{"id":"CVE-2026-90201","published":"2026-09-17T17:17:15.053","lastModified":"2026-09-17T17:17:15.053","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: page_pool: fix UAF in __page_pool_release_netmem_dma on xa_cmpxchg race\n\nThis bug was discovered while testing the hns3 driver under channel\nreconfiguration (`ethtool -L` / `ethtool -G`) with iperf3 traffic on\narm64. The race is intermittently triggered when page_pool_destroy()\nruns page_pool_scrub() concurrently with page return via\npage_pool_put_netmem() on a different CPU. A WARN in\npage_pool_clear_pp_info() surfaced the dangling DMA index bits left\nby the cmpxchg loser, which led to the investigation.\n\npage_pool_scrub() iterates pool->dma_mapped via xa_for_each() with no\npage ref held. __page_pool_release_netmem_dma() currently reads and\nwrites netmem fields (dma_addr, DMA index bits in pp_magic) after\nxa_cmpxchg() returns. The unref path calls put_page() unconditionally\nregardless of the cmpxchg outcome; when it loses the cmpxchg, it still\nfrees the page before the scrub winner finishes these netmem accesses,\nso scrub touches a freed page -- a Use-After-Free.\n\nFix this by splitting the DMA release into two functions:\n\n1. __page_pool_unmap_netmem_dma() caches dma_addr before xa_cmpxchg(),\n   does the cmpxchg to remove the DMA mapping, and calls dma_unmap on\n   the cached address. It never touches netmem fields after the cmpxchg,\n   making it safe for the scrub path which holds no page ref.\n\n2. __page_pool_release_netmem_dma() wraps the above and additionally\n   clears dma_addr and DMA index bits in netmem fields. This is safe\n   only when the caller holds a page ref, so it is used by the return\n   path (page_pool_return_netmem).\n\nThe scrub path calls __page_pool_unmap_netmem_dma() directly; the return\npath calls __page_pool_release_netmem_dma().","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/24ef02f934eeb48830cff6b739abc3c62b1d107b","tags":[]},{"url":"https://git.kernel.org/stable/c/424a9fc4876cc7f28e9cb0aa8d92e920d726e350","tags":[]},{"url":"https://git.kernel.org/stable/c/9b65b0253ad5a66f73efee9a79a21a1e2b57cf59","tags":[]},{"url":"https://git.kernel.org/stable/c/bbfef303f980c1c078b8fa142e10a0e2fbcdd247","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}