[PATCH] NOMMU: Check fd read permission in validate_mmap_request()

[David Howells]

From: Graff Yang <graff.yang@xxxxxxxxx>

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 <graff.yang@xxxxxxxxx>
Acked-by: Paul Mundt <lethal@xxxxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---

 mm/nommu.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)


diff --git a/mm/nommu.c b/mm/nommu.c
index 1b2b59b..fd1e2b5 100644
--- 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) &&

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