possible deadlock in gup_fast

ID	Workflow	Result	Correct	Bug	Created	Started	Finished	Revision	Error
04b67007-6f59-42a8-b998-51dffeca2149	assessment-security	DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌	❓	possible deadlock in gup_fast_fallback (3)	2026/06/01 09:18	2026/06/01 09:18	2026/06/01 10:16	6b4a844333e83556da95d61d7f207e7ef5cd4bc6
f6c190a3-a96c-4bb4-a5fc-e95f95fe5e51	assessment-security		💥	possible deadlock in gup_fast_fallback (3)	2026/05/15 10:50	2026/05/15 10:50	2026/05/15 10:51	9cd3beaadf14b3a22d15fd97a0bf081ee41ebe01	failed to run ["git" "-c" "core.hooksPath=/dev/null" "checkout" "1f8fd0fe56412db6a1a84317ce5856bdbef1fca3"]: exit status 128 error: unable to write file tools/testing/selftests/mm/guard-regions.c erro... truncated to first 200 bytes; open job for full error

Title	Replies (including bot)	Last reply
[syzbot] [mm?] possible deadlock in gup_fast_fallback (3)	1 (2)	2026/05/13 11:44

Title

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[syzbot] [mm?] possible deadlock in gup_fast_fallback (3)

1 (2)

2026/05/13 11:44

Kernel	Title	Rank 🛈	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	possible deadlock in gup_fast_fallback mm	4	C	done	inconclusive	2729	310d	787d	0/29	auto-obsoleted due to no activity on 2025/10/20 12:51
upstream	possible deadlock in gup_fast_fallback (2) mm	4	C			21	43d	131d	29/29	fixed on 2026/05/06 16:40

Rank 🛈

upstream

possible deadlock in gup_fast_fallback mm

done

inconclusive

2729

310d

787d

0/29

auto-obsoleted due to no activity on 2025/10/20 12:51

upstream

possible deadlock in gup_fast_fallback (2) mm

43d

131d

29/29

fixed on 2026/05/06 16:40

====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.1.2126/13673 is trying to acquire lock: ffff888034ffb438 (&mm->mmap_lock){++++}-{4:4}, at: gup_fast_fallback+0x20d/0x20d0 mm/gup.c:3193 but task is already holding lock: ffff8880359d8fe0 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline] ffff8880359d8fe0 (sk_lock-AF_INET6){+.+.}-{0:0}, at: tls_sw_sendmsg+0x15e/0x2400 net/tls/tls_sw.c:1301 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #7 (sk_lock-AF_INET6){+.+.}-{0:0}: lock_sock_nested+0x41/0x100 net/core/sock.c:3792 lock_sock include/net/sock.h:1713 [inline] inet_shutdown+0x6a/0x390 net/ipv4/af_inet.c:915 nbd_mark_nsock_dead+0x2cb/0x550 drivers/block/nbd.c:318 recv_work+0x1cef/0x1e10 drivers/block/nbd.c:1021 process_one_work kernel/workqueue.c:3314 [inline] process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3397 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3478 kthread+0x389/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #6 (&nsock->tx_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1590 kernel/locking/mutex.c:820 nbd_handle_cmd drivers/block/nbd.c:1143 [inline] nbd_queue_rq+0x373/0x1150 drivers/block/nbd.c:1207 blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2148 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline] blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline] __blk_mq_sched_dispatch_requests+0xd36/0x1580 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329 blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2387 blk_mq_dispatch_list+0xd11/0xe10 include/linux/spinlock.h:-1 blk_mq_flush_plug_list+0x45f/0x540 block/blk-mq.c:2997 __blk_flush_plug+0x3ed/0x4d0 block/blk-core.c:1230 blk_finish_plug block/blk-core.c:1257 [inline] __submit_bio+0x465/0x560 block/blk-core.c:649 __submit_bio_noacct_mq block/blk-core.c:722 [inline] submit_bio_noacct_nocheck+0x2f4/0xa40 block/blk-core.c:753 submit_bh fs/buffer.c:2742 [inline] block_read_full_folio+0x599/0x830 fs/buffer.c:2344 filemap_read_folio+0x12c/0x3a0 mm/filemap.c:2502 do_read_cache_folio+0x354/0x590 mm/filemap.c:4107 read_mapping_folio include/linux/pagemap.h:1017 [inline] read_part_sector+0xb6/0x2b0 block/partitions/core.c:724 adfspart_check_ICS+0xb1/0x960 block/partitions/acorn.c:356 check_partition block/partitions/core.c:143 [inline] blk_add_partitions block/partitions/core.c:591 [inline] bdev_disk_changed+0x82b/0x1780 block/partitions/core.c:695 blkdev_get_whole+0x372/0x510 block/bdev.c:756 bdev_open+0x324/0xd70 block/bdev.c:965 blkdev_open+0x461/0x600 block/fops.c:697 do_dentry_open+0x816/0x1380 fs/open.c:947 vfs_open+0x3b/0x340 fs/open.c:1079 do_open fs/namei.c:4699 [inline] path_openat+0x2e3b/0x3890 fs/namei.c:4858 do_file_open+0x23e/0x4a0 fs/namei.c:4887 do_sys_openat2+0x113/0x200 fs/open.c:1364 do_sys_open fs/open.c:1370 [inline] __do_sys_openat fs/open.c:1386 [inline] __se_sys_openat fs/open.c:1381 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1381 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #5 (&cmd->lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1590 kernel/locking/mutex.c:820 nbd_queue_rq+0xc1/0x1150 drivers/block/nbd.c:1199 blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2148 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline] blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline] __blk_mq_sched_dispatch_requests+0xd36/0x1580 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329 blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2387 blk_mq_dispatch_list+0xd11/0xe10 include/linux/spinlock.h:-1 blk_mq_flush_plug_list+0x45f/0x540 block/blk-mq.c:2997 __blk_flush_plug+0x3ed/0x4d0 block/blk-core.c:1230 blk_finish_plug block/blk-core.c:1257 [inline] __submit_bio+0x465/0x560 block/blk-core.c:649 __submit_bio_noacct_mq block/blk-core.c:722 [inline] submit_bio_noacct_nocheck+0x2f4/0xa40 block/blk-core.c:753 submit_bh fs/buffer.c:2742 [inline] block_read_full_folio+0x599/0x830 fs/buffer.c:2344 filemap_read_folio+0x12c/0x3a0 mm/filemap.c:2502 do_read_cache_folio+0x354/0x590 mm/filemap.c:4107 read_mapping_folio include/linux/pagemap.h:1017 [inline] read_part_sector+0xb6/0x2b0 block/partitions/core.c:724 adfspart_check_ICS+0xb1/0x960 block/partitions/acorn.c:356 check_partition block/partitions/core.c:143 [inline] blk_add_partitions block/partitions/core.c:591 [inline] bdev_disk_changed+0x82b/0x1780 block/partitions/core.c:695 blkdev_get_whole+0x372/0x510 block/bdev.c:756 bdev_open+0x324/0xd70 block/bdev.c:965 blkdev_open+0x461/0x600 block/fops.c:697 do_dentry_open+0x816/0x1380 fs/open.c:947 vfs_open+0x3b/0x340 fs/open.c:1079 do_open fs/namei.c:4699 [inline] path_openat+0x2e3b/0x3890 fs/namei.c:4858 do_file_open+0x23e/0x4a0 fs/namei.c:4887 do_sys_openat2+0x113/0x200 fs/open.c:1364 do_sys_open fs/open.c:1370 [inline] __do_sys_openat fs/open.c:1386 [inline] __se_sys_openat fs/open.c:1381 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1381 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #4 (set->srcu){.+.+}-{0:0}: srcu_lock_sync include/linux/srcu.h:199 [inline] __synchronize_srcu+0xc9/0x2f0 kernel/rcu/srcutree.c:1481 elevator_switch+0x1e8/0x7b0 block/elevator.c:576 elevator_change+0x2fa/0x480 block/elevator.c:681 elevator_set_default+0x375/0x440 block/elevator.c:754 blk_register_queue+0x3f3/0x4e0 block/blk-sysfs.c:987 __add_disk+0x6cb/0xe30 block/genhd.c:528 add_disk_fwnode+0xfb/0x4b0 block/genhd.c:597 add_disk include/linux/blkdev.h:794 [inline] nbd_dev_add+0x733/0xb60 drivers/block/nbd.c:1984 nbd_init+0x15f/0x1e0 drivers/block/nbd.c:2692 do_one_initcall+0x250/0x870 init/main.c:1392 do_initcall_level+0x10a/0x1a0 init/main.c:1454 do_initcalls+0x59/0xa0 init/main.c:1470 kernel_init_freeable+0x29d/0x3e0 init/main.c:1703 kernel_init+0x1d/0x1d0 init/main.c:1593 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #3 (&q->elevator_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x19d/0x1590 kernel/locking/mutex.c:820 elevator_change+0x1af/0x480 block/elevator.c:679 elevator_set_none+0xb5/0x140 block/elevator.c:769 blk_mq_elv_switch_none block/blk-mq.c:5134 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:5179 [inline] blk_mq_update_nr_hw_queues+0x5ef/0x19f0 block/blk-mq.c:5244 nbd_start_device+0x189/0xb30 drivers/block/nbd.c:1489 nbd_genl_connect+0x1597/0x1c10 drivers/block/nbd.c:2239 genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2555 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x7bb/0x940 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1899 sock_sendmsg_nosec net/socket.c:787 [inline] __sock_sendmsg net/socket.c:802 [inline] ____sys_sendmsg+0x9b9/0xa20 net/socket.c:2699 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2753 __sys_sendmsg net/socket.c:2785 [inline] __do_sys_sendmsg net/socket.c:2790 [inline] __se_sys_sendmsg net/socket.c:2788 [inline] __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2788 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (&q->q_usage_counter(io)#49){++++}-{0:0}: blk_alloc_queue+0x544/0x690 block/blk-core.c:461 blk_mq_alloc_queue block/blk-mq.c:4453 [inline] __blk_mq_alloc_disk+0x194/0x390 block/blk-mq.c:4500 nbd_dev_add+0x494/0xb60 drivers/block/nbd.c:1954 nbd_init+0x15f/0x1e0 drivers/block/nbd.c:2692 do_one_initcall+0x250/0x870 init/main.c:1392 do_initcall_level+0x10a/0x1a0 init/main.c:1454 do_initcalls+0x59/0xa0 init/main.c:1470 kernel_init_freeable+0x29d/0x3e0 init/main.c:1703 kernel_init+0x1d/0x1d0 init/main.c:1593 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4320 [inline] fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4334 might_alloc include/linux/sched/mm.h:317 [inline] slab_pre_alloc_hook mm/slub.c:4521 [inline] slab_alloc_node mm/slub.c:4876 [inline] kmem_cache_alloc_noprof+0x40/0x650 mm/slub.c:4906 mt_alloc_one lib/maple_tree.c:139 [inline] mas_alloc_nodes+0x291/0x350 lib/maple_tree.c:1089 mas_preallocate+0x2cf/0x630 lib/maple_tree.c:4961 vma_iter_prealloc mm/vma.h:577 [inline] vma_link+0x123/0x470 mm/vma.c:1849 insert_vm_struct+0x1bf/0x290 mm/vma.c:3325 create_init_stack_vma+0x5c1/0x9b0 mm/vma_exec.c:147 bprm_mm_init fs/exec.c:274 [inline] alloc_bprm+0x46f/0x5a0 fs/exec.c:1457 class_bprm_constructor fs/exec.c:1467 [inline] kernel_execve+0x85/0x9b0 fs/exec.c:1859 try_to_run_init_process+0x13/0x60 init/main.c:1521 kernel_init+0xad/0x1d0 init/main.c:1649 ret_from_fork+0x514/0xb70 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+0x1520/0x2cd0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 gup_fast_fallback+0x226/0x20d0 mm/gup.c:3193 __iov_iter_get_pages_alloc+0x378/0xa40 lib/iov_iter.c:1091 iov_iter_get_pages2+0x5e/0xa0 lib/iov_iter.c:1137 sk_msg_zerocopy_from_iter+0x21b/0x8c0 net/core/skmsg.c:328 tls_sw_sendmsg_locked net/tls/tls_sw.c:1150 [inline] tls_sw_sendmsg+0xa19/0x2400 net/tls/tls_sw.c:1302 sock_sendmsg_nosec net/socket.c:787 [inline] __sock_sendmsg net/socket.c:802 [inline] __sys_sendto+0x4a3/0x710 net/socket.c:2266 __do_sys_sendto net/socket.c:2273 [inline] __se_sys_sendto net/socket.c:2269 [inline] __x64_sys_sendto+0xde/0x100 net/socket.c:2269 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 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 --> &nsock->tx_lock --> sk_lock-AF_INET6 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sk_lock-AF_INET6); lock(&nsock->tx_lock); lock(sk_lock-AF_INET6); rlock(&mm->mmap_lock); *** DEADLOCK *** 2 locks held by syz.1.2126/13673: #0: ffff88802bddb4e8 (&ctx->tx_lock){+.+.}-{4:4}, at: tls_sw_sendmsg+0x12e/0x2400 net/tls/tls_sw.c:1298 #1: ffff8880359d8fe0 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline] #1: ffff8880359d8fe0 (sk_lock-AF_INET6){+.+.}-{0:0}, at: tls_sw_sendmsg+0x15e/0x2400 net/tls/tls_sw.c:1301 stack backtrace: CPU: 1 UID: 0 PID: 13673 Comm: syz.1.2126 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 Call Trace: <TASK> 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+0x1520/0x2cd0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 gup_fast_fallback+0x226/0x20d0 mm/gup.c:3193 __iov_iter_get_pages_alloc+0x378/0xa40 lib/iov_iter.c:1091 iov_iter_get_pages2+0x5e/0xa0 lib/iov_iter.c:1137 sk_msg_zerocopy_from_iter+0x21b/0x8c0 net/core/skmsg.c:328 tls_sw_sendmsg_locked net/tls/tls_sw.c:1150 [inline] tls_sw_sendmsg+0xa19/0x2400 net/tls/tls_sw.c:1302 sock_sendmsg_nosec net/socket.c:787 [inline] __sock_sendmsg net/socket.c:802 [inline] __sys_sendto+0x4a3/0x710 net/socket.c:2266 __do_sys_sendto net/socket.c:2273 [inline] __se_sys_sendto net/socket.c:2269 [inline] __x64_sys_sendto+0xde/0x100 net/socket.c:2269 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f704335d68e Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08 RSP: 002b:00007f70441ffe88 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffffffffffffffda RBX: 00007f70442016c0 RCX: 00007f704335d68e RDX: 0000000000000020 RSI: 00007f7044200000 RDI: 0000000000000003 RBP: 0000000000000000 R08: 00007f70441fff04 R09: 000000000000000c R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003 R13: 00007f70441fff58 R14: 00007f7044200000 R15: 0000000000000000 </TASK>

Crashes (9):
Time	Kernel	Commit	Syzkaller	Config	Log	Report	VM info	Assets (help?)	Manager	Title
2026/06/14 08:08	net	a4004aa0debf	1d2f3589	.config	console log	report	info	[disk image] [vmlinux] [kernel image]	ci-upstream-net-this-kasan-gce	possible deadlock in gup_fast_fallback
2026/05/27 15:37	net	dd433671fef3	769cbc61	.config	console log	report	info	[disk image] [vmlinux] [kernel image]	ci-upstream-net-this-kasan-gce	possible deadlock in gup_fast_fallback
2026/05/14 13:41	net-next	1f8fd0fe5641	6ccb967e	.config	console log	report	info	[disk image] [vmlinux] [kernel image]	ci-upstream-net-kasan-gce	possible deadlock in gup_fast_fallback
2026/05/14 08:06	net-next	1f8fd0fe5641	6ccb967e	.config	console log	report	info	[disk image] [vmlinux] [kernel image]	ci-upstream-net-kasan-gce	possible deadlock in gup_fast_fallback
2026/05/13 07:06	net-next	543bdc1578cd	a0949470	.config	console log	report	info	[disk image] [vmlinux] [kernel image]	ci-upstream-net-kasan-gce	possible deadlock in gup_fast_fallback
2026/05/11 16:33	net-next	63751099502d	e6eb7c0b	.config	console log	report	info	[disk image] [vmlinux] [kernel image]	ci-upstream-net-kasan-gce	possible deadlock in gup_fast_fallback
2026/05/11 13:17	net-next	63751099502d	e6eb7c0b	.config	console log	report	info	[disk image] [vmlinux] [kernel image]	ci-upstream-net-kasan-gce	possible deadlock in gup_fast_fallback
2026/05/11 02:41	net-next	a93245816556	29233ece	.config	console log	report	info	[disk image] [vmlinux] [kernel image]	ci-upstream-net-kasan-gce	possible deadlock in gup_fast_fallback
2026/05/08 12:41	net-next	6a4c4656b0d2	5633175a	.config	console log	report	info	[disk image] [vmlinux] [kernel image]	ci-upstream-net-kasan-gce	possible deadlock in gup_fast_fallback

Crashes (9):

Assets (help?)