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[PATCH] ISDN: fix drivers, by handling errors thrown by ->readstat()

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This is a particularly ugly on-failure bug, possibly security, since the
lack of error handling here is covering up another class of bug: failure to
handle copy_to_user() return values.

The I4L API function ->readstat() returns an integer, and by looking at
several existing driver implementations, it is clear that a negative return
value was meant to indicate an error.

Given that several drivers already return a negative value indicating an
errno-style error, the current code would blindly accept that [negative]
value as a valid amount of bytes read.  Obvious damage ensues.

Correcting ->readstat() handling to properly notice errors fixes the
existing code to work correctly on error, and enables future patches to
more easily indicate errors during operation.

Signed-off-by: Jeff Garzik <jeff@garzik.org>
Cc: Karsten Keil <kkeil@suse.de>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Jeff Garzik 2006-10-17 00:10:39 -07:00 committed by Linus Torvalds
parent 078d396598
commit 04518bfe8e
1 changed files with 6 additions and 3 deletions
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9
drivers/isdn/i4l/isdn_common.c
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@ -1134,9 +1134,12 @@ isdn_read(struct file *file, char __user *buf, size_t count, loff_t * off)
if (dev->drv[drvidx]->interface->readstat) {
if (count > dev->drv[drvidx]->stavail)
count = dev->drv[drvidx]->stavail;
len = dev->drv[drvidx]->interface->
readstat(buf, count, drvidx,
isdn_minor2chan(minor));
len = dev->drv[drvidx]->interface->readstat(buf, count,
drvidx, isdn_minor2chan(minor));
if (len < 0) {
retval = len;
goto out;
}
} else {
len = 0;
}