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 <[email protected]>
---
drivers/isdn/i4l/isdn_common.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/isdn/i4l/isdn_common.c b/drivers/isdn/i4l/isdn_common.c
index c3d79ee..69aee26 100644
--- a/drivers/isdn/i4l/isdn_common.c
+++ b/drivers/isdn/i4l/isdn_common.c
@@ -1134,9 +1134,12 @@ isdn_read(struct file *file, char __user
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;
}
-
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