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[PATCH] packet driver permission checking fix

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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>
This commit is contained in:
Peter Osterlund 2005-05-20 13:59:06 -07:00 committed by Linus Torvalds
parent 1c7878f024
commit 46f4e1b7d5
1 changed files with 7 additions and 1 deletions
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8
drivers/block/pktcdvd.c
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@ -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;