In the Linux kernel, the following vulnerability has been resolved:
dm thin: Use last transaction's pmd->root when commit failed
Recently we found a softlock up problem in dm thin pool btree lookup
code due to corrupted metadata:
Kernel panic - not syncing: softlockup: hung tasks
CPU: 7 PID: 2669225 Comm: kworker/u16:3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
Workqueue: dm-thin do_worker [dm_thin_pool]
Call Trace:
dump_stack+0x9c/0xd3
panic+0x35d/0x6b9
watchdog_timer_fn.cold+0x16/0x25
__run_hrtimer+0xa2/0x2d0
RIP: 0010:__relink_lru+0x102/0x220 [dm_bufio]
__bufio_new+0x11f/0x4f0 [dm_bufio]
new_read+0xa3/0x1e0 [dm_bufio]
dm_bm_read_lock+0x33/0xd0 [dm_persistent_data]
ro_step+0x63/0x100 [dm_persistent_data]
btree_lookup_raw.constprop.0+0x44/0x220 [dm_persistent_data]
dm_btree_lookup+0x16f/0x210 [dm_persistent_data]
dm_thin_find_block+0x12c/0x210 [dm_thin_pool]
__process_bio_read_only+0xc5/0x400 [dm_thin_pool]
process_thin_deferred_bios+0x1a4/0x4a0 [dm_thin_pool]
process_one_work+0x3c5/0x730
Following process may generate a broken btree mixed with fresh and
stale btree nodes, which could get dm thin trapped in an infinite loop
while looking up data block:
Transaction 1: pmd->root = A, A->B->C // One path in btree
pmd->root = X, X->Y->Z // Copy-up
Transaction 2: X,Z is updated on disk, Y write failed.
// Commit failed, dm thin becomes read-only.
process_bio_read_only
dm_thin_find_block
__find_block
dm_btree_lookup(pmd->root)
The pmd->root points to a broken btree, Y may contain stale node
pointing to any block, for example X, which gets dm thin trapped into
a dead loop while looking up Z.
Fix this by setting pmd->root in __open_metadata(), so that dm thin
will use the last transaction's pmd->root if commit failed.
Fetch a reproducer in [Link].
Linke: https://bugzilla.kernel.org/show_bug.cgi?id=216790
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (5.5): severity, escalated by confirmed exploitation. This CVE's 5.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 5.5 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS. 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, and whom BOD 26-04 binds: 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.
The score's inputs: 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