.c:1081 do_open fs/namei.c:4677 [inline] path_openat+0x2e43/0x38a0 fs/namei.c:4836 do_file_open+0x23e/0x4a0 fs/namei.c:4865 do_sys_openat2+0x113/0x200 fs/open.c:1366 do_sys_open fs/open.c:1372 [inline] __do_sys_openat fs/open.c:1388 [inline] __se_sys_openat fs/open.c:1383 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1383 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 8359: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2685 [inline] slab_free mm/slub.c:6165 [inline] kfree+0x1c1/0x6c0 mm/slub.c:6483 cgroup_file_release+0xd6/0x100 kernel/cgroup/cgroup.c:4289 kernfs_release_file fs/kernfs/file.c:764 [inline] kernfs_drain_open_files+0x392/0x720 fs/kernfs/file.c:834 kernfs_drain+0x470/0x600 fs/kernfs/dir.c:525 __kernfs_remove+0x3cf/0x660 fs/kernfs/dir.c:1513 kernfs_remove_by_name_ns+0xaf/0x130 fs/kernfs/dir.c:1722 kernfs_remove_by_name include/linux/kernfs.h:633 [inline] cgroup_rm_file kernel/cgroup/cgroup.c:1758 [inline] cgroup_addrm_files+0x684/0xc30 kernel/cgroup/cgroup.c:4489 cgroup_destroy_locked+0x321/0x630 kernel/cgroup/cgroup.c:6203 cgroup_rmdir+0x3e8/0x710 kernel/cgroup/cgroup.c:6317 kernfs_iop_rmdir+0x203/0x350 fs/kernfs/dir.c:1291 vfs_rmdir+0x400/0x6f0 fs/namei.c:5344 filename_rmdir+0x292/0x520 fs/namei.c:5399 __do_sys_rmdir fs/namei.c:5422 [inline] __se_sys_rmdir+0x2e/0x140 fs/namei.c:5419 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff88801f751d00 which belongs to the cache kmalloc-192 of size 192 The buggy address is located 8 bytes inside of freed 192-byte region [ffff88801f751d00, ffff88801f751dc0) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1f751 flags: 0x80000000000000(node=0|zone=1) page_type: f5(slab) raw: 0080000000000000 ffff88813fe1a3c0 dead000000000100 dead000000000122 raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 0, migratetype Unmovable, gfp_mask 0xd2cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 4617252166, free_ts 4598829481 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889 prep_new_page mm/page_alloc.c:1897 [inline] get_page_from_freelist+0x28bb/0x2950 mm/page_alloc.c:3962 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250 alloc_slab_page mm/slub.c:3292 [inline] allocate_slab+0x77/0x660 mm/slub.c:3481 new_slab mm/slub.c:3539 [inline] refill_objects+0x334/0x3c0 mm/slub.c:7175 refill_sheaf mm/slub.c:2812 [inline] __pcs_replace_empty_main+0x35c/0x710 mm/slub.c:4615 alloc_from_pcs mm/slub.c:4717 [inline] slab_alloc_node mm/slub.c:4851 [inline] __kmalloc_cache_noprof+0x44e/0x690 mm/slub.c:5375 kmalloc_noprof include/linux/slab.h:950 [inline] kzalloc_noprof include/linux/slab.h:1188 [inline] call_usermodehelper_setup+0x8e/0x270 kernel/umh.c:362 kobject_uevent_env+0x65b/0x9e0 lib/kobject_uevent.c:628 driver_register+0x2d4/0x320 drivers/base/driver.c:257 ioat_init_module+0x144/0x1d0 drivers/dma/ioat/init.c:1433 do_one_initcall+0x250/0x8d0 init/main.c:1382 do_initcall_level+0x104/0x190 init/main.c:1444 do_initcalls+0x59/0xa0 init/main.c:1460 kernel_init_freeable+0x2a6/0x3e0 init/main.c:1692 kernel_init+0x1d/0x1d0 init/main.c:1582 page last free pid 43 tgid 43 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] __free_pages_prepare mm/page_alloc.c:1433 [inline] __free_frozen_pages+0xfe3/0x1170 mm/page_alloc.c:2978 vfree+0x2ac/0x470 mm/vmalloc.c:3479 delayed_vfree_work+0x55/0x80 mm/vmalloc.c:3398 process_one_work kernel/workqueue.c:3276 [inline] process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 Memory state around the buggy address: ffff88801f751c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff88801f751c80: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc >ffff88801f751d00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88801f751d80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ffff88801f751e00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== Tested on: commit: 9a9c8ce3 Merge tag 'kbuild-fixes-7.0-4' of git://git.k.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1335574e580000 kernel config: https://syzkaller.appspot.com/x/.config?x=45cb3c58fd963c27 dashboard link: https://syzkaller.appspot.com/bug?extid=33e571025d88efd1312c compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 patch: https://syzkaller.appspot.com/x/patch.diff?x=17b97bd6580000