cifs: don't dereference smb_file_target before null check
authorColin Ian King <colin.king@canonical.com>
Thu, 1 Nov 2018 13:14:30 +0000 (13:14 +0000)
committerSteve French <stfrench@microsoft.com>
Fri, 2 Nov 2018 19:09:42 +0000 (14:09 -0500)
commit8c6c9bed8773375b1d54ccca2911ec892c59db5d
treec45857d15024dc656dc7a20fb0e75ec46b2f85b8
parentbe4eb68846dc4450a9a4998d7c16d9f4955f9988
cifs: don't dereference smb_file_target before null check

There is a null check on dst_file->private data which suggests
it can be potentially null. However, before this check, pointer
smb_file_target is derived from dst_file->private and dereferenced
in the call to tlink_tcon, hence there is a potential null pointer
deference.

Fix this by assigning smb_file_target and target_tcon after the
null pointer sanity checks.

Detected by CoverityScan, CID#1475302 ("Dereference before null check")

Fixes: 04b38d601239 ("vfs: pull btrfs clone API to vfs layer")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
fs/cifs/cifsfs.c