Bug 2451236 (CVE-2026-23346)

Summary: CVE-2026-23346 kernel: arm64: io: Extract user memory type in ioremap_prot()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in the Linux kernel, specifically within the arm64 architecture's I/O memory mapping (ioremap_prot) functionality. On systems with Privileged Access Never (PAN) enabled, a local user could exploit this by triggering a scenario where the kernel attempts to access a user memory mapping with incorrect permission controls. This leads to the kernel being unable to read from memory, resulting in a system crash and a denial of service.
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Description OSIDB Bzimport 2026-03-25 11:06:16 UTC 
In the Linux kernel, the following vulnerability has been resolved:

arm64: io: Extract user memory type in ioremap_prot()

The only caller of ioremap_prot() outside of the generic ioremap()
implementation is generic_access_phys(), which passes a 'pgprot_t' value
determined from the user mapping of the target 'pfn' being accessed by
the kernel. On arm64, the 'pgprot_t' contains all of the non-address
bits from the pte, including the permission controls, and so we end up
returning a new user mapping from ioremap_prot() which faults when
accessed from the kernel on systems with PAN:

  | Unable to handle kernel read from unreadable memory at virtual address ffff80008ea89000
  | ...
  | Call trace:
  |   __memcpy_fromio+0x80/0xf8
  |   generic_access_phys+0x20c/0x2b8
  |   __access_remote_vm+0x46c/0x5b8
  |   access_remote_vm+0x18/0x30
  |   environ_read+0x238/0x3e8
  |   vfs_read+0xe4/0x2b0
  |   ksys_read+0xcc/0x178
  |   __arm64_sys_read+0x4c/0x68

Extract only the memory type from the user 'pgprot_t' in ioremap_prot()
and assert that we're being passed a user mapping, to protect us against
any changes in future that may require additional handling. To avoid
falsely flagging users of ioremap(), provide our own ioremap() macro
which simply wraps __ioremap_prot().
Comment 1 Alexander B 2026-03-25 14:14:31 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026032535-CVE-2026-23346-faed@gregkh/T