Wind River Support Network

Description

In the Linux kernel, the following vulnerability has been resolved:  arm64: io: Reject non-user protection in ioremap_prot()  Mapping a stack-top page via /dev/mem with PROT_NONE and then reading that process's /proc/<pid>/cmdline triggers a spurious WARN in ioremap_prot() through generic_access_phys():    WARNING: ./arch/arm64/include/asm/io.h:275 at generic_access_phys   Call trace:     generic_access_phys+0x1c8/0x228 (P)     __access_remote_vm+0x2b4/0x398     access_remote_vm+0x14/0x30     get_mm_cmdline+0xf8/0x2a0     proc_pid_cmdline_read+0x68/0x120  generic_access_phys() passes the protection derived from the user PTE to ioremap_prot(). On arm64, a PROT_NONE mapping is represented by a present-invalid PTE, so pte_present() still returns true and the protection reaches ioremap_prot().  A PROT_NONE mapping does not have PTE_USER, causing the existing WARN_ON_ONCE() in ioremap_prot() to fire even though this is a valid user mapping. Execute-only mappings have the same issue and must not be readable through this path either.  ioremap_prot() should therefore reject protection values without PTE_USER without warning. This makes the access fail cleanly for PROT_NONE and execute-only mappings while retaining the existing user-protection contract.