CVE-2024-26924

medium

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_set_pipapo: do not free live element Pablo reports a crash with large batches of elements with a back-to-back add/remove pattern. Quoting Pablo: add_elem("00000000") timeout 100 ms ... add_elem("0000000X") timeout 100 ms del_elem("0000000X") <---------------- delete one that was just added ... add_elem("00005000") timeout 100 ms 1) nft_pipapo_remove() removes element 0000000X Then, KASAN shows a splat. Looking at the remove function there is a chance that we will drop a rule that maps to a non-deactivated element. Removal happens in two steps, first we do a lookup for key k and return the to-be-removed element and mark it as inactive in the next generation. Then, in a second step, the element gets removed from the set/map. The _remove function does not work correctly if we have more than one element that share the same key. This can happen if we insert an element into a set when the set already holds an element with same key, but the element mapping to the existing key has timed out or is not active in the next generation. In such case its possible that removal will unmap the wrong element. If this happens, we will leak the non-deactivated element, it becomes unreachable. The element that got deactivated (and will be freed later) will remain reachable in the set data structure, this can result in a crash when such an element is retrieved during lookup (stale pointer). Add a check that the fully matching key does in fact map to the element that we have marked as inactive in the deactivation step. If not, we need to continue searching. Add a bug/warn trap at the end of the function as well, the remove function must not ever be called with an invisible/unreachable/non-existent element. v2: avoid uneeded temporary variable (Stefano)

References

https://cloud.google.com/support/bulletins/index#gcp-2024-038

https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html

https://git.kernel.org/stable/c/ebf7c9746f073035ee26209e38c3a1170f7b349a

https://git.kernel.org/stable/c/e3b887a9c11caf8357a821260e095f2a694a34f2

https://git.kernel.org/stable/c/7a1679e2d9bfa3b5f8755c2c7113e54b7d42bd46

https://git.kernel.org/stable/c/41d8fdf3afaff312e17466e4ab732937738d5644

https://git.kernel.org/stable/c/3cfc9ec039af60dbd8965ae085b2c2ccdcfbe1cc

https://git.kernel.org/stable/c/14b001ba221136c15f894577253e8db535b99487

Details

Source: Mitre, NVD

Published: 2024-04-25

Updated: 2024-07-03

Risk Information

CVSS v2

Base Score: 6.9

Vector: CVSS2#AV:L/AC:M/Au:N/C:C/I:C/A:C

Severity: Medium

CVSS v3

Base Score: 5.9

Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Severity: Medium