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AJvYcCUj7V+E2TvMdloCBnAYbEPDsbDMObNeFkiiCKAzvHO2woZWnGwnOd2AYoXoEGjlGSzKr77aJUmcbivcnvg=@vger.kernel.org X-Gm-Message-State: AOJu0YwxJD/KU7c78gBWZO32sf3V/mJ/2uKdVVxVlAZwy94MuDNMw22K 7xulhaTsA7o5UJrGEa8gz7ik4tTKfrD5tnxLhNgKnzecT8Qm6/IxO95SaVkp4PliRDkCzWAjChm ygPcYyVxscHrdKaphnEw9Rc73kafTvOJ3zbOjnukJRRD+kKXAOJ/1xI1EE3M= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a4a:dd92:0:b0:67b:dad6:dbdc with SMTP id 006d021491bc7-67bdad6dc6dmr5013569eaf.55.1773599848438; Sun, 15 Mar 2026 11:37:28 -0700 (PDT) Date: Sun, 15 Mar 2026 11:37:28 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69b6fc68.a00a0220.3b25d1.001e.GAE@google.com> Subject: [syzbot] [mm?] possible deadlock in mfill_get_vma From: syzbot To: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, peterx@redhat.com, rppt@kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: b84a0ebe421c Add linux-next specific files for 20260313 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=131ab8da580000 kernel config: https://syzkaller.appspot.com/x/.config?x=e7280ad1f68b2dce dashboard link: https://syzkaller.appspot.com/bug?extid=c473aa669b5e8a6f48d2 compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=126c98ba580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1644a2d6580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/09145161a8a9/disk-b84a0ebe.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/b64c254e474c/vmlinux-b84a0ebe.xz kernel image: https://storage.googleapis.com/syzbot-assets/a7c33f5f7f45/bzImage-b84a0ebe.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+c473aa669b5e8a6f48d2@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.0.17/5990 is trying to acquire lock: ffff88802caef3b8 (&mm->mmap_lock){++++}-{4:4}, at: __might_fault+0xaf/0x130 mm/memory.c:7249 but task is already holding lock: ffff88807cdbccf0 (&ctx->map_changing_lock){.+.+}-{4:4}, at: mfill_get_vma+0x162/0x660 mm/userfaultfd.c:226 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&ctx->map_changing_lock){.+.+}-{4:4}: down_read+0x47/0x2e0 kernel/locking/rwsem.c:1568 mfill_get_vma+0x162/0x660 mm/userfaultfd.c:226 mfill_atomic mm/userfaultfd.c:900 [inline] mfill_atomic_continue+0x189/0x12c0 mm/userfaultfd.c:974 userfaultfd_continue fs/userfaultfd.c:1806 [inline] userfaultfd_ioctl+0x232d/0x4c70 fs/userfaultfd.c:2071 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 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 -> #1 (vm_lock){++++}-{0:0}: __vma_start_exclude_readers+0x28a/0x940 mm/mmap_lock.c:125 __vma_start_write+0xdc/0x290 mm/mmap_lock.c:148 vma_start_write include/linux/mmap_lock.h:303 [inline] mprotect_fixup+0x5eb/0xa80 mm/mprotect.c:768 setup_arg_pages+0x565/0xac0 fs/exec.c:670 load_elf_binary+0xc5e/0x2980 fs/binfmt_elf.c:1029 search_binary_handler fs/exec.c:1664 [inline] exec_binprm fs/exec.c:1696 [inline] bprm_execve+0x949/0x1470 fs/exec.c:1748 kernel_execve+0x844/0x930 fs/exec.c:1892 try_to_run_init_process+0x13/0x60 init/main.c:1514 kernel_init+0xad/0x1d0 init/main.c:1642 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 (&mm->mmap_lock){++++}-{4:4}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868 __might_fault+0xcb/0x130 mm/memory.c:7249 userfaultfd_continue fs/userfaultfd.c:1813 [inline] userfaultfd_ioctl+0x2372/0x4c70 fs/userfaultfd.c:2071 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 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 other info that might help us debug this: Chain exists of: &mm->mmap_lock --> vm_lock --> &ctx->map_changing_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(&ctx->map_changing_lock); lock(vm_lock); lock(&ctx->map_changing_lock); rlock(&mm->mmap_lock); *** DEADLOCK *** 2 locks held by syz.0.17/5990: #0: ffff88807c119d08 (vm_lock){++++}-{0:0}, at: lock_vma_under_rcu+0x1d1/0x500 mm/mmap_lock.c:310 #1: ffff88807cdbccf0 (&ctx->map_changing_lock){.+.+}-{4:4}, at: mfill_get_vma+0x162/0x660 mm/userfaultfd.c:226 stack backtrace: CPU: 0 UID: 0 PID: 5990 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868 __might_fault+0xcb/0x130 mm/memory.c:7249 userfaultfd_continue fs/userfaultfd.c:1813 [inline] userfaultfd_ioctl+0x2372/0x4c70 fs/userfaultfd.c:2071 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 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: 0033:0x7f478759c799 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:00007ffcc2bbac28 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f4787815fa0 RCX: 00007f478759c799 RDX: 0000200000000080 RSI: 00000000c020aa07 RDI: 0000000000000003 RBP: 00007f4787632c99 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f4787815fac R14: 00007f4787815fa0 R15: 00007f4787815fa0 --- 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@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title 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. If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup