From 46f4e1b7d5fa3ddf2486bf69716c404147e38ebf Mon Sep 17 00:00:00 2001
From: Peter Osterlund <petero2@telia.com>
Date: Fri, 20 May 2005 13:59:06 -0700
Subject: [PATCH] packet driver permission checking fix
If you tried to open a packet device first in read-only mode and then a
second time in read-write mode, the second open succeeded even though the
device was not correctly set up for writing. If you then tried to write
data to the device, the writes would fail with I/O errors.
This patch prevents that problem by making the second open fail with
-EBUSY.
Signed-off-by: Peter Osterlund <petero2@telia.com>
Cc: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
drivers/block/pktcdvd.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
(limited to 'drivers')
diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index b9a6b7ad64..bc56770bcc 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -2021,7 +2021,13 @@ static int pkt_open(struct inode *inode, struct file *file)
BUG_ON(pd->refcnt < 0);
pd->refcnt++;
- if (pd->refcnt == 1) {
+ if (pd->refcnt > 1) {
+ if ((file->f_mode & FMODE_WRITE) &&
+ !test_bit(PACKET_WRITABLE, &pd->flags)) {
+ ret = -EBUSY;
+ goto out_dec;
+ }
+ } else {
if (pkt_open_dev(pd, file->f_mode & FMODE_WRITE)) {
ret = -EIO;
goto out_dec;
--
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