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Subject[047/127] firewire: cdev: fix information leak
2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Stefan Richter <stefanr@s5r6.in-berlin.de>

commit 9cac00b8f0079d5d3d54ec4dae453d58dec30e7c upstream.

A userspace client got to see uninitialized stack-allocated memory if it
specified an _IOC_READ type of ioctl and an argument size larger than
expected by firewire-core's ioctl handlers (but not larger than the
core's union ioctl_arg).

Fix this by clearing the requested buffer size to zero, but only at _IOR
ioctls. This way, there is almost no runtime penalty to legitimate
ioctls. The only legitimate _IOR is FW_CDEV_IOC_GET_CYCLE_TIMER with 12
or 16 bytes to memset.

[Another way to fix this would be strict checking of argument size (and
possibly direction) vs. command number. However, we then need a lookup
table, and we need to allow for slight size deviations in case of 32bit
userland on 64bit kernel.]

Reported-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
[ Backported to 2.6.32 firewire core -maks ]
Signed-off-by: maximilian attems <max@stro.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/firewire/core-cdev.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -1299,24 +1299,24 @@ static int dispatch_ioctl(struct client
int ret;

if (_IOC_TYPE(cmd) != '#' ||
- _IOC_NR(cmd) >= ARRAY_SIZE(ioctl_handlers))
+ _IOC_NR(cmd) >= ARRAY_SIZE(ioctl_handlers) ||
+ _IOC_SIZE(cmd) > sizeof(buffer))
return -EINVAL;

- if (_IOC_DIR(cmd) & _IOC_WRITE) {
- if (_IOC_SIZE(cmd) > sizeof(buffer) ||
- copy_from_user(buffer, arg, _IOC_SIZE(cmd)))
+ if (_IOC_DIR(cmd) == _IOC_READ)
+ memset(&buffer, 0, _IOC_SIZE(cmd));
+
+ if (_IOC_DIR(cmd) & _IOC_WRITE)
+ if (copy_from_user(buffer, arg, _IOC_SIZE(cmd)))
return -EFAULT;
- }

ret = ioctl_handlers[_IOC_NR(cmd)](client, buffer);
if (ret < 0)
return ret;

- if (_IOC_DIR(cmd) & _IOC_READ) {
- if (_IOC_SIZE(cmd) > sizeof(buffer) ||
- copy_to_user(arg, buffer, _IOC_SIZE(cmd)))
+ if (_IOC_DIR(cmd) & _IOC_READ)
+ if (copy_to_user(arg, buffer, _IOC_SIZE(cmd)))
return -EFAULT;
- }

return ret;
}



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