Description (CNA)
In the Linux kernel, the following vulnerability has been resolved: eventpoll: Fix semi-unbounded recursion Ensure that epoll instances can never form a graph deeper than EP_MAX_NESTS+1 links. Currently, ep_loop_check_proc() ensures that the graph is loop-free and does some recursion depth checks, but those recursion depth checks don't limit the depth of the resulting tree for two reasons: - They don't look upwards in the tree. - If there are multiple downwards paths of different lengths, only one of the paths is actually considered for the depth check since commit 28d82dc1c4ed ("epoll: limit paths"). Essentially, the current recursion depth check in ep_loop_check_proc() just serves to prevent it from recursing too deeply while checking for loops. A more thorough check is done in reverse_path_check() after the new graph edge has already been created; this checks, among other things, that no paths going upwards from any non-epoll file with a length of more than 5 edges exist. However, this check does not apply to non-epoll files. As a result, it is possible to recurse to a depth of at least roughly 500, tested on v6.15. (I am unsure if deeper recursion is possible; and this may have changed with commit 8c44dac8add7 ("eventpoll: Fix priority inversion problem").) To fix it: 1. In ep_loop_check_proc(), note the subtree depth of each visited node, and use subtree depths for the total depth calculation even when a subtree has already been visited. 2. Add ep_get_upwards_depth_proc() for similarly determining the maximum depth of an upwards walk. 3. In ep_loop_check(), use these values to limit the total path length between epoll nodes to EP_MAX_NESTS edges.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e before 71379495ab70eaba19224bd71b5b9b399eb85e04; affected 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e before 1b13b033062824495554e836a1ff5f85ccf6b039; affected 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e before 2a0c0c974bea9619c6f41794775ae4b97530e0e6; affected 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e before 7a2125962c42d5336ca0495a9ce4cb38a63e9161; affected 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e before ea5f97dbdcb1651581a22bd10afd2f0dd9dc11d6; affected 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e before 3542c90797bc3ab83ebab54b737d751cf3682036; affected 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e before f2e467a48287c868818085aa35389a224d226732; affected 8216e1a0d47cae06a75c42346f19dffe14e42d57; affected 28a92748aa4bc57d35e7b079498b0ac2e7610a37; affected 7eebcd4792c5a341559aed327b6afecbb1c46402; affected 0eccd188cfeaf857a26f2d72941d27d298cf6a54; affected a72affdbb09f3f24f64ffcbbdf62c2e57c58f379; affected 2.6.32.30 before 2.6.33; affected 2.6.33.8 before 2.6.34; affected 2.6.34.10 before 2.6.35; affected 2.6.35.12 before 2.6.36; affected 2.6.37.3 before 2.6.38 |
| Linux / Linux | affected 2.6.38; unaffected 0 before 2.6.38; unaffected 5.15.190 through 5.15.*; unaffected 6.1.149 through 6.1.*; unaffected 6.6.103 through 6.6.*; unaffected 6.12.43 through 6.12.*; unaffected 6.15.11 through 6.15.*; unaffected 6.16.1 through 6.16.*; unaffected 6.17 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/71379495ab70eaba19224bd71b5b9b399eb85e04
- https://git.kernel.org/stable/c/1b13b033062824495554e836a1ff5f85ccf6b039
- https://git.kernel.org/stable/c/2a0c0c974bea9619c6f41794775ae4b97530e0e6
- https://git.kernel.org/stable/c/7a2125962c42d5336ca0495a9ce4cb38a63e9161
- https://git.kernel.org/stable/c/ea5f97dbdcb1651581a22bd10afd2f0dd9dc11d6
- https://git.kernel.org/stable/c/3542c90797bc3ab83ebab54b737d751cf3682036
- https://git.kernel.org/stable/c/f2e467a48287c868818085aa35389a224d226732
ADP enrichment
No English description supplied.
No English description supplied.
No English description supplied.
No references supplied.