Medium 5.5Published Sep 25, 2026

CVE-2026-98080btrfs: do not force reloc root creation during qgroup_account_snapshot()

Updated under an hour ago (2026-10-19 10:23 UTC)

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In the Linux kernel, the following vulnerability has been resolved: btrfs: do not force reloc root creation during qgroup_account_snapshot() [BUG] When running btrfs/252 with quota enabled through MKFS_OPTIONS="-O quota", it has a high chance to trigger the following kernel warning and flips the fs RO: BTRFS info (device dm-2): relocating block group 30408704 flags metadata|dup ------------[ cut here ]------------ WARNING: fs/btrfs/extent-tree.c:879 at lookup_inline_extent_backref+0x74b/0x960 [btrfs], CPU#4: btrfs/2173 CPU: 4 UID: 0 PID: 2173 Comm: btrfs Not tainted 7.2.0-rc6-custom+ #457 PREEMPT(full) 3adc6528fb66f7a55fe1095385818e742f200aab Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022 RIP: 0010:lookup_inline_extent_backref+0x74b/0x960 [btrfs] Call Trace: <TASK> insert_inline_extent_backref+0x7c/0x160 [btrfs 32f09462c54d9c922fca74a3e4866f4aa7737b72] __btrfs_inc_extent_ref+0xa9/0x270 [btrfs 32f09462c54d9c922fca74a3e4866f4aa7737b72] __btrfs_run_delayed_refs+0x4af/0x11c0 [btrfs 32f09462c54d9c922fca74a3e4866f4aa7737b72] btrfs_run_delayed_refs+0x9d/0xf0 [btrfs 32f09462c54d9c922fca74a3e4866f4aa7737b72] create_pending_snapshot+0x39d/0xf00 [btrfs 32f09462c54d9c922fca74a3e4866f4aa7737b72] create_pending_snapshots+0x9b/0xc0 [btrfs 32f09462c54d9c922fca74a3e4866f4aa7737b72] btrfs_commit_transaction+0x280/0xeb0 [btrfs 32f09462c54d9c922fca74a3e4866f4aa7737b72] prepare_to_relocate+0x147/0x200 [btrfs 32f09462c54d9c922fca74a3e4866f4aa7737b72] relocate_block_group+0x6b/0x5e0 [btrfs 32f09462c54d9c922fca74a3e4866f4aa7737b72] btrfs_relocate_block_group+0x92c/0x2380 [btrfs 32f09462c54d9c922fca74a3e4866f4aa7737b72] btrfs_relocate_chunk+0x3f/0x1a0 [btrfs 32f09462c54d9c922fca74a3e4866f4aa7737b72] btrfs_balance+0xa2c/0x19c0 [btrfs 32f09462c54d9c922fca74a3e4866f4aa7737b72] btrfs_ioctl+0x2839/0x2d30 [btrfs 32f09462c54d9c922fca74a3e4866f4aa7737b72] __x64_sys_ioctl+0x416/0x9a0 do_syscall_64+0xe1/0x790 entry_SYSCALL_64_after_hwframe+0x4b/0x53 </TASK> ---[ end trace 0000000000000000 ]--- BTRFS info (device dm-2): leaf 4593991680 gen 233 total ptrs 175 free space 5953 owner 2 BTRFS info (device dm-2): refs 3 lock_owner 2173 current 2173 item 0 key (166772736 METADATA_ITEM 1) itemoff 16250 itemsize 33 extent refs 1 gen 222 flags 2 ref#0: tree block backref root 266 [ Skip the tree dump ] item 174 key (263225344 METADATA_ITEM 0) itemoff 10328 itemsize 33 extent refs 1 gen 162 flags 258 ref#0: tree block backref root 267 BTRFS error (device dm-2): extent item not found for insert, bytenr 179847168 num_bytes 16384 parent 4594335744 root_objectid 273 owner 0 offset 0 BTRFS error (device dm-2): failed to run delayed ref for logical 179847168 num_bytes 16384 type 182 action 1 ref_mod 1: -117 [CAUSE] The above error is showing that there is a tree reference to a metadata extent that is no longer there. With "ref_verify" mount option (requires CONFIG_BTRFS_DEBUG), there is some extra debug output: BTRFS error (device dm-2): dumping block entry [180961280 16384], num_refs 0, metadata 1, from disk 0 BTRFS error (device dm-2): root entry 256, num_refs 18446744073709551615 BTRFS error (device dm-2): root entry 273, num_refs 18446744073709551615 BTRFS error (device dm-2): Ref action 3, root 273, ref_root 273, parent 0, owner 0, offset 0, num_refs 1 btrfs_force_cow_block+0x129/0x7d0 [btrfs] btrfs_cow_block+0x10a/0x250 [btrfs] btrfs_search_slot+0x5eb/0xf40 [btrfs] btrfs_insert_empty_items+0x3a/0x70 [btrfs] insert_with_overflow+0x53/0x130 [btrfs] btrfs_insert_dir_item+0x125/0x290 [btrfs] btrfs_add_link+0xaa/0x410 [btrfs] btrfs_rename+0x5ea/0xcd0 [btrfs] btrfs_rename2+0x28/0x60 [btrfs] vfs_rename+0x5b2/0xe10 filename_renameat2+0x244/0x430 __x64_sys_rename+0x48/0x70 do_syscall_64+0xe1/0x790 entry_SYSCALL_64_after_hwframe+0x4b/0x53 ---truncated---

CVSS: 5.5 MEDIUM (v3.1, NVD)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): Not given
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Analyzed
Record last updated: Oct 19, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from 4d31778aa2fa342f5f92ca4025b293a1729161d1 before d0284d974be46a0a06068f930c84039d540ae8ed; from 4d31778aa2fa342f5f92ca4025b293a1729161d1 before 21bd77c132f18dc21c6fcdf417310d1adcf7448b; from 4d31778aa2fa342f5f92ca4025b293a1729161d1 before 7ce02d52548b672795511c2cac8da6ec79ac8877; from 4d31778aa2fa342f5f92ca4025b293a1729161d1 before 7caaae233a55e167063f4cfa3385b1a04c8bbecb; from 4d31778aa2fa342f5f92ca4025b293a1729161d1 before c4c78768d1a8ceb713693cc5524acbe984c31f3c; from 4d31778aa2fa342f5f92ca4025b293a1729161d1 before 203cbfb4fba590bd9b08bd36fa6d05b5d28923bf; from 4d31778aa2fa342f5f92ca4025b293a1729161d1 before b5d5ab5a715001dd937c920ef8c5688fd4999ba1; from 4d31778aa2fa342f5f92ca4025b293a1729161d1 before cacf35832292997018837e484283f95a9301ebf5; and 4 more ranges	CNA record
linux linux_kernel linux:linux_kernel	from 4.14.45 before 4.15; from 4.16.13 before 5.10.271; from 5.11 before 5.15.222; from 6.0 before 6.1.189; from 6.2 before 6.6.158; from 6.7 before 6.12.111; from 6.13 before 6.18.53; from 6.19 before 7.2.7; and 1 more ranges	NVD

References

https://git.kernel.org/stable/c/d0284d974be46a0a06068f930c84039d540ae8edpatch
https://git.kernel.org/stable/c/21bd77c132f18dc21c6fcdf417310d1adcf7448bpatch
https://git.kernel.org/stable/c/7ce02d52548b672795511c2cac8da6ec79ac8877patch
https://git.kernel.org/stable/c/7caaae233a55e167063f4cfa3385b1a04c8bbecbpatch
https://git.kernel.org/stable/c/c4c78768d1a8ceb713693cc5524acbe984c31f3cpatch
https://git.kernel.org/stable/c/203cbfb4fba590bd9b08bd36fa6d05b5d28923bfpatch
https://git.kernel.org/stable/c/b5d5ab5a715001dd937c920ef8c5688fd4999ba1patch
https://git.kernel.org/stable/c/cacf35832292997018837e484283f95a9301ebf5patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.