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cifs: don't dereference smb_file_target before null check

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[ Upstream commit 8c6c9bed8773375b1d54ccca2911ec892c59db5d ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Colin Ian King 2018-11-01 13:14:30 +00:00 committed by Greg Kroah-Hartman
parent e186413178
commit f89c9ff374
1 changed files with 5 additions and 2 deletions
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7
fs/cifs/cifsfs.c
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@ -927,8 +927,8 @@ static int cifs_clone_file_range(struct file *src_file, loff_t off,
struct inode *src_inode = file_inode(src_file);
struct inode *target_inode = file_inode(dst_file);
struct cifsFileInfo *smb_file_src = src_file->private_data;
struct cifsFileInfo *smb_file_target = dst_file->private_data;
struct cifs_tcon *target_tcon = tlink_tcon(smb_file_target->tlink);
struct cifsFileInfo *smb_file_target;
struct cifs_tcon *target_tcon;
unsigned int xid;
int rc;
@ -942,6 +942,9 @@ static int cifs_clone_file_range(struct file *src_file, loff_t off,
goto out;
}
smb_file_target = dst_file->private_data;
target_tcon = tlink_tcon(smb_file_target->tlink);
/*
* Note: cifs case is easier than btrfs since server responsible for
* checks for proper open modes and file type and if it wants