Hello, When using Syzkaller to fuzz the latest Linux kernel, the following crash was triggered. HEAD commit: a7904a538933 Linux 5.16-rc6 git tree: upstream console output: KCSAN: data-race in task_mem / unmap_region kernel config: https://paste.ubuntu.com/p/QB39MJKWKb/plain/ Syzlang reproducer: https://paste.ubuntu.com/p/q2DVwVh6hr/plain/ If you fix this issue, please add the following tag to the commit: Reported-by: Hypericum <hypericumperforatum4444@xxxxxxxxx> I think fs/proc/task_mmu.c visits the variable mm without locking and another mmap visits mm->hiwater_vm resulting in a data race. reproducer log: https://paste.ubuntu.com/p/Sp6RDWKDfy/plain/ reproducer report: ================================================================== BUG: KCSAN: data-race in task_mem / unmap_region write to 0xffff8881095008b0 of 8 bytes by task 3712 on cpu 4: update_hiwater_rss include/linux/mm.h:2102 [inline] unmap_region+0x12b/0x1e0 mm/mmap.c:2648 __do_munmap+0xe6e/0x12b0 mm/mmap.c:2883 __vm_munmap mm/mmap.c:2906 [inline] __do_sys_munmap+0x9f/0x160 mm/mmap.c:2932 __se_sys_munmap mm/mmap.c:2928 [inline] __x64_sys_munmap+0x2d/0x40 mm/mmap.c:2928 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae read to 0xffff8881095008b0 of 8 bytes by task 1512 on cpu 7: task_mem+0xfb/0x3d0 fs/proc/task_mmu.c:50 proc_pid_status+0x890/0x14d0 fs/proc/array.c:438 proc_single_show+0x84/0x100 fs/proc/base.c:778 seq_read_iter+0x2e3/0x930 fs/seq_file.c:230 seq_read+0x234/0x280 fs/seq_file.c:162 vfs_read+0x1e6/0x730 fs/read_write.c:479 ksys_read+0xd9/0x190 fs/read_write.c:619 __do_sys_read fs/read_write.c:629 [inline] __se_sys_read fs/read_write.c:627 [inline] __x64_sys_read+0x3e/0x50 fs/read_write.c:627 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae value changed: 0x000000000000065b -> 0x0000000000000662 Reported by Kernel Concurrency Sanitizer on: CPU: 7 PID: 1512 Comm: systemd-journal Not tainted 5.16.0-rc8+ #11 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 ==================================================================
