From 8c6c9bed8773375b1d54ccca2911ec892c59db5d Mon Sep 17 00:00:00 2001
From: Colin Ian King <colin.king@canonical.com>
Date: Thu, 1 Nov 2018 13:14:30 +0000
Subject: [PATCH] cifs: don't dereference smb_file_target before null check
Git-commit: 8c6c9bed8773375b1d54ccca2911ec892c59db5d
Patch-mainline: v4.20-rc1
References: bsc#1051510, bsc#1144333
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>
Acked-by: Paulo Alcantara <palcantara@suse.de>
---
fs/cifs/cifsfs.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 1b21262ec874..865706edb307 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -999,8 +999,8 @@ static loff_t cifs_remap_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;
@@ -1017,6 +1017,9 @@ static loff_t cifs_remap_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
--
2.16.4