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Message-ID: <20260124113148.2398-1-hdanton@sina.com>
Date: Sat, 24 Jan 2026 19:31:47 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+4e70c8e0a2017b432f7a@...kaller.appspotmail.com>
Cc: axboe@...nel.dk,
linux-block@...r.kernel.org,
Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
Suren Baghdasaryan <surenb@...gle.com>,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [block?] possible deadlock in blkdev_read_iter
Add Lorenzo and Suren
> Date: Fri, 23 Jan 2026 15:14:36 -0800
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 24d479d26b25 Linux 6.19-rc6
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=100033fa580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=1859476832863c41
> dashboard link: https://syzkaller.appspot.com/bug?extid=4e70c8e0a2017b432f7a
> compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11451b9a580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1045e852580000
>
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-24d479d2.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/d0f3c47f6869/vmlinux-24d479d2.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/800231513703/bzImage-24d479d2.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+4e70c8e0a2017b432f7a@...kaller.appspotmail.com
>
> WARNING: possible circular locking dependency detected
> syzkaller #0 Not tainted
> ------------------------------------------------------
> syz.0.17/6091 is trying to acquire lock:
> ffff8881061287a8 (
> &sb->s_type->i_mutex_key#8){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1042 [inline]
> &sb->s_type->i_mutex_key#8){++++}-{4:4}, at: blkdev_read_iter+0x19e/0x500 block/fops.c:855
>
> but task is already holding lock:
> ffff888012aa0448 (vm_lock){++++}-{0:0}, at: lock_next_vma+0x10e/0xed0 mm/mmap_lock.c:334
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #2 (vm_lock){++++}-{0:0}:
> __vma_enter_locked+0x260/0x770 mm/mmap_lock.c:72
> __vma_start_write+0x21/0x160 mm/mmap_lock.c:104
> vma_start_write include/linux/mmap_lock.h:213 [inline]
> mprotect_fixup+0x4e3/0xb80 mm/mprotect.c:768
> setup_arg_pages+0x4a2/0xbb0 fs/exec.c:670
> load_elf_binary+0xb5b/0x4fe0 fs/binfmt_elf.c:1028
> search_binary_handler fs/exec.c:1669 [inline]
> exec_binprm fs/exec.c:1701 [inline]
> bprm_execve fs/exec.c:1753 [inline]
> bprm_execve+0x8c2/0x1620 fs/exec.c:1729
> kernel_execve+0x2ef/0x3b0 fs/exec.c:1919
> try_to_run_init_process init/main.c:1506 [inline]
> kernel_init+0x14a/0x2b0 init/main.c:1634
> ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
>
> -> #1 (&mm->mmap_lock){++++}-{4:4}:
> __might_fault mm/memory.c:7174 [inline]
> __might_fault+0x113/0x190 mm/memory.c:7168
> _copy_to_iter+0x1c2/0x1710 lib/iov_iter.c:196
> copy_page_to_iter lib/iov_iter.c:374 [inline]
> copy_page_to_iter+0x12a/0x1e0 lib/iov_iter.c:361
> copy_folio_to_iter include/linux/uio.h:204 [inline]
> filemap_read+0x6b1/0xe40 mm/filemap.c:2851
> blkdev_read_iter+0x1ac/0x500 block/fops.c:856
> new_sync_read fs/read_write.c:491 [inline]
> vfs_read+0x8bf/0xcf0 fs/read_write.c:572
> ksys_read+0x12a/0x250 fs/read_write.c:715
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> -> #0 (&sb->s_type->i_mutex_key#8){++++}-{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+0x1669/0x2890 kernel/locking/lockdep.c:5237
> lock_acquire kernel/locking/lockdep.c:5868 [inline]
> lock_acquire+0x179/0x330 kernel/locking/lockdep.c:5825
> down_read+0x9b/0x460 kernel/locking/rwsem.c:1537
> inode_lock_shared include/linux/fs.h:1042 [inline]
> blkdev_read_iter+0x19e/0x500 block/fops.c:855
> __kernel_read+0x3f3/0xbf0 fs/read_write.c:530
> freader_fetch+0x1d7/0x9d0 lib/buildid.c:100
> __build_id_parse.isra.0+0xdd/0x6c0 lib/buildid.c:297
> do_procmap_query+0xb0e/0x1080 fs/proc/task_mmu.c:733
> procfs_procmap_ioctl+0x9d/0xe0 fs/proc/task_mmu.c:813
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:597 [inline]
> __se_sys_ioctl fs/ioctl.c:583 [inline]
> __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xcd/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:
> &sb->s_type->i_mutex_key#8 --> &mm->mmap_lock --> vm_lock
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> rlock(vm_lock);
> lock(&mm->mmap_lock);
> lock(vm_lock);
> rlock(&sb->s_type->i_mutex_key#8);
>
> *** DEADLOCK ***
>
> 1 lock held by syz.0.17/6091:
> #0: ffff888012aa0448 (vm_lock){++++}-{0:0}, at: lock_next_vma+0x10e/0xed0 mm/mmap_lock.c:334
>
> stack backtrace:
> CPU: 2 UID: 0 PID: 6091 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
> Call Trace:
> <TASK>
> __dump_stack lib/dump_stack.c:94 [inline]
> dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
> print_circular_bug+0x275/0x340 kernel/locking/lockdep.c:2043
> check_noncircular+0x146/0x160 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+0x1669/0x2890 kernel/locking/lockdep.c:5237
> lock_acquire kernel/locking/lockdep.c:5868 [inline]
> lock_acquire+0x179/0x330 kernel/locking/lockdep.c:5825
> down_read+0x9b/0x460 kernel/locking/rwsem.c:1537
> inode_lock_shared include/linux/fs.h:1042 [inline]
> blkdev_read_iter+0x19e/0x500 block/fops.c:855
> __kernel_read+0x3f3/0xbf0 fs/read_write.c:530
> freader_fetch+0x1d7/0x9d0 lib/buildid.c:100
> __build_id_parse.isra.0+0xdd/0x6c0 lib/buildid.c:297
> do_procmap_query+0xb0e/0x1080 fs/proc/task_mmu.c:733
> procfs_procmap_ioctl+0x9d/0xe0 fs/proc/task_mmu.c:813
> vfs_ioctl fs/ioctl.c:51 [inline]
> __do_sys_ioctl fs/ioctl.c:597 [inline]
> __se_sys_ioctl fs/ioctl.c:583 [inline]
> __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7ff1a238f7c9
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffebbe538b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007ff1a25e5fa0 RCX: 00007ff1a238f7c9
> RDX: 0000200000000180 RSI: 00000000c0686611 RDI: 0000000000000004
> RBP: 00007ff1a2413f91 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ff1a25e5fa0 R14: 00007ff1a25e5fa0 R15: 0000000000000003
> </TASK>
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