Bug 2484449 (CVE-2026-46268)

Summary: CVE-2026-46268 kernel: PCI/P2PDMA: Fix p2pmem_alloc_mmap() warning condition
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's PCI/P2PDMA subsystem. Specifically, a warning condition in the `p2pmem_alloc_mmap()` function can be triggered due to an incorrect page reference count assertion. This issue occurs when the `CONFIG_DEBUG_VM` option is enabled, leading to kernel warning messages. While primarily a debugging concern, it may indicate unexpected system behavior or instability under specific configurations.
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Description OSIDB Bzimport 2026-06-03 18:01:59 UTC 
In the Linux kernel, the following vulnerability has been resolved:

PCI/P2PDMA: Fix p2pmem_alloc_mmap() warning condition

Commit b7e282378773 has already changed the initial page refcount of
p2pdma page from one to zero, however, in p2pmem_alloc_mmap() it uses
"VM_WARN_ON_ONCE_PAGE(!page_ref_count(page))" to assert the initial page
refcount should not be zero and the following will be reported when
CONFIG_DEBUG_VM is enabled:

  page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x380400000
  flags: 0x20000000002000(reserved|node=0|zone=4)
  raw: 0020000000002000 ff1100015e3ab440 0000000000000000 0000000000000000
  raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
  page dumped because: VM_WARN_ON_ONCE_PAGE(!page_ref_count(page))
  ------------[ cut here ]------------
  WARNING: CPU: 5 PID: 449 at drivers/pci/p2pdma.c:240 p2pmem_alloc_mmap+0x83a/0xa60

Fix by using "page_ref_count(page)" as the assertion condition.
Comment 1 Keith Grant 2026-06-03 19:57:23 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026060338-CVE-2026-46268-1753@gregkh/T