xsk: fix refcount underflow in error path

Summary

In the Linux kernel, the following vulnerability has been resolved: xsk: fix refcount underflow in error path Fix a refcount underflow problem reported by syzbot that can happen when a system is running out of memory. If xp_alloc_tx_descs() fails, and it can only fail due to not having enough memory, then the error path is triggered. In this error path, the refcount of the pool is decremented as it has incremented before. However, the reference to the pool in the socket was not nulled. This means that when the socket is closed later, the socket teardown logic will think that there is a pool attached to the socket and try to decrease the refcount again, leading to a refcount underflow. I chose this fix as it involved adding just a single line. Another option would have been to move xp_get_pool() and the assignment of xs->pool to after the if-statement and using xs_umem->pool instead of xs->pool in the whole if-statement resulting in somewhat simpler code, but this would have led to much more churn in the code base perhaps making it harder to backport.

Timeline

1. Oct 22, 2025, 1:23 PM UTCCVE published
2. Oct 15, 2026, 9:36 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Oct 15, 2026, 9:41 PM UTCRecord last updated

Affected versions

• Linux Linux

  From f7019562f142bc041f9cde63af338d1886585923 · fixed in 789fcd94c9cac133dd4d96e193188661aca9f6c3; From ba3beec2ec1d3b4fd8672ca6e781dac4b3267f6e · fixed in 15b453cf7348973217558235b9ece2ee5fea6777; From ba3beec2ec1d3b4fd8672ca6e781dac4b3267f6e · fixed in 3e7722c31d4167eb7f3ffd35aba52cab69b79072; From ba3beec2ec1d3b4fd8672ca6e781dac4b3267f6e · fixed in 85c2c79a07302fe68a1ad5cc449458cc559e314d; From 5.15.47 · fixed in 5.15.127; From 5.17.15 · fixed in 5.18

• Linux Linux

  5.18

• KernelLinux

  fixed in 5.15.127; From 5.16.0 · fixed in 6.1.46; From 5.18.0 · fixed in 6.4.11

References 4