# \[PATCH v1 6/7\] mm: ignore MAP\_DENYWRITE in ksys\_mmap\_pgoff()

- From: David Hildenbrand \<hidden\>
- Date: 2021-08-12 08:46:19 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2021/08/212178
- Thread: https://ratatoskr.run/linux-unionfs/2021/08/212172/t.md

```text
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 <redacted>
---
 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

```