kernel/linux.git/drivers/block/nbd.c, branch v7.2-rc1

nbd: don't warn when reclassifying a busy socket lock

2026-06-22T21:56:53+00:00

nbd_reclassify_socket() warns via WARN_ON_ONCE() if the socket lock is held at the point of reclassification. That assertion was copied from nvme-tcp, where the socket is created internally by the kernel (sock_create_kern()) and is never visible to user space, so the lock is guaranteed to be free. NBD is different: the socket is looked up from a user-supplied fd in nbd_get_socket(), and user space retains that fd. A concurrent syscall on the same socket (or softirq processing taking bh_lock_sock() on a connected TCP socket) can legitimately hold the lock at the instant NBD reclassifies it. sock_allow_reclassification() then returns false and the WARN_ON_ONCE() fires, which turns into a crash under panic_on_warn. This is reachable by simply racing NBD_CMD_CONNECT against socket activity on the same fd, as reported by syzbot. Hitting a held lock here is expected for an externally owned socket and is not a kernel bug, so skip reclassification silently instead of warning. Reclassification is a lockdep-only annotation, so skipping it in the rare racing case is harmless. Reported-by: syzbot+6b85d1e39a5b8ed9a954@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=6b85d1e39a5b8ed9a954 Fixes: d532cddb6c60 ("nbd: Reclassify sockets to avoid lockdep circular dependency") Signed-off-by: Deepanshu Kartikey Acked-by: Eric Dumazet Link: https://patch.msgid.link/20260621235255.66015-1-kartikey406@gmail.com Signed-off-by: Jens Axboe

nbd: Reclassify sockets to avoid lockdep circular dependency

2026-06-13T12:34:34+00:00

syzbot reported a possible circular locking dependency in udp_sendmsg() where fs_reclaim can be triggered while holding sk_lock, and fs_reclaim can eventually depend on another sk_lock (e.g., if NBD is used for swap or writeback and NBD uses TLS/TCP which acquires sk_lock). Since the UDP socket and the NBD TCP/TLS socket are different, this is a false positive. Fix this by reclassifying NBD sockets to a separate lock class when they are added to the NBD device. This is similar to what nvme-tcp and other network block devices do. Fixes: ffa1e7ada456 ("block: Make request_queue lockdep splats show up earlier") Reported-by: syzbot+607cdcf978b3e79da878@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/6a2cdafe.428ffe26.258b27.0161.GAE@google.com/T/#u Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260613042619.1108126-1-edumazet@google.com Signed-off-by: Jens Axboe

block: switch numa_node to int in blk_mq_hw_ctx and init_request

2026-05-26T17:01:55+00:00

numa_node in blk_mq_hw_ctx and the matching argument of blk_mq_ops::init_request can be NUMA_NO_NODE (-1). Declared as unsigned int, NUMA_NO_NODE becomes UINT_MAX and walks off nvme_dev::descriptor_pools[] on CONFIG_NUMA=n [1]. Switch the field and the callback prototype to int and update all in-tree init_request implementations. No functional change: cpu_to_node(), kmalloc_node() and blk_alloc_flush_queue() already take int. Link: https://lore.kernel.org/linux-nvme/20260522150628.399288-1-mateusz.nowicki@posteo.net/ [1] Link: https://lore.kernel.org/linux-nvme/20260309062840.2937858-2-iam@sung-woo.kim/ Suggested-by: Caleb Sander Mateos Suggested-by: Sung-woo Kim Signed-off-by: Mateusz Nowicki Reviewed-by: Christoph Hellwig Link: https://patch.msgid.link/20260523125210.272274-1-mateusz.nowicki@posteo.net Signed-off-by: Jens Axboe

Convert 'alloc_obj' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51+00:00

This was done entirely with mindless brute force, using git grep -l '\

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

Merge tag 'for-6.19/block-20251201' of git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux

2025-12-04T03:26:18+00:00

Pull block updates from Jens Axboe: - Fix head insertion for mq-deadline, a regression from when priority support was added - Series simplifying and improving the ublk user copy code - Various ublk related cleanups - Fixup REQ_NOWAIT handling in loop/zloop, clearing NOWAIT when the request is punted to a thread for handling - Merge and then later revert loop dio nowait support, as it ended up causing excessive stack usage for when the inline issue code needs to dip back into the full file system code - Improve auto integrity code, making it less deadlock prone - Speedup polled IO handling, but manually managing the hctx lookups - Fixes for blk-throttle for SSD devices - Small series with fixes for the S390 dasd driver - Add support for caching zones, avoiding unnecessary report zone queries - MD pull requests via Yu: - fix null-ptr-dereference regression for dm-raid0 - fix IO hang for raid5 when array is broken with IO inflight - remove legacy 1s delay to speed up system shutdown - change maintainer's email address - data can be lost if array is created with different lbs devices, fix this problem and record lbs of the array in metadata - fix rcu protection for md_thread - fix mddev kobject lifetime regression - enable atomic writes for md-linear - some cleanups - bcache updates via Coly - remove useless discard and cache device code - improve usage of per-cpu workqueues - Reorganize the IO scheduler switching code, fixing some lockdep reports as well - Improve the block layer P2P DMA support - Add support to the block tracing code for zoned devices - Segment calculation improves, and memory alignment flexibility improvements - Set of prep and cleanups patches for ublk batching support. The actual batching hasn't been added yet, but helps shrink down the workload of getting that patchset ready for 6.20 - Fix for how the ps3 block driver handles segments offsets - Improve how block plugging handles batch tag allocations - nbd fixes for use-after-free of the configuration on device clear/put - Set of improvements and fixes for zloop - Add Damien as maintainer of the block zoned device code handling - Various other fixes and cleanups * tag 'for-6.19/block-20251201' of git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux: (162 commits) block/rnbd: correct all kernel-doc complaints blk-mq: use queue_hctx in blk_mq_map_queue_type md: remove legacy 1s delay in md_notify_reboot md/raid5: fix IO hang when array is broken with IO inflight md: warn about updating super block failure md/raid0: fix NULL pointer dereference in create_strip_zones() for dm-raid sbitmap: fix all kernel-doc warnings ublk: add helper of __ublk_fetch() ublk: pass const pointer to ublk_queue_is_zoned() ublk: refactor auto buffer register in ublk_dispatch_req() ublk: add `union ublk_io_buf` with improved naming ublk: add parameter `struct io_uring_cmd *` to ublk_prep_auto_buf_reg() kfifo: add kfifo_alloc_node() helper for NUMA awareness blk-mq: fix potential uaf for 'queue_hw_ctx' blk-mq: use array manage hctx map instead of xarray ublk: prevent invalid access with DEBUG s390/dasd: Use scnprintf() instead of sprintf() s390/dasd: Move device name formatting into separate function s390/dasd: Remove unnecessary debugfs_create() return checks s390/dasd: Fix gendisk parent after copy pair swap ...

nbd: defer config unlock in nbd_genl_connect

2025-11-11T14:50:15+00:00

There is one use-after-free warning when running NBD_CMD_CONNECT and NBD_CLEAR_SOCK: nbd_genl_connect nbd_alloc_and_init_config // config_refs=1 nbd_start_device // config_refs=2 set NBD_RT_HAS_CONFIG_REF open nbd // config_refs=3 recv_work done // config_refs=2 NBD_CLEAR_SOCK // config_refs=1 close nbd // config_refs=0 refcount_inc -> uaf ------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: CPU: 24 PID: 1014 at lib/refcount.c:25 refcount_warn_saturate+0x12e/0x290 nbd_genl_connect+0x16d0/0x1ab0 genl_family_rcv_msg_doit+0x1f3/0x310 genl_rcv_msg+0x44a/0x790 The issue can be easily reproduced by adding a small delay before refcount_inc(&nbd->config_refs) in nbd_genl_connect(): mutex_unlock(&nbd->config_lock); if (!ret) { set_bit(NBD_RT_HAS_CONFIG_REF, &config->runtime_flags); + printk("before sleep\n"); + mdelay(5 * 1000); + printk("after sleep\n"); refcount_inc(&nbd->config_refs); nbd_connect_reply(info, nbd->index); } Fixes: e46c7287b1c2 ("nbd: add a basic netlink interface") Signed-off-by: Zheng Qixing Reviewed-by: Yu Kuai Signed-off-by: Jens Axboe

nbd: defer config put in recv_work

2025-11-08T13:37:54+00:00

There is one uaf issue in recv_work when running NBD_CLEAR_SOCK and NBD_CMD_RECONFIGURE: nbd_genl_connect // conf_ref=2 (connect and recv_work A) nbd_open // conf_ref=3 recv_work A done // conf_ref=2 NBD_CLEAR_SOCK // conf_ref=1 nbd_genl_reconfigure // conf_ref=2 (trigger recv_work B) close nbd // conf_ref=1 recv_work B config_put // conf_ref=0 atomic_dec(&config->recv_threads); -> UAF Or only running NBD_CLEAR_SOCK: nbd_genl_connect // conf_ref=2 nbd_open // conf_ref=3 NBD_CLEAR_SOCK // conf_ref=2 close nbd nbd_release config_put // conf_ref=1 recv_work config_put // conf_ref=0 atomic_dec(&config->recv_threads); -> UAF Commit 87aac3a80af5 ("nbd: call nbd_config_put() before notifying the waiter") moved nbd_config_put() to run before waking up the waiter in recv_work, in order to ensure that nbd_start_device_ioctl() would not be woken up while nbd->task_recv was still uncleared. However, in nbd_start_device_ioctl(), after being woken up it explicitly calls flush_workqueue() to make sure all current works are finished. Therefore, there is no need to move the config put ahead of the wakeup. Move nbd_config_put() to the end of recv_work, so that the reference is held for the whole lifetime of the worker thread. This makes sure the config cannot be freed while recv_work is still running, even if clear + reconfigure interleave. In addition, we don't need to worry about recv_work dropping the last nbd_put (which causes deadlock): path A (netlink with NBD_CFLAG_DESTROY_ON_DISCONNECT): connect // nbd_refs=1 (trigger recv_work) open nbd // nbd_refs=2 NBD_CLEAR_SOCK close nbd nbd_release nbd_disconnect_and_put flush_workqueue // recv_work done nbd_config_put nbd_put // nbd_refs=1 nbd_put // nbd_refs=0 queue_work path B (netlink without NBD_CFLAG_DESTROY_ON_DISCONNECT): connect // nbd_refs=2 (trigger recv_work) open nbd // nbd_refs=3 NBD_CLEAR_SOCK // conf_refs=2 close nbd nbd_release nbd_config_put // conf_refs=1 nbd_put // nbd_refs=2 recv_work done // conf_refs=0, nbd_refs=1 rmmod // nbd_refs=0 Reported-by: syzbot+56fbf4c7ddf65e95c7cc@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/6907edce.a70a0220.37351b.0014.GAE@google.com/T/ Fixes: 87aac3a80af5 ("nbd: make the config put is called before the notifying the waiter") Depends-on: e2daec488c57 ("nbd: Fix hungtask when nbd_config_put") Signed-off-by: Zheng Qixing Signed-off-by: Jens Axboe

nbd: don't copy kernel creds

2025-11-04T11:36:16+00:00

No need to copy kernel credentials. Link: https://patch.msgid.link/20251103-work-creds-init_cred-v1-6-cb3ec8711a6a@kernel.org Reviewed-by: Jens Axboe Signed-off-by: Christian Brauner

nbd: override creds to kernel when calling sock_{send,recv}msg()

2025-10-20T15:27:58+00:00

sock_{send,recv}msg() internally calls security_socket_{send,recv}msg(), which does security checks (e.g. SELinux) for socket access against the current task. However, _sock_xmit() in drivers/block/nbd.c may be called indirectly from a userspace syscall, where the NBD socket access would be incorrectly checked against the calling userspace task (which simply tries to read/write a file that happens to reside on an NBD device). To fix this, temporarily override creds to kernel ones before calling the sock_*() functions. This allows the security modules to recognize this as internal access by the kernel, which will normally be allowed. A way to trigger the issue is to do the following (on a system with SELinux set to enforcing): ### Create nbd device: truncate -s 256M /tmp/testfile nbd-server localhost:10809 /tmp/testfile ### Connect to the nbd server: nbd-client localhost ### Create mdraid array mdadm --create -l 1 -n 2 /dev/md/testarray /dev/nbd0 missing After these steps, assuming the SELinux policy doesn't allow the unexpected access pattern, errors will be visible on the kernel console: [ 142.204243] nbd0: detected capacity change from 0 to 524288 [ 165.189967] md: async del_gendisk mode will be removed in future, please upgrade to mdadm-4.5+ [ 165.252299] md/raid1:md127: active with 1 out of 2 mirrors [ 165.252725] md127: detected capacity change from 0 to 522240 [ 165.255434] block nbd0: Send control failed (result -13) [ 165.255718] block nbd0: Request send failed, requeueing [ 165.256006] block nbd0: Dead connection, failed to find a fallback [ 165.256041] block nbd0: Receive control failed (result -32) [ 165.256423] block nbd0: shutting down sockets [ 165.257196] I/O error, dev nbd0, sector 2048 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2 [ 165.257736] Buffer I/O error on dev md127, logical block 0, async page read [ 165.258263] I/O error, dev nbd0, sector 2048 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2 [ 165.259376] Buffer I/O error on dev md127, logical block 0, async page read [ 165.259920] I/O error, dev nbd0, sector 2048 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2 [ 165.260628] Buffer I/O error on dev md127, logical block 0, async page read [ 165.261661] ldm_validate_partition_table(): Disk read failed. [ 165.262108] I/O error, dev nbd0, sector 2048 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2 [ 165.262769] Buffer I/O error on dev md127, logical block 0, async page read [ 165.263697] I/O error, dev nbd0, sector 2048 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2 [ 165.264412] Buffer I/O error on dev md127, logical block 0, async page read [ 165.265412] I/O error, dev nbd0, sector 2048 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2 [ 165.265872] Buffer I/O error on dev md127, logical block 0, async page read [ 165.266378] I/O error, dev nbd0, sector 2048 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2 [ 165.267168] Buffer I/O error on dev md127, logical block 0, async page read [ 165.267564] md127: unable to read partition table [ 165.269581] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2 [ 165.269960] Buffer I/O error on dev nbd0, logical block 0, async page read [ 165.270316] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2 [ 165.270913] Buffer I/O error on dev nbd0, logical block 0, async page read [ 165.271253] I/O error, dev nbd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2 [ 165.271809] Buffer I/O error on dev nbd0, logical block 0, async page read [ 165.272074] ldm_validate_partition_table(): Disk read failed. [ 165.272360] nbd0: unable to read partition table [ 165.289004] ldm_validate_partition_table(): Disk read failed. [ 165.289614] nbd0: unable to read partition table The corresponding SELinux denial on Fedora/RHEL will look like this (assuming it's not silenced): type=AVC msg=audit(1758104872.510:116): avc: denied { write } for pid=1908 comm="mdadm" laddr=::1 lport=32772 faddr=::1 fport=10809 scontext=system_u:system_r:mdadm_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tclass=tcp_socket permissive=0 The respective backtrace looks like this: @security[mdadm, -13, handshake_exit+221615650 handshake_exit+221615650 handshake_exit+221616465 security_socket_sendmsg+5 sock_sendmsg+106 handshake_exit+221616150 sock_sendmsg+5 __sock_xmit+162 nbd_send_cmd+597 nbd_handle_cmd+377 nbd_queue_rq+63 blk_mq_dispatch_rq_list+653 __blk_mq_do_dispatch_sched+184 __blk_mq_sched_dispatch_requests+333 blk_mq_sched_dispatch_requests+38 blk_mq_run_hw_queue+239 blk_mq_dispatch_plug_list+382 blk_mq_flush_plug_list.part.0+55 __blk_flush_plug+241 __submit_bio+353 submit_bio_noacct_nocheck+364 submit_bio_wait+84 __blkdev_direct_IO_simple+232 blkdev_read_iter+162 vfs_read+591 ksys_read+95 do_syscall_64+92 entry_SYSCALL_64_after_hwframe+120 ]: 1 The issue has started to appear since commit 060406c61c7c ("block: add plug while submitting IO"). Cc: Ming Lei Link: https://bugzilla.redhat.com/show_bug.cgi?id=2348878 Fixes: 060406c61c7c ("block: add plug while submitting IO") Signed-off-by: Ondrej Mosnacek Acked-by: Paul Moore Acked-by: Stephen Smalley Reviewed-by: Ming Lei Tested-by: Ming Lei Signed-off-by: Jens Axboe