linux-kernel - [PATCH] NOMMU: Check fd read permission in validate_mmap

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Message-ID: <20090814112932.16091.15120.stgit@warthog.procyon.org.uk>
Date:	Fri, 14 Aug 2009 12:29:32 +0100
From:	David Howells <dhowells@...hat.com>
To:	torvalds@...l.org, akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org,
	uclinux-dist-devel@...ckfin.uclinux.org,
	Graff Yang <graff.yang@...il.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	David Howells <dhowells@...hat.com>
Subject: [PATCH] NOMMU: Check fd read permission in validate_mmap_request()

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

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@...il.com>
Acked-by: Paul Mundt <lethal@...ux-sh.org>
Signed-off-by: David Howells <dhowells@...hat.com>
---

 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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