Commit 04518bfe authored by Jeff Garzik's avatar Jeff Garzik Committed by Linus Torvalds
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[PATCH] ISDN: fix drivers, by handling errors thrown by ->readstat()

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: default avatarJeff Garzik <>
Cc: Karsten Keil <>
Cc: <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 078d3965
......@@ -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,
len = dev->drv[drvidx]->interface->readstat(buf, count,
drvidx, isdn_minor2chan(minor));
if (len < 0) {
retval = len;
goto out;
} else {
len = 0;
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