[PATCH v2 06/14] smb: common: compress: drop 'allow_chained' arg from smb_decompress_chained()

That arg is redundant as the function is already only called when
chaining was detected on header.

Also 'NONE' payloads are allowed as the first payload when chained, so
check for it only if not chained.

Other changes:
- remove 'first' variable, check only the first
  payload->Flags == CHAINED, then == NONE in the loop
- code style changes

Signed-off-by: Enzo Matsumiya <[email protected]>
---
 fs/smb/common/compress/compress.c | 72 ++++++++++++++++++-------------
 1 file changed, 41 insertions(+), 31 deletions(-)

diff --git a/fs/smb/common/compress/compress.c b/fs/smb/common/compress/compress.c
index 75d21622c268..64c33af95877 100644
--- a/fs/smb/common/compress/compress.c
+++ b/fs/smb/common/compress/compress.c
@@ -87,8 +87,7 @@ static int smb_decompress_lz77_payload(const u8 **src, u32 *slen, u8 **dst,
 	return 0;
 }
 
-static int smb_decompress_chained(__le16 alg, bool allow_chained,
-				  const struct smb2_compression_hdr *hdr,
+static int smb_decompress_chained(__le16 alg, const struct smb2_compression_hdr *hdr,
 				  u32 slen, void *dst, u32 dlen)
 {
 	const struct smb2_compression_payload_hdr *payload;
@@ -97,10 +96,17 @@ static int smb_decompress_chained(__le16 alg, bool allow_chained,
 	u32 remaining = slen - SMB2_COMPRESSION_CHAINED_HDR_LEN;
 	u8 *out = dst;
 	u32 out_remaining = dlen;
-	bool first = true;
 	int rc;
 
-	if (!allow_chained || orig_size != dlen)
+	if (orig_size != dlen)
+		return -EINVAL;
+
+	payload = (const struct smb2_compression_payload_hdr *)src;
+	/*
+	 * CHAINED marks only the first payload. Requiring NONE on every
+	 * later payload rejects ambiguous or independently chained data.
+	 */
+	if (unlikely(payload->Flags != cpu_to_le16(SMB2_COMPRESSION_FLAG_CHAINED)))
 		return -EINVAL;
 
 	/*
@@ -110,43 +116,40 @@ static int smb_decompress_chained(__le16 alg, bool allow_chained,
 	 */
 	while (remaining) {
 		__le16 payload_alg;
-		__le16 flags;
 		u32 len;
 
 		if (remaining < SMB2_COMPRESSION_PAYLOAD_BASE_LEN)
 			return -EINVAL;
 
-		payload = (const struct smb2_compression_payload_hdr *)src;
 		payload_alg = payload->CompressionAlgorithm;
-		flags = payload->Flags;
-		len = le32_to_cpu(payload->Length);
-
-		/*
-		 * CHAINED marks only the first payload. Requiring NONE on every
-		 * later payload rejects ambiguous or independently chained data.
-		 */
-		if ((first && flags != cpu_to_le16(SMB2_COMPRESSION_FLAG_CHAINED)) ||
-		    (!first && flags != cpu_to_le16(SMB2_COMPRESSION_FLAG_NONE)))
+		if (unlikely(!smb_compress_alg_valid(payload_alg, true)))
 			return -EINVAL;
 
+		len = le32_to_cpu(payload->Length);
 		src += SMB2_COMPRESSION_PAYLOAD_BASE_LEN;
 		remaining -= SMB2_COMPRESSION_PAYLOAD_BASE_LEN;
 
-		if (payload_alg == SMB3_COMPRESS_NONE) {
-			rc = smb_decompress_none(&src, &remaining, &out,
-						 &out_remaining, len);
-		} else if (payload_alg == SMB3_COMPRESS_PATTERN) {
-			rc = smb_decompress_pattern(&src, &remaining, &out,
-						    &out_remaining, len);
-		} else if (payload_alg == alg && alg == SMB3_COMPRESS_LZ77) {
+		rc = -EINVAL;
+		switch (payload_alg) {
+		case SMB3_COMPRESS_NONE:
+			rc = smb_decompress_none(&src, &remaining, &out, &out_remaining, len);
+			break;
+		case SMB3_COMPRESS_LZ77:
 			rc = smb_decompress_lz77_payload(&src, &remaining, &out,
 							 &out_remaining, len);
-		} else {
-			return -EINVAL;
+			break;
+		case SMB3_COMPRESS_PATTERN:
+			rc = smb_decompress_pattern(&src, &remaining, &out, &out_remaining, len);
+			break;
 		}
+
 		if (rc)
 			return rc;
-		first = false;
+
+		payload = (const struct smb2_compression_payload_hdr *)src;
+		if (remaining >= SMB2_COMPRESSION_PAYLOAD_BASE_LEN &&
+		    unlikely(payload->Flags != cpu_to_le16(SMB2_COMPRESSION_FLAG_NONE)))
+			return -EINVAL;
 	}
 
 	return out_remaining ? -EINVAL : 0;
@@ -195,15 +198,22 @@ int smb_compression_decompress(__le16 alg, bool allow_chained,
 	const struct smb2_compression_hdr *hdr = src;
 
 	if (!src || !dst || slen < sizeof(*hdr) ||
-	    hdr->ProtocolId != SMB2_COMPRESSION_TRANSFORM_ID ||
-	    alg == SMB3_COMPRESS_NONE)
+	    hdr->ProtocolId != SMB2_COMPRESSION_TRANSFORM_ID)
 		return -EINVAL;
 
-	if (hdr->Flags == cpu_to_le16(SMB2_COMPRESSION_FLAG_CHAINED))
-		return smb_decompress_chained(alg, allow_chained, hdr, slen,
-					      dst, dlen);
+	/* If @allow_chained == true, the first payload hdr may have "NONE" algorithm */
+	if (unlikely(!allow_chained && (hdr->CompressionAlgorithm == SMB3_COMPRESS_NONE ||
+					hdr->CompressionAlgorithm == SMB3_COMPRESS_PATTERN)))
+		return -EINVAL;
+
+	if (hdr->Flags == cpu_to_le16(SMB2_COMPRESSION_FLAG_CHAINED)) {
+		if (likely(allow_chained))
+			return smb_decompress_chained(alg, hdr, slen, dst, dlen);
+
+		return -EINVAL;
+	}
 
-	if (hdr->Flags != cpu_to_le16(SMB2_COMPRESSION_FLAG_NONE))
+	if (unlikely(hdr->Flags != cpu_to_le16(SMB2_COMPRESSION_FLAG_NONE) || allow_chained))
 		return -EINVAL;
 
 	return smb_decompress_unchained(alg, hdr, slen, dst, dlen);
-- 
2.54.0