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Filipe Manana e1b18b9590 btrfs: fix transaction abort when snapshotting received subvolumes
Currently a user can trigger a transaction abort by snapshotting a
previously received snapshot a bunch of times until we reach a
BTRFS_UUID_KEY_RECEIVED_SUBVOL item overflow (the maximum item size we
can store in a leaf). This is very likely not common in practice, but
if it happens, it turns the filesystem into RO mode. The snapshot, send
and set_received_subvol and subvol_setflags (used by receive) don't
require CAP_SYS_ADMIN, just inode_owner_or_capable(). A malicious user
could use this to turn a filesystem into RO mode and disrupt a system.

Reproducer script:

  $ cat test.sh
  #!/bin/bash

  DEV=/dev/sdi
  MNT=/mnt/sdi

  # Use smallest node size to make the test faster.
  mkfs.btrfs -f --nodesize 4K $DEV
  mount $DEV $MNT

  # Create a subvolume and set it to RO so that it can be used for send.
  btrfs subvolume create $MNT/sv
  touch $MNT/sv/foo
  btrfs property set $MNT/sv ro true

  # Send and receive the subvolume into snaps/sv.
  mkdir $MNT/snaps
  btrfs send $MNT/sv | btrfs receive $MNT/snaps

  # Now snapshot the received subvolume, which has a received_uuid, a
  # lot of times to trigger the leaf overflow.
  total=500
  for ((i = 1; i <= $total; i++)); do
      echo -ne "\rCreating snapshot $i/$total"
      btrfs subvolume snapshot -r $MNT/snaps/sv $MNT/snaps/sv_$i > /dev/null
  done
  echo

  umount $MNT

When running the test:

  $ ./test.sh
  (...)
  Create subvolume '/mnt/sdi/sv'
  At subvol /mnt/sdi/sv
  At subvol sv
  Creating snapshot 496/500ERROR: Could not create subvolume: Value too large for defined data type
  Creating snapshot 497/500ERROR: Could not create subvolume: Read-only file system
  Creating snapshot 498/500ERROR: Could not create subvolume: Read-only file system
  Creating snapshot 499/500ERROR: Could not create subvolume: Read-only file system
  Creating snapshot 500/500ERROR: Could not create subvolume: Read-only file system

And in dmesg/syslog:

  $ dmesg
  (...)
  [251067.627338] BTRFS warning (device sdi): insert uuid item failed -75 (0x4628b21c4ac8d898, 0x2598bee2b1515c91) type 252!
  [251067.629212] ------------[ cut here ]------------
  [251067.630033] BTRFS: Transaction aborted (error -75)
  [251067.630871] WARNING: fs/btrfs/transaction.c:1907 at create_pending_snapshot.cold+0x52/0x465 [btrfs], CPU#10: btrfs/615235
  [251067.632851] Modules linked in: btrfs dm_zero (...)
  [251067.644071] CPU: 10 UID: 0 PID: 615235 Comm: btrfs Tainted: G        W           6.19.0-rc8-btrfs-next-225+ #1 PREEMPT(full)
  [251067.646165] Tainted: [W]=WARN
  [251067.646733] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014
  [251067.648735] RIP: 0010:create_pending_snapshot.cold+0x55/0x465 [btrfs]
  [251067.649984] Code: f0 48 0f (...)
  [251067.653313] RSP: 0018:ffffce644908fae8 EFLAGS: 00010292
  [251067.653987] RAX: 00000000ffffff01 RBX: ffff8e5639e63a80 RCX: 00000000ffffffd3
  [251067.655042] RDX: ffff8e53faa76b00 RSI: 00000000ffffffb5 RDI: ffffffffc0919750
  [251067.656077] RBP: ffffce644908fbd8 R08: 0000000000000000 R09: ffffce644908f820
  [251067.657068] R10: ffff8e5adc1fffa8 R11: 0000000000000003 R12: ffff8e53c0431bd0
  [251067.658050] R13: ffff8e5414593600 R14: ffff8e55efafd000 R15: 00000000ffffffb5
  [251067.659019] FS:  00007f2a4944b3c0(0000) GS:ffff8e5b27dae000(0000) knlGS:0000000000000000
  [251067.660115] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  [251067.660943] CR2: 00007ffc5aa57898 CR3: 00000005813a2003 CR4: 0000000000370ef0
  [251067.661972] Call Trace:
  [251067.662292]  <TASK>
  [251067.662653]  create_pending_snapshots+0x97/0xc0 [btrfs]
  [251067.663413]  btrfs_commit_transaction+0x26e/0xc00 [btrfs]
  [251067.664257]  ? btrfs_qgroup_convert_reserved_meta+0x35/0x390 [btrfs]
  [251067.665238]  ? _raw_spin_unlock+0x15/0x30
  [251067.665837]  ? record_root_in_trans+0xa2/0xd0 [btrfs]
  [251067.666531]  btrfs_mksubvol+0x330/0x580 [btrfs]
  [251067.667145]  btrfs_mksnapshot+0x74/0xa0 [btrfs]
  [251067.667827]  __btrfs_ioctl_snap_create+0x194/0x1d0 [btrfs]
  [251067.668595]  btrfs_ioctl_snap_create_v2+0x107/0x130 [btrfs]
  [251067.669479]  btrfs_ioctl+0x1580/0x2690 [btrfs]
  [251067.670093]  ? count_memcg_events+0x6d/0x180
  [251067.670849]  ? handle_mm_fault+0x1a0/0x2a0
  [251067.671652]  __x64_sys_ioctl+0x92/0xe0
  [251067.672406]  do_syscall_64+0x50/0xf20
  [251067.673129]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
  [251067.674096] RIP: 0033:0x7f2a495648db
  [251067.674812] Code: 00 48 89 (...)
  [251067.678227] RSP: 002b:00007ffc5aa57840 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
  [251067.679691] RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f2a495648db
  [251067.681145] RDX: 00007ffc5aa588b0 RSI: 0000000050009417 RDI: 0000000000000004
  [251067.682511] RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000
  [251067.683842] R10: 000000000000000a R11: 0000000000000246 R12: 00007ffc5aa59910
  [251067.685176] R13: 00007ffc5aa588b0 R14: 0000000000000004 R15: 0000000000000006
  [251067.686524]  </TASK>
  [251067.686972] ---[ end trace 0000000000000000 ]---
  [251067.687890] BTRFS: error (device sdi state A) in create_pending_snapshot:1907: errno=-75 unknown
  [251067.689049] BTRFS info (device sdi state EA): forced readonly
  [251067.689054] BTRFS warning (device sdi state EA): Skipping commit of aborted transaction.
  [251067.690119] BTRFS: error (device sdi state EA) in cleanup_transaction:2043: errno=-75 unknown
  [251067.702028] BTRFS info (device sdi state EA): last unmount of filesystem 46dc3975-30a2-4a69-a18f-418b859cccda

Fix this by ignoring -EOVERFLOW errors from btrfs_uuid_tree_add() in the
snapshot creation code when attempting to add the
BTRFS_UUID_KEY_RECEIVED_SUBVOL item. This is OK because it's not critical
and we are still able to delete the snapshot, as snapshot/subvolume
deletion ignores if a BTRFS_UUID_KEY_RECEIVED_SUBVOL is missing (see
inode.c:btrfs_delete_subvolume()). As for send/receive, we can still do
send/receive operations since it always peeks the first root ID in the
existing BTRFS_UUID_KEY_RECEIVED_SUBVOL (it could peek any since all
snapshots have the same content), and even if the key is missing, it
falls back to searching by BTRFS_UUID_KEY_SUBVOL key.

A test case for fstests will be sent soon.

Fixes: dd5f9615fc ("Btrfs: maintain subvolume items in the UUID tree")
CC: stable@vger.kernel.org # 3.12+
Reviewed-by: Boris Burkov <boris@bur.io>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
History 2026-03-03 17:03:59 +01:00
arch RISC-V updates for v6.19-rc8 2026-01-30 16:57:36 -08:00
block block-6.19-20260122 2026-01-23 12:53:56 -08:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec 2026-01-20 14:38:48 +08:00
Documentation sound fixes for 6.19-rc8 2026-01-31 08:52:41 -08:00
drivers SCSI fixes on 20260201 2026-02-01 11:24:53 -08:00
fs btrfs: fix transaction abort when snapshotting received subvolumes 2026-03-03 17:03:59 +01:00
include btrfs: allow mounting filesystems with remap-tree incompat flag 2026-02-03 07:54:35 +01:00
init Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
io_uring io_uring-6.19-20260122 2026-01-23 12:51:00 -08:00
ipc Significant patch series in this pull request: 2025-12-06 14:01:20 -08:00
kernel Fix a race in the user-callchains code. 2026-02-01 10:47:21 -08:00
lib mm/zone_device: reinitialize large zone device private folios 2026-01-26 19:03:48 -08:00
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
mm 16 hotfixes. 9 are cc:stable, 12 are for MM. 2026-01-29 11:09:13 -08:00
net net: fix segmentation of forwarding fraglist GRO 2026-01-29 14:40:12 +01:00
rust Rust fixes for v6.19 2026-01-30 16:15:59 -08:00
samples samples/ftrace: Adjust LoongArch register restore order in direct calls 2025-12-31 15:19:25 +08:00
scripts Miscellaneous objtool fixes: 2026-02-01 10:27:43 -08:00
security keys/trusted_keys: fix handle passed to tpm_buf_append_name during unseal 2026-01-25 19:03:45 +02:00
sound ASoC: Fixes for v6.19 2026-01-29 13:58:06 +01:00
tools Miscellaneous objtool fixes: 2026-02-01 10:27:43 -08:00
usr initramfs: add gen_init_cpio to hostprogs unconditionally 2025-11-26 21:55:40 +01:00
virt KVM fixes for 6.19-rc1 2025-12-18 18:38:45 +01:00
.clang-format s390/pci: Fix cyclic dead-lock in zpci_zdev_put() and zpci_scan_devices() 2025-12-14 11:03:58 +01:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: kbuild: add proc macro library support 2025-11-24 17:15:36 +01:00
.mailmap 16 hotfixes. 9 are cc:stable, 12 are for MM. 2026-01-29 11:09:13 -08:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS nfc: MAINTAINERS: Orphan the NFC and look for new maintainers 2026-01-20 16:05:38 -08:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS Including fixes from bluetooth, CAN and wireless. 2026-01-29 10:21:52 -08:00
Makefile Linux 6.19-rc8 2026-02-01 14:01:13 -08:00
README README: restructure with role-based documentation and guidelines 2025-11-29 08:40:33 -07:00

Linux kernel
============

The Linux kernel is the core of any Linux operating system. It manages hardware,
system resources, and provides the fundamental services for all other software.

Quick Start
-----------

* Report a bug: See Documentation/admin-guide/reporting-issues.rst
* Get the latest kernel: https://kernel.org
* Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst
* Join the community: https://lore.kernel.org/

Essential Documentation
-----------------------

All users should be familiar with:

* Building requirements: Documentation/process/changes.rst
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* License: See COPYING

Documentation can be built with make htmldocs or viewed online at:
https://www.kernel.org/doc/html/latest/


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============

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* New Kernel Developer - Getting started with kernel development
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* System Administrator - Configuring and troubleshooting
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==================

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--------------------

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-------------------

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* Researcher Guidelines: Documentation/process/researcher-guidelines.rst
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---------------

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-----------------------------

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* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
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--------------------

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----------

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---------------

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-----------------------

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* ABI Documentation: Documentation/ABI/README
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=========================

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