CVE-2026-90201

Summary

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().

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/bbfef303f980c1c078b8fa142e10a0e2fbcdd247
• https://git.kernel.org/stable/c/424a9fc4876cc7f28e9cb0aa8d92e920d726e350
• https://git.kernel.org/stable/c/9b65b0253ad5a66f73efee9a79a21a1e2b57cf59
• https://git.kernel.org/stable/c/24ef02f934eeb48830cff6b739abc3c62b1d107b

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