nommu: check fd read permission in validate_mmap_request()

According to the POSIX (1003.1-2008), the file descriptor shall have been opened with read permission, regardless of the protection options specified to mmap(). The ltp test cases mmap06/07 need this. Signed-off-by: Graff Yang <[email protected]> Acked-by: Paul Mundt <[email protected]> Signed-off-by: David Howells <[email protected]> Acked-by: Greg Ungerer <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
iegor · Aug 18, 2009 · 28d7a6a · 28d7a6a
1 parent 1915297
commit 28d7a6a
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/mm/nommu.c b/mm/nommu.c
@@ -919,6 +919,10 @@ static int validate_mmap_request(struct file *file,
 		if (!file->f_op->read)
 			capabilities &= ~BDI_CAP_MAP_COPY;
 
+		/* The file shall have been opened with read permission. */
+		if (!(file->f_mode & FMODE_READ))
+			return -EACCES;
+
 		if (flags & MAP_SHARED) {
 			/* do checks for writing, appending and locking */
 			if ((prot & PROT_WRITE) &&