[PATCH v1 6/7] mm: ignore MAP_DENYWRITE in ksys_mmap_pgoff()

David Hildenbrand
2021-08-12T08:46:22Z

Let's also remove masking off MAP_DENYWROTE from ksys_mmap_pgoff():
the last in-tree occurrence of MAP_DENYWRITE is now in LEGACY_MAP_MASK,
which accepts the flag e.g., for MAP_SHARED_VALIDATE; however, the flag
is ignored throughout the kernel now.

Add a comment to LEGACY_MAP_MASK stating that MAP_DENYWRITE is ignored.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
include/linux/mman.h | 3 ++-
mm/mmap.c | 2 --
mm/nommu.c | 2 --
3 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/include/linux/mman.h b/include/linux/mman.h
index bd9aadda047b..b66e91b8176c 100644
--- a/include/linux/mman.h
+++ b/include/linux/mman.h
@@ -32,7 +32,8 @@
* The historical set of flags that all mmap implementations implicitly
* support when a ->mmap_validate() op is not provided in file_operations.
*
- * MAP_EXECUTABLE is completely ignored throughout the kernel.
+ * MAP_EXECUTABLE and MAP_DENYWRITE are completely ignored throughout the
+ * kernel.
*/
#define LEGACY_MAP_MASK (MAP_SHARED \
| MAP_PRIVATE \
diff --git a/mm/mmap.c b/mm/mmap.c
index 589dc1dc13db..bf11fc6e8311 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1626,8 +1626,6 @@ unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
return PTR_ERR(file);
}

- flags &= ~MAP_DENYWRITE;
-
retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
out_fput:
if (file)
diff --git a/mm/nommu.c b/mm/nommu.c
index 3a93d4054810..0987d131bdfc 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1296,8 +1296,6 @@ unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
goto out;
}

- flags &= ~MAP_DENYWRITE;
-
retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);

if (file)
--
2.31.1