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
pointe...

Classification

CVE ID: CVE-2024-26924

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.04% (probability of being exploited)

EPSS Percentile: 12.41% (scored less or equal to compared to others)

EPSS Date: 2025-02-04 (when was this score calculated)

References

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/ebf7c9746f073035ee26209e38c3a1170f7b349a
https://git.kernel.org/stable/c/14b001ba221136c15f894577253e8db535b99487
https://git.kernel.org/stable/c/3cfc9ec039af60dbd8965ae085b2c2ccdcfbe1cc

Timeline