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().
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().
Published:
2026-09-17
Score:
n/a
EPSS:
n/a
KEV:
No
Impact:
n/a
Action:
n/a
Analysis
No analysis available yet.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
||||||||||||||||||||||||
| Linux | Linux | affected |
|
No data.
No data.
No data available yet.
Remediation
No remediation available yet.
Tracking
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Advisories
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References
History
Thu, 17 Sep 2026 16:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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(). | |
| Title | net: page_pool: fix UAF in __page_pool_release_netmem_dma on xa_cmpxchg race | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-17T16:07:18.838Z
Reserved: 2026-09-11T19:38:34.792Z
Link: CVE-2026-90201
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-17T17:17:15.053
Modified: 2026-09-17T17:17:15.053
Link: CVE-2026-90201
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.