Description (CNA)
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.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 4090fa373f0e763c43610853d2774b5979915959 before b8f71d69380a5fbc734c868acbeb560f1de1766f; affected 4090fa373f0e763c43610853d2774b5979915959 before be550ee108ad80828aa61280400bedfc7e7c39d3; affected 4090fa373f0e763c43610853d2774b5979915959 before 4a4263dfeabad72f95e8ab6e15146861fa4144dd; affected 5dfd283f4651d04dbb70ceb9ae5c4a30eda3c52a; affected de7921631ff323369aa63a4324695ab54ea4047e; affected 6.1.141 before 6.2; affected 6.6.93 before 6.7 |
| Linux / Linux | affected 6.10; unaffected 0 before 6.10; unaffected 6.18.54 through 6.18.*; unaffected 7.2.8 through 7.2.*; unaffected 7.3 through * |
CWE
No CWE identifiers supplied.