In the Linux kernel, the following vulnerability has been resolved:
btrfs: initialize inode mapping flags for cached inodes
[BUG]
When running generic/795 with 8K block size, 4K page size, the test
always fails, triggering some ASSERT()s related to folio size:
795 (241074): drop_caches: 3
assertion failed: IS_ALIGNED(start, blocksize) && IS_ALIGNED(end + 1, blocksize), in extent_io.c:1404 (blocksize=8192 root=262 ino=258 start=16826368 end=16830463 mapping min order=0)
------------[ cut here ]------------
kernel BUG at extent_io.c:1404!
Oops: invalid opcode: 0000 [#1] SMP
CPU: 8 UID: 0 PID: 241105 Comm: fsstress Tainted: G OE 7.2.0-rc5-custom+ #442 PREEMPT(full) f4bfb352566f3949f29c233ce6f735050a03b245
Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022
RIP: 0010:assert_folio_range.cold+0x3d/0x3f [btrfs]
Call Trace:
btrfs_read_folio+0x9e/0x170 [btrfs 4cd1dd93b341b8ef766643f9512f4a86259567a3]
prepare_one_folio.constprop.0+0x104/0x2a0 [btrfs 4cd1dd93b341b8ef766643f9512f4a86259567a3]
btrfs_buffered_write+0x285/0xa50 [btrfs 4cd1dd93b341b8ef766643f9512f4a86259567a3]
btrfs_do_write_iter+0x1aa/0x210 [btrfs 4cd1dd93b341b8ef766643f9512f4a86259567a3]
iter_file_splice_write+0x31a/0x540
direct_splice_actor+0x53/0x170
splice_direct_to_actor+0xe9/0x240
do_splice_direct+0x76/0xb0
vfs_copy_file_range+0x1fd/0x630
__x64_sys_copy_file_range+0xf9/0x220
do_syscall_64+0xe1/0x790
entry_SYSCALL_64_after_hwframe+0x4b/0x53
---[ end trace 0000000000000000 ]---
The ASSERT() itself is added by a later patch.
The crash is triggered with that new debug patch, and without this fix.
[CAUSE]
In the above case, the start 16826368 is properly 8K aligned, but the
end (16830463 + 1) is not 8K aligned.
Furthermore the mapping's minimal folio order is 0, not the expected 1
for 8K block size with 4K page size.
So this means some inodes do not have btrfs_set_inode_mapping_order()
called on it.
The missing btrfs_set_inode_mapping_order() call happens for cached
inodes, through the following events:
- btrfs_create_new_inode() called for inode X
Which properly sets minimal folio order for the VFS inode.
- btrfs_update_inode() called for inode X
Which calls btrfs_delayed_update_inode() to create a delayed_node
into root->delayed_nodes xarray.
- Drop cache/memory pressure, evicting in-memory inode X
Which evicted the inode X, but delayed_node is still in
root->delayed_nodes for future reuse.
- btrfs_iget() for inode X called again
btrfs_iget()
|- btrfs_iget_locked()
| |- iget5_locked_rcu()
| Which creates a new vfs_inode for btrfs, whose mapping still
| has the minimal order as 0.
|
|- btrfs_read_locked_inode()
|- btrfs_fill_inode()
| |- btrfs_get_delayed_node()
| Which found out the previous node, and use that delayed
| node to initialize the new inode.
|
|- filled = true;
|- if (filled) goto cache_index;
Which skips the btrfs_update_inode_mapping_flags() and
btrfs_set_inode_mapping_order() calls.
So the inode still has minimal folio order set as 0, not
the required 1.
Thus later page cache read will get a folio whose size is smaller than
block size, as the mapping has its minimal folio order set as 0 not 1,
then trigger the ASSERT().
[FIX]
Move the btrfs_update_inode_mapping_flags() and
btrfs_set_inode_mapping_order() calls under cache_index label,
so that the mapping flags and minimal folio order is always set
no matter if we have a cached inode.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (8.8): severity, escalated by confirmed exploitation. This CVE's 8.8 is its impact severity (EG Severity), not escalated.
- EG Severity
- 8.8 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.6% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-24). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it