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Cc: Roman Gushchin , Linux Memory Management List , Andrew Morton , Johannes Weiner , Michal Hocko , Shakeel Butt , linux-kernel@vger.kernel.org, syzbot+774c29891415ab0fd29d@syzkaller.appspotmail.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 2A534C0004 X-Stat-Signature: pgxrhw64bibgyn3f6zpg5eabppcjfh6n X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1682319091-743839 X-HE-Meta: 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 wG/RihnU 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun, 23 Apr 2023 at 04:26, Muchun Song wrote: > > On Apr 22, 2023, at 01:40, Roman Gushchin wrote: > > > > KCSAN found an issue in obj_stock_flush_required(): > > stock->cached_objcg can be reset between the check and dereference: > > > > ================================================================== > > 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 > > > > Fix it by reading the cached_objcg with READ_ONCE(). > > > > Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API") > > Reported-by: syzbot+774c29891415ab0fd29d@syzkaller.appspotmail.com > > Reported-by: Dmitry Vyukov > > Link: https://lore.kernel.org/linux-mm/CACT4Y+ZfucZhM60YPphWiCLJr6+SGFhT+jjm8k1P-a_8Kkxsjg@mail.gmail.com/T/#t > > Signed-off-by: Roman Gushchin > > Acked-by: Muchun Song > > Thanks. This improves things, but strictly speaking the write side also needs WRITE_ONCE. Ordering is always a game of two. It's not possible to order things on one side, if the other side messes up the ordering.