UBUNTU-CVE-2025-40199
In the Linux kernel, the following vulnerability has been resolved: page_pool: Fix PP_MAGIC_MASK to avoid crashing on some 32-bit arches Helge reported that the introduction of PP_MAGIC_MASK let to crashes on boot on his 32-bit parisc machine. The cause of this is the mask is set too wide, so the page_pool_page_is_pp() incurs false positives which crashes the machine. Just disabling the check in page_pool_is_pp() will lead to the page_pool code itself malfunctioning; so instead of doing this, this patch changes the define for PP_DMA_INDEX_BITS to avoid mistaking arbitrary kernel pointers for page_pool-tagged pages. The fix relies on the kernel pointers that alias with the pp_magic field always being above PAGE_OFFSET. With this assumption, we can use the lowest bit of the value of PAGE_OFFSET as the upper bound of the PP_DMA_INDEX_MASK, which should avoid the false positives. Because we cannot rely on PAGE_OFFSET always being a compile-time constant, nor on it always being >0, we fall back to disabling the dma_index storage when there are not enough bits available. This leaves us in the situation we were in before the patch in the Fixes tag, but only on a subset of architecture configurations. This seems to be the best we can do until the transition to page types in complete for page_pool pages. v2: - Make sure there's at least 8 bits available and that the PAGE_OFFSET bit calculation doesn't wrap
02 / AFFECTED SOFTWARE
Affected packages
11 explicit affected versions
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51 explicit affected versions
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8 explicit affected versions
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13 explicit affected versions
7 explicit affected versions
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16 explicit affected versions
3 explicit affected versions
13 explicit affected versions
26 explicit affected versions
45 explicit affected versions
37 explicit affected versions
14 explicit affected versions
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9 explicit affected versions
9 explicit affected versions
11 explicit affected versions
6 explicit affected versions
7 explicit affected versions
4 explicit affected versions
1 explicit affected versions
13 explicit affected versions
43 explicit affected versions
6 explicit affected versions
10 explicit affected versions
8 explicit affected versions
14 explicit affected versions
4 explicit affected versions
78 explicit affected versions
6 explicit affected versions
11 explicit affected versions
1 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: page_pool: Fix PP_MAGIC_MASK to avoid crashing on some 32-bit arches Helge reported that the introduction of PP_MAGIC_MASK let to crashes on boot on his 32-bit parisc machine. The cause of this is the mask is set too wide, so the page_pool_page_is_pp() incurs false positives which crashes the machine. Just disabling the check in page_pool_is_pp() will lead to the page_pool code itself malfunctioning; so instead of doing this, this patch changes the define for PP_DMA_INDEX_BITS to avoid mistaking arbitrary kernel pointers for page_pool-tagged pages. The fix relies on the kernel pointers that alias with the pp_magic field always being above PAGE_OFFSET. With this assumption, we can use the lowest bit of the value of PAGE_OFFSET as the upper bound of the PP_DMA_INDEX_MASK, which should avoid the false positives. Because we cannot rely on PAGE_OFFSET always being a compile-time constant, nor on it always being >0, we fall back to disabling the dma_index storage when there are not enough bits available. This leaves us in the situation we were in before the patch in the Fixes tag, but only on a subset of architecture configurations. This seems to be the best we can do until the transition to page types in complete for page_pool pages. v2: - Make sure there's at least 8 bits available and that the PAGE_OFFSET bit calculation doesn't wrap
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/95920c2ed02bde551ab654e9749c2ca7bc3100e0
- https://git.kernel.org/stable/c/15b8a5b4cdc16e9a8bb2a548e12a0fd92997605a
- https://git.kernel.org/stable/c/95920c2ed02bde551ab654e9749c2ca7bc3100e0
- https://git.kernel.org/stable/c/f62934cea32c8f7b11b747975d69bf5afe4264cf
- https://ubuntu.com/security/CVE-2025-40199
- https://ubuntu.com/security/notices/USN-8029-1
- https://ubuntu.com/security/notices/USN-8029-2
- https://ubuntu.com/security/notices/USN-8029-3
- https://ubuntu.com/security/notices/USN-8030-1
- https://ubuntu.com/security/notices/USN-8048-1
- https://www.cve.org/CVERecord?id=CVE-2025-40199