cifs: Validate content of NFS reparse point buffer
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 <pali@kernel.org> Reviewed-by: Paulo Alcantara (Red Hat) <pc@manguebit.com> Signed-off-by: Steve French <stfrench@microsoft.com>
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@ -330,6 +330,18 @@ static int parse_reparse_posix(struct reparse_posix_data *buf,
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switch ((type = le64_to_cpu(buf->InodeType))) {
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case NFS_SPECFILE_LNK:
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if (len == 0 || (len % 2)) {
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cifs_dbg(VFS, "srv returned malformed nfs symlink buffer\n");
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return -EIO;
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}
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/*
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* Check that buffer does not contain UTF-16 null codepoint
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* because Linux cannot process symlink with null byte.
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*/
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if (UniStrnlen((wchar_t *)buf->DataBuffer, len/2) != len/2) {
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cifs_dbg(VFS, "srv returned null byte in nfs symlink target location\n");
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return -EIO;
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}
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data->symlink_target = cifs_strndup_from_utf16(buf->DataBuffer,
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len, true,
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cifs_sb->local_nls);
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@ -341,8 +353,19 @@ static int parse_reparse_posix(struct reparse_posix_data *buf,
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break;
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case NFS_SPECFILE_CHR:
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case NFS_SPECFILE_BLK:
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/* DataBuffer for block and char devices contains two 32-bit numbers */
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if (len != 8) {
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cifs_dbg(VFS, "srv returned malformed nfs buffer for type: 0x%llx\n", type);
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return -EIO;
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}
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break;
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case NFS_SPECFILE_FIFO:
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case NFS_SPECFILE_SOCK:
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/* DataBuffer for fifos and sockets is empty */
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if (len != 0) {
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cifs_dbg(VFS, "srv returned malformed nfs buffer for type: 0x%llx\n", type);
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return -EIO;
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}
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break;
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default:
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cifs_dbg(VFS, "%s: unhandled inode type: 0x%llx\n",
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