[PATCH] mm/nommu.c: check read permission in validate_mmap_request()

[PATCH] mm/nommu.c: check read permission in validate_mmap_request()

[graff.yang]

From: Graff Yang <graff.yang@gmail.com>

According to the POSIX (1003.1-2008), the file shall have been opened
with read permission, regardless of the protection options specified.
The ltp test cases mmap06/07 need this.

Signed-off-by: Graff Yang <graff.yang@gmail.com>
---
 mm/nommu.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/mm/nommu.c b/mm/nommu.c
index 53cab10..ac13b23 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -922,6 +922,10 @@ 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) &&
-- 
1.6.1

Re: [PATCH] mm/nommu.c: check read permission in validate_mmap_request()

[Paul Mundt]

On Fri, Aug 14, 2009 at 11:19:21AM +0800, graff.yang@gmail.com wrote:
> From: Graff Yang <graff.yang@gmail.com>
> 
> According to the POSIX (1003.1-2008), the file shall have been opened
> with read permission, regardless of the protection options specified.
> The ltp test cases mmap06/07 need this.
> 
> Signed-off-by: Graff Yang <graff.yang@gmail.com>

Looks good. This brings it more in line with MMU Linux anyways, so it's
worthwhile regardless.

Acked-by: Paul Mundt <lethal@linux-sh.org>