CVE-2026-90201 net: page_pool: fix UAF in __page_pool_release_netmem_dma on xa_cmpxchg race
A race condition in the Linux kernel page pool allows a use-after-free, potentially leading to code execution or system crash.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-90201?
CVE-2026-90201 is an use after free vulnerability in Linux, published on 17 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net: page_pool: fix UAF in __page_pool_release_netmem_dma on xa_cmpxchg race
This bug was discovered while testing the hns3 driver under channel reconfiguration (`ethtool -L` / `ethtool -G`) with iperf3 traffic on arm64. The race is intermittently triggered when page_pool_destroy() runs page_pool_scrub() concurrently with page return via page_pool_put_netmem() on a different CPU. A WARN in page_pool_clear_pp_info() surfaced the dangling DMA index bits left by the cmpxchg loser, which led to the investigation.
page_pool_scrub() iterates pool->dma_mapped via xa_for_each() with no page ref held. __page_pool_release_netmem_dma() currently reads and writes netmem fields (dma_addr, DMA index bits in pp_magic) after xa_cmpxchg() returns. The unref path calls put_page() unconditionally regardless of the cmpxchg outcome; when it loses the cmpxchg, it still frees the page before the scrub winner finishes these netmem accesses, so scrub touches a freed page -- a Use-After-Free.
Fix this by splitting the DMA release into two functions:
1. __page_pool_unmap_netmem_dma() caches dma_addr before xa_cmpxchg(), does the cmpxchg to remove the DMA mapping, and calls dma_unmap on the cached address. It never touches netmem fields after the cmpxchg, making it safe for the scrub path which holds no page ref.
2. __page_pool_release_netmem_dma() wraps the above and additionally clears dma_addr and DMA index bits in netmem fields. This is safe only when the caller holds a page ref, so it is used by the return path (page_pool_return_netmem).
The scrub path calls __page_pool_unmap_netmem_dma() directly; the return path calls __page_pool_release_netmem_dma().
Which versions are affected by CVE-2026-90201?
How do I fix CVE-2026-90201?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-90201 being exploited?
There is no known exploitation of CVE-2026-90201 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-90201, DEBIAN-CVE-2026-90201, GHSA-6rvq-r5r4-hcv8, UBUNTU-CVE-2026-90201.