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cifs: fix out-of-bound memory access when calling smb3_notify() at mount point

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commit a637f4ae03 upstream.

If smb3_notify() is called at mount point of CIFS, build_path_from_dentry()
returns the pointer to kmalloc-ed memory with terminating zero (this is
empty FileName to be passed to SMB2 CREATE request). This pointer is assigned
to the `path` variable.
Then `path + 1` (to skip first backslash symbol) is passed to
cifs_convert_path_to_utf16(). This is incorrect for empty path and causes
out-of-bound memory access.

Get rid of this "increase by one". cifs_convert_path_to_utf16() already
contains the check for leading backslash in the path.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=212693
CC: <stable@vger.kernel.org> # v5.6+
Signed-off-by: Eugene Korenevsky <ekorenevsky@astralinux.ru>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eugene Korenevsky 2021-04-16 10:35:30 +03:00 • committed by Greg Kroah-Hartman
commit 23d7b4a8f7
1 changed files with 1 additions and 1 deletions
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2
fs/cifs/smb2ops.c
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@ -2174,7 +2174,7 @@ smb3_notify(const unsigned int xid, struct file *pfile,
cifs_sb = CIFS_SB(inode->i_sb);
utf16_path = cifs_convert_path_to_utf16(path + 1, cifs_sb);
utf16_path = cifs_convert_path_to_utf16(path, cifs_sb);
if (utf16_path == NULL) {
rc = -ENOMEM;
goto notify_exit;