diff options
| author | Catalin Marinas <catalin.marinas@arm.com> | 2026-02-23 17:45:31 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-03-19 16:15:14 +0100 |
| commit | 154eb7c43f4b6b00d32a08c04bc1c3cc3b8e1c11 (patch) | |
| tree | 1890781226252f5cca150b218ad0bc528107d4cd /arch | |
| parent | 5784d1fb75308d1cf00eb7124883d2e8546430da (diff) | |
arm64: gcs: Honour mprotect(PROT_NONE) on shadow stack mappings
commit 47a8aad135ac1aed04b7b0c0a8157fd208075827 upstream.
vm_get_page_prot() short-circuits the protection_map[] lookup for a
VM_SHADOW_STACK mapping since it uses a different PIE index from the
typical read/write/exec permissions. However, the side effect is that it
also ignores mprotect(PROT_NONE) by creating an accessible PTE.
Special-case the !(vm_flags & VM_ACCESS_FLAGS) flags to use the
protection_map[VM_NONE] permissions instead. No GCS attributes are
required for an inaccessible PTE.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Fixes: 6497b66ba694 ("arm64/mm: Map pages for guarded control stack")
Cc: stable@vger.kernel.org
Cc: Mark Brown <broonie@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm64/mm/mmap.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c index 75f343009b4b..92b2f5097a96 100644 --- a/arch/arm64/mm/mmap.c +++ b/arch/arm64/mm/mmap.c @@ -91,7 +91,11 @@ pgprot_t vm_get_page_prot(vm_flags_t vm_flags) /* Short circuit GCS to avoid bloating the table. */ if (system_supports_gcs() && (vm_flags & VM_SHADOW_STACK)) { - prot = gcs_page_prot; + /* Honour mprotect(PROT_NONE) on shadow stack mappings */ + if (vm_flags & VM_ACCESS_FLAGS) + prot = gcs_page_prot; + else + prot = pgprot_val(protection_map[VM_NONE]); } else { prot = pgprot_val(protection_map[vm_flags & (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]); |