On Fri, 21 Apr 2023 at 16:33, syzbot <syzbot+774c29891415ab0fd29d@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: 534293368afa Merge tag 'kbuild-fixes-v6.3' of git://git.ke.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=11a0c26ec80000 > kernel config: https://syzkaller.appspot.com/x/.config?x=85fa20c996a2e46d > dashboard link: https://syzkaller.appspot.com/bug?extid=774c29891415ab0fd29d > compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/ec0e584af797/disk-53429336.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/423a67f52f94/vmlinux-53429336.xz > kernel image: https://storage.googleapis.com/syzbot-assets/8409b9716faa/bzImage-53429336.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+774c29891415ab0fd29d@xxxxxxxxxxxxxxxxxxxxxxxxx Here this: stock->cached_objcg = NULL; runs concurrently with: if (stock->cached_objcg) { memcg = obj_cgroup_memcg(stock->cached_objcg); If I am reading this correctly, this can cause a NULL deref, if cached_objcg is reset between the check and the use. > ================================================================== > BUG: KCSAN: data-race in drain_all_stock / drain_obj_stock > > write to 0xffff888237c2a2f8 of 8 bytes by task 19625 on cpu 0: > drain_obj_stock+0x408/0x4e0 mm/memcontrol.c:3306 > refill_obj_stock+0x9c/0x1e0 mm/memcontrol.c:3340 > obj_cgroup_uncharge+0xe/0x10 mm/memcontrol.c:3408 > memcg_slab_free_hook mm/slab.h:587 [inline] > __cache_free mm/slab.c:3373 [inline] > __do_kmem_cache_free mm/slab.c:3577 [inline] > kmem_cache_free+0x105/0x280 mm/slab.c:3602 > __d_free fs/dcache.c:298 [inline] > dentry_free fs/dcache.c:375 [inline] > __dentry_kill+0x422/0x4a0 fs/dcache.c:621 > dentry_kill+0x8d/0x1e0 > dput+0x118/0x1f0 fs/dcache.c:913 > __fput+0x3bf/0x570 fs/file_table.c:329 > ____fput+0x15/0x20 fs/file_table.c:349 > task_work_run+0x123/0x160 kernel/task_work.c:179 > resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] > exit_to_user_mode_loop+0xcf/0xe0 kernel/entry/common.c:171 > exit_to_user_mode_prepare+0x6a/0xa0 kernel/entry/common.c:203 > __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline] > syscall_exit_to_user_mode+0x26/0x140 kernel/entry/common.c:296 > do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > read to 0xffff888237c2a2f8 of 8 bytes by task 19632 on cpu 1: > obj_stock_flush_required mm/memcontrol.c:3319 [inline] > drain_all_stock+0x174/0x2a0 mm/memcontrol.c:2361 > try_charge_memcg+0x6d0/0xd10 mm/memcontrol.c:2703 > try_charge mm/memcontrol.c:2837 [inline] > mem_cgroup_charge_skmem+0x51/0x140 mm/memcontrol.c:7290 > sock_reserve_memory+0xb1/0x390 net/core/sock.c:1025 > sk_setsockopt+0x800/0x1e70 net/core/sock.c:1525 > udp_lib_setsockopt+0x99/0x6c0 net/ipv4/udp.c:2692 > udp_setsockopt+0x73/0xa0 net/ipv4/udp.c:2817 > sock_common_setsockopt+0x61/0x70 net/core/sock.c:3668 > __sys_setsockopt+0x1c3/0x230 net/socket.c:2271 > __do_sys_setsockopt net/socket.c:2282 [inline] > __se_sys_setsockopt net/socket.c:2279 [inline] > __x64_sys_setsockopt+0x66/0x80 net/socket.c:2279 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > value changed: 0xffff8881382d52c0 -> 0xffff888138893740 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 1 PID: 19632 Comm: syz-executor.0 Not tainted 6.3.0-rc2-syzkaller-00387-g534293368afa #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023 > ================================================================== > > > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/00000000000058b63f05f9d98811%40google.com.
