btrfs-progs: Avoid reading bad fd in case of missing device.

Offline btrfs tools, like btrfs-image, will infinitely loop when there
is missing device.

The reason is, for missing device, it's fd will be set to -1, but before
we reading, we only check the fd validation by checking if it's 0.
So in that case, -1 will pass the validation check, and cause pread to
return 0, and loop to read.

Just change the validation check from "== 0" to "<= 0" to avoid such
problem.

Reported-by: Timothy Normand Miller <theosib@gmail.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

0 files changed, 0 insertions, 0 deletions