From 556ac52bb1e76cc28fd30aa117b42989965b3efd Mon Sep 17 00:00:00 2001 From: Pali Rohár Date: Sat, 28 Sep 2024 23:59:47 +0200 Subject: cifs: Validate content of NFS reparse point buffer MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Symlink target location stored in DataBuffer is encoded in UTF-16. So check that symlink DataBuffer length is non-zero and even number. And check that DataBuffer does not contain UTF-16 null codepoint because Linux cannot process symlink with null byte. DataBuffer for char and block devices is 8 bytes long as it contains two 32-bit numbers (major and minor). Add check for this. DataBuffer buffer for sockets and fifos zero-length. Add checks for this. Signed-off-by: Pali Rohár Reviewed-by: Paulo Alcantara (Red Hat) Signed-off-by: Steve French --- fs/smb/client/reparse.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c index 8ea7a848aa39..f0cfcf32de19 100644 --- a/fs/smb/client/reparse.c +++ b/fs/smb/client/reparse.c @@ -330,6 +330,18 @@ static int parse_reparse_posix(struct reparse_posix_data *buf, switch ((type = le64_to_cpu(buf->InodeType))) { case NFS_SPECFILE_LNK: + if (len == 0 || (len % 2)) { + cifs_dbg(VFS, "srv returned malformed nfs symlink buffer\n"); + return -EIO; + } + /* + * Check that buffer does not contain UTF-16 null codepoint + * because Linux cannot process symlink with null byte. + */ + if (UniStrnlen((wchar_t *)buf->DataBuffer, len/2) != len/2) { + cifs_dbg(VFS, "srv returned null byte in nfs symlink target location\n"); + return -EIO; + } data->symlink_target = cifs_strndup_from_utf16(buf->DataBuffer, len, true, cifs_sb->local_nls); @@ -341,8 +353,19 @@ static int parse_reparse_posix(struct reparse_posix_data *buf, break; case NFS_SPECFILE_CHR: case NFS_SPECFILE_BLK: + /* DataBuffer for block and char devices contains two 32-bit numbers */ + if (len != 8) { + cifs_dbg(VFS, "srv returned malformed nfs buffer for type: 0x%llx\n", type); + return -EIO; + } + break; case NFS_SPECFILE_FIFO: case NFS_SPECFILE_SOCK: + /* DataBuffer for fifos and sockets is empty */ + if (len != 0) { + cifs_dbg(VFS, "srv returned malformed nfs buffer for type: 0x%llx\n", type); + return -EIO; + } break; default: cifs_dbg(VFS, "%s: unhandled inode type: 0x%llx\n", -- cgit v1.2.3