af_unix: Unify scc_index when finalising SCC in __unix_walk_scc().
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 6.2, 6.7, 6.18.54, 7.2.8
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
In the Linux kernel, the following vulnerability has been resolved: af_unix: Unify scc_index when finalising SCC in __unix_walk_scc(). Commit bfdb01283ee8 ("af_unix: Assign a unique index to SCC.") changed Tarjan's algorithm to update lowlink with lowlink, which is called lowpoint (unix_vertex.scc_index). unix_vertex_dead() assumes all vertices in an SCC share the same lowpoint, but this is not always true if an SCC has two or more back edges, depending on the order of DFS. For example, the graph below has two back edges from B to A and from C to B. A --> B --> C ^ | ^ | `----' `----' If DFS walks through A -> B -> C -> B (-> C -> B) -> A (-> B -> A), each index and scc_index will be updated as follows. A --> B --> C C = (3, 3) (index, scc_index) B = (2, 2) A = (1, 1) A ... B ... C C = (3, 2)<-. ^ | B = (2, 2) -' `----' A = (1, 1) A ... B ... C C = (3, 2) ^ | . . B = (2, 1)<-. `----' .... A = (1, 1) -' Then, unix_vertex_dead() thinks that B is passed to another SCC with scc_index 2, and the SCC is not garbage-collected. This does not happen if DFS walks in a different order below or starts from B. 1 3 A --> B --> C ^ | ^ | `----' `----' 2 4 Let's unify scc_index across the SCC when finalising it. Note that updating v->index was previously done in unix_scc_dead(), when called from __unix_walk_scc(), just to save one loop. Since __unix_walk_scc() now iterates over the SCC anyway, the update is moved back to __unix_walk_scc() and 'fast' argument is dropped.
Timeline
- CVE published
- Record last updated
Affected versions
- Linux Linux
From 4090fa373f0e763c43610853d2774b5979915959 · fixed in b8f71d69380a5fbc734c868acbeb560f1de1766f; From 4090fa373f0e763c43610853d2774b5979915959 · fixed in be550ee108ad80828aa61280400bedfc7e7c39d3; From 4090fa373f0e763c43610853d2774b5979915959 · fixed in 4a4263dfeabad72f95e8ab6e15146861fa4144dd; From 6.1.141 · fixed in 6.2; From 6.6.93 · fixed in 6.7
- Linux Linux
6.10
- KernelLinux
From 6.10.0 · fixed in 6.18.54; From 6.19.0 · fixed in 7.2.8