FAILED: patch "[PATCH] smb: client: restrict implied bcc[0] exemption to responses" failed to apply to 5.15-stable tree

index 2a7355ce1a07..6270b33147d2 100644
@@ -19,6 +19,8 @@
 #include "nterr.h"
 #include "cached_dir.h"
 
+static unsigned int __smb2_calc_size(void *buf, bool *have_data);
+
 static int
 check_smb2_hdr(struct smb2_hdr *shdr, __u64 mid)
 {

@@ -145,6 +147,7 @@ smb2_check_message(char *buf, unsigned int pdu_len, unsigned int len,
 	int command;
 	__u32 calc_len; /* calculated length */
 	__u64 mid;
+	bool have_data;
 
 	/* If server is a channel, select the primary channel */
 	pserver = SERVER_IS_CHAN(server) ? server->primary_server : server;

@@ -228,7 +231,8 @@ smb2_check_message(char *buf, unsigned int pdu_len, unsigned int len,
 		}
 	}
 
-	calc_len = smb2_calc_size(buf);
+	have_data = false;
+	calc_len = __smb2_calc_size(buf, &have_data);
 
 	/* For SMB2_IOCTL, OutputOffset and OutputLength are optional, so might
 	 * be 0, and not a real miscalculation */

@@ -247,8 +251,13 @@ smb2_check_message(char *buf, unsigned int pdu_len, unsigned int len,
 		/* Windows 7 server returns 24 bytes more */
 		if (calc_len + 24 == len && command == SMB2_OPLOCK_BREAK_HE)
 			return 0;
-		/* server can return one byte more due to implied bcc[0] */
-		if (calc_len == len + 1)
+		/*
+		 * Server can return one byte more due to implied bcc[0].
+		 * Allow it only when there is no data area; if data_length > 0
+		 * the +1 gap indicates an overreported data length rather than
+		 * the bcc[0] omission.
+		 */
+		if (calc_len == len + 1 && !have_data)
 			return 0;
 
 		/*

@@ -409,14 +418,17 @@ smb2_get_data_area_len(int *off, int *len, struct smb2_hdr *shdr)
 /*
  * Calculate the size of the SMB message based on the fixed header
  * portion, the number of word parameters and the data portion of the message.
+ * If have_data is non-NULL, it is set to true when a non-empty data area was
+ * found (data_length > 0), allowing callers to distinguish the implied bcc[0]
+ * case (no data area) from an overreported data length.
  */
-unsigned int
-smb2_calc_size(void *buf)
+static unsigned int
+__smb2_calc_size(void *buf, bool *have_data)
 {
 	struct smb2_pdu *pdu = buf;
 	struct smb2_hdr *shdr = &pdu->hdr;
 	int offset; /* the offset from the beginning of SMB to data area */
-	int data_length; /* the length of the variable length data area */
+	int data_length = 0; /* the length of the variable length data area */
 	/* Structure Size has already been checked to make sure it is 64 */
 	int len = le16_to_cpu(shdr->StructureSize);
 

@@ -449,9 +461,17 @@ smb2_calc_size(void *buf)
 	}
 calc_size_exit:
 	cifs_dbg(FYI, "SMB2 len %d\n", len);
+	if (have_data)
+		*have_data = (data_length > 0);
 	return len;
 }
 
+unsigned int
+smb2_calc_size(void *buf)
+{
+	return __smb2_calc_size(buf, NULL);
+}
+
 /* Note: caller must free return buffer */
 __le16 *
 cifs_convert_path_to_utf16(const char *from, struct cifs_sb_info *cifs_sb)

index c254e714f7ceb9..8f5cca9b20177e 100644
@@ -38,7 +38,6 @@
 #include <linux/key-type.h>
 #include "cifs_spnego.h"
 #include "fscache.h"
-#include "smb2pdu.h"
 #ifdef CONFIG_CIFS_DFS_UPCALL
 #include "dfs_cache.h"
 #endif

index 68b9b382d44bf2..1030159152cc28 100644
@@ -22,6 +22,7 @@
 #include <crypto/internal/hash.h>
 #include <linux/scatterlist.h>
 #include <uapi/linux/cifs/cifs_mount.h>
+#include "../smbfs_common/smb2pdu.h"
 #include "smb2pdu.h"
 #include "smb2glob.h"
 

@@ -794,7 +795,7 @@ revert_current_mid(struct TCP_Server_Info *server, const unsigned int val)
 
 static inline void
 revert_current_mid_from_hdr(struct TCP_Server_Info *server,
-			    const struct smb2_sync_hdr *shdr)
+			    const struct smb2_hdr *shdr)
 {
 	unsigned int num = le16_to_cpu(shdr->CreditCharge);
 

index 5fd9098250906a..6fca381353620a 100644
@@ -722,7 +722,7 @@ dequeue_mid(struct mid_q_entry *mid, bool malformed)
 static unsigned int
 smb2_get_credits_from_hdr(char *buffer, struct TCP_Server_Info *server)
 {
-	struct smb2_sync_hdr *shdr = (struct smb2_sync_hdr *)buffer;
+	struct smb2_hdr *shdr = (struct smb2_hdr *)buffer;
 
 	/*
 	 * SMB1 does not use credits.

@@ -926,7 +926,7 @@ cifs_handle_standard(struct TCP_Server_Info *server, struct mid_q_entry *mid)
 static void
 smb2_add_credits_from_hdr(char *buffer, struct TCP_Server_Info *server)
 {
-	struct smb2_sync_hdr *shdr = (struct smb2_sync_hdr *)buffer;
+	struct smb2_hdr *shdr = (struct smb2_hdr *)buffer;
 	int scredits, in_flight;
 
 	/*

index a3d37e7769e61f..7fd5882671b6b9 100644
@@ -150,7 +150,7 @@ cifs_buf_get(void)
 	 * SMB2 header is bigger than CIFS one - no problems to clean some
 	 * more bytes for CIFS.
 	 */
-	size_t buf_size = sizeof(struct smb2_sync_hdr);
+	size_t buf_size = sizeof(struct smb2_hdr);
 
 	/*
 	 * We could use negotiated size instead of max_msgsize -

index 181514b8770dde..194799ddd38288 100644
@@ -2439,14 +2439,16 @@ smb2_print_status(__le32 status)
 int
 map_smb2_to_linux_error(char *buf, bool log_err)
 {
-	struct smb2_sync_hdr *shdr = (struct smb2_sync_hdr *)buf;
+	struct smb2_hdr *shdr = (struct smb2_hdr *)buf;
 	unsigned int i;
 	int rc = -EIO;
 	__le32 smb2err = shdr->Status;
 
 	if (smb2err == 0) {
-		trace_smb3_cmd_done(shdr->TreeId, shdr->SessionId,
-			le16_to_cpu(shdr->Command), le64_to_cpu(shdr->MessageId));
+		trace_smb3_cmd_done(le32_to_cpu(shdr->Id.SyncId.TreeId),
+			      le64_to_cpu(shdr->SessionId),
+			      le16_to_cpu(shdr->Command),
+			      le64_to_cpu(shdr->MessageId));
 		return 0;
 	}
 

@@ -2470,8 +2472,10 @@ map_smb2_to_linux_error(char *buf, bool log_err)
 	cifs_dbg(FYI, "Mapping SMB2 status code 0x%08x to POSIX err %d\n",
 		 __le32_to_cpu(smb2err), rc);
 
-	trace_smb3_cmd_err(shdr->TreeId, shdr->SessionId,
-			le16_to_cpu(shdr->Command),
-			le64_to_cpu(shdr->MessageId), le32_to_cpu(smb2err), rc);
+	trace_smb3_cmd_err(le32_to_cpu(shdr->Id.SyncId.TreeId),
+			   le64_to_cpu(shdr->SessionId),
+			   le16_to_cpu(shdr->Command),
+			   le64_to_cpu(shdr->MessageId),
+			   le32_to_cpu(smb2err), rc);
 	return rc;
 }

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index ada1d7338f34f6..b8f7abbf9dacd7 100644
@@ -25,7 +25,7 @@ extern int smb2_check_message(char *buf, unsigned int length,
 			      struct TCP_Server_Info *server);
 extern unsigned int smb2_calc_size(void *buf, struct TCP_Server_Info *server);
 extern char *smb2_get_data_area_len(int *off, int *len,
-				    struct smb2_sync_hdr *shdr);
+				    struct smb2_hdr *shdr);
 extern __le16 *cifs_convert_path_to_utf16(const char *from,
 					  struct cifs_sb_info *cifs_sb);
 

index f1e981328bc874..96a6a1c0cc07d4 100644
@@ -19,7 +19,6 @@
 #include <linux/mempool.h>
 #include <linux/highmem.h>
 #include <crypto/aead.h>
-#include "smb2pdu.h"
 #include "cifsglob.h"
 #include "cifsproto.h"
 #include "smb2proto.h"

@@ -213,14 +212,14 @@ smb2_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server,
 	unsigned char smb2_signature[SMB2_HMACSHA256_SIZE];
 	unsigned char *sigptr = smb2_signature;
 	struct kvec *iov = rqst->rq_iov;
-	struct smb2_sync_hdr *shdr = (struct smb2_sync_hdr *)iov[0].iov_base;
+	struct smb2_hdr *shdr = (struct smb2_hdr *)iov[0].iov_base;
 	struct cifs_ses *ses;
 	struct shash_desc *shash;
 	struct crypto_shash *hash;
 	struct sdesc *sdesc = NULL;
 	struct smb_rqst drqst;
 
-	ses = smb2_find_smb_ses(server, shdr->SessionId);
+	ses = smb2_find_smb_ses(server, le64_to_cpu(shdr->SessionId));
 	if (unlikely(!ses)) {
 		cifs_server_dbg(VFS, "%s: Could not find session\n", __func__);
 		return -ENOENT;

@@ -549,14 +548,14 @@ smb3_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server,
 	unsigned char smb3_signature[SMB2_CMACAES_SIZE];
 	unsigned char *sigptr = smb3_signature;
 	struct kvec *iov = rqst->rq_iov;
-	struct smb2_sync_hdr *shdr = (struct smb2_sync_hdr *)iov[0].iov_base;
+	struct smb2_hdr *shdr = (struct smb2_hdr *)iov[0].iov_base;
 	struct shash_desc *shash;
 	struct crypto_shash *hash;
 	struct sdesc *sdesc = NULL;
 	struct smb_rqst drqst;
 	u8 key[SMB3_SIGN_KEY_SIZE];
 
-	rc = smb2_get_sign_key(shdr->SessionId, server, key);
+	rc = smb2_get_sign_key(le64_to_cpu(shdr->SessionId), server, key);
 	if (unlikely(rc)) {
 		cifs_server_dbg(VFS, "%s: Could not get signing key\n", __func__);
 		return rc;

@@ -628,12 +627,12 @@ static int
 smb2_sign_rqst(struct smb_rqst *rqst, struct TCP_Server_Info *server)
 {
 	int rc = 0;
-	struct smb2_sync_hdr *shdr;
+	struct smb2_hdr *shdr;
 	struct smb2_sess_setup_req *ssr;
 	bool is_binding;
 	bool is_signed;
 
-	shdr = (struct smb2_sync_hdr *)rqst->rq_iov[0].iov_base;
+	shdr = (struct smb2_hdr *)rqst->rq_iov[0].iov_base;
 	ssr = (struct smb2_sess_setup_req *)shdr;
 
 	is_binding = shdr->Command == SMB2_SESSION_SETUP &&

@@ -659,8 +658,8 @@ smb2_verify_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
 {
 	unsigned int rc;
 	char server_response_sig[SMB2_SIGNATURE_SIZE];
-	struct smb2_sync_hdr *shdr =
-			(struct smb2_sync_hdr *)rqst->rq_iov[0].iov_base;
+	struct smb2_hdr *shdr =
+			(struct smb2_hdr *)rqst->rq_iov[0].iov_base;
 
 	if ((shdr->Command == SMB2_NEGOTIATE) ||
 	    (shdr->Command == SMB2_SESSION_SETUP) ||

@@ -706,7 +705,7 @@ smb2_verify_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
  */
 static inline void
 smb2_seq_num_into_buf(struct TCP_Server_Info *server,
-		      struct smb2_sync_hdr *shdr)
+		      struct smb2_hdr *shdr)
 {
 	unsigned int i, num = le16_to_cpu(shdr->CreditCharge);
 

@@ -717,7 +716,7 @@ smb2_seq_num_into_buf(struct TCP_Server_Info *server,
 }
 
 static struct mid_q_entry *
-smb2_mid_entry_alloc(const struct smb2_sync_hdr *shdr,
+smb2_mid_entry_alloc(const struct smb2_hdr *shdr,
 		     struct TCP_Server_Info *server)
 {
 	struct mid_q_entry *temp;

@@ -749,14 +748,15 @@ smb2_mid_entry_alloc(const struct smb2_sync_hdr *shdr,
 
 	atomic_inc(&midCount);
 	temp->mid_state = MID_REQUEST_ALLOCATED;
-	trace_smb3_cmd_enter(shdr->TreeId, shdr->SessionId,
-		le16_to_cpu(shdr->Command), temp->mid);
+	trace_smb3_cmd_enter(le32_to_cpu(shdr->Id.SyncId.TreeId),
+			     le64_to_cpu(shdr->SessionId),
+			     le16_to_cpu(shdr->Command), temp->mid);
 	return temp;
 }
 
 static int
 smb2_get_mid_entry(struct cifs_ses *ses, struct TCP_Server_Info *server,
-		   struct smb2_sync_hdr *shdr, struct mid_q_entry **mid)
+		   struct smb2_hdr *shdr, struct mid_q_entry **mid)
 {
 	if (server->tcpStatus == CifsExiting)
 		return -ENOENT;

@@ -824,8 +824,8 @@ smb2_setup_request(struct cifs_ses *ses, struct TCP_Server_Info *server,
 		   struct smb_rqst *rqst)
 {
 	int rc;
-	struct smb2_sync_hdr *shdr =
-			(struct smb2_sync_hdr *)rqst->rq_iov[0].iov_base;
+	struct smb2_hdr *shdr =
+			(struct smb2_hdr *)rqst->rq_iov[0].iov_base;
 	struct mid_q_entry *mid;
 
 	smb2_seq_num_into_buf(server, shdr);

@@ -850,8 +850,8 @@ struct mid_q_entry *
 smb2_setup_async_request(struct TCP_Server_Info *server, struct smb_rqst *rqst)
 {
 	int rc;
-	struct smb2_sync_hdr *shdr =
-			(struct smb2_sync_hdr *)rqst->rq_iov[0].iov_base;
+	struct smb2_hdr *shdr =
+			(struct smb2_hdr *)rqst->rq_iov[0].iov_base;
 	struct mid_q_entry *mid;
 
 	if (server->tcpStatus == CifsNeedNegotiate &&

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index db83485d28d932..ab20585db8c159 100644
@@ -150,16 +150,18 @@ smb2_check_message(char *buf, unsigned int len, struct TCP_Server_Info *srvr)
 		struct smb2_transform_hdr *thdr =
 			(struct smb2_transform_hdr *)buf;
 		struct cifs_ses *ses = NULL;
+		struct cifs_ses *iter;
 
 		/* decrypt frame now that it is completely read in */
 		spin_lock(&cifs_tcp_ses_lock);
-		list_for_each_entry(ses, &srvr->smb_ses_list, smb_ses_list) {
-			if (ses->Suid == le64_to_cpu(thdr->SessionId))
+		list_for_each_entry(iter, &srvr->smb_ses_list, smb_ses_list) {
+			if (iter->Suid == le64_to_cpu(thdr->SessionId)) {
+				ses = iter;
 				break;
+			}
 		}
 		spin_unlock(&cifs_tcp_ses_lock);
-		if (list_entry_is_head(ses, &srvr->smb_ses_list,
-				       smb_ses_list)) {
+		if (!ses) {
 			cifs_dbg(VFS, "no decryption - session id not found\n");
 			return 1;
 		}

index 6fca381353620a..e29314719bc26b 100644
@@ -890,19 +890,18 @@ int
 cifs_handle_standard(struct TCP_Server_Info *server, struct mid_q_entry *mid)
 {
 	char *buf = server->large_buf ? server->bigbuf : server->smallbuf;
-	int length;
+	int rc;
 
 	/*
 	 * We know that we received enough to get to the MID as we
 	 * checked the pdu_length earlier. Now check to see
-	 * if the rest of the header is OK. We borrow the length
-	 * var for the rest of the loop to avoid a new stack var.
+	 * if the rest of the header is OK.
 	 *
 	 * 48 bytes is enough to display the header and a little bit
 	 * into the payload for debugging purposes.
 	 */
-	length = server->ops->check_message(buf, server->total_read, server);
-	if (length != 0)
+	rc = server->ops->check_message(buf, server->total_read, server);
+	if (rc)
 		cifs_dump_mem("Bad SMB: ", buf,
 			min_t(unsigned int, server->total_read, 48));
 

@@ -917,9 +916,9 @@ cifs_handle_standard(struct TCP_Server_Info *server, struct mid_q_entry *mid)
 		return -1;
 
 	if (!mid)
-		return length;
+		return rc;
 
-	handle_mid(mid, server, buf, length);
+	handle_mid(mid, server, buf, rc);
 	return 0;
 }
 

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index dd39097027b5f3..b7bbcd67e09545 100644
@@ -42,7 +42,7 @@ void cifs_dump_detail(void *buf, struct TCP_Server_Info *server)
 		 smb->Command, smb->Status.CifsError,
 		 smb->Flags, smb->Flags2, smb->Mid, smb->Pid);
 	cifs_dbg(VFS, "smb buf %p len %u\n", smb,
-		 server->ops->calc_smb_size(smb, server));
+		 server->ops->calc_smb_size(smb));
 #endif /* CONFIG_CIFS_DEBUG2 */
 }
 

index 1030159152cc28..136f8b9cb44454 100644
@@ -389,7 +389,7 @@ struct smb_version_operations {
 	int (*close_dir)(const unsigned int, struct cifs_tcon *,
 			 struct cifs_fid *);
 	/* calculate a size of SMB message */
-	unsigned int (*calc_smb_size)(void *buf, struct TCP_Server_Info *ptcpi);
+	unsigned int (*calc_smb_size)(void *buf);
 	/* check for STATUS_PENDING and process the response if yes */
 	bool (*is_status_pending)(char *buf, struct TCP_Server_Info *server);
 	/* check for STATUS_NETWORK_SESSION_EXPIRED */

index 7d00802f972239..3de85b3283e627 100644
@@ -148,7 +148,7 @@ extern int cifs_get_writable_path(struct cifs_tcon *tcon, const char *name,
 extern struct cifsFileInfo *find_readable_file(struct cifsInodeInfo *, bool);
 extern int cifs_get_readable_path(struct cifs_tcon *tcon, const char *name,
 				  struct cifsFileInfo **ret_file);
-extern unsigned int smbCalcSize(void *buf, struct TCP_Server_Info *server);
+extern unsigned int smbCalcSize(void *buf);
 extern int decode_negTokenInit(unsigned char *security_blob, int length,
 			struct TCP_Server_Info *server);
 extern int cifs_convert_address(struct sockaddr *dst, const char *src, int len);

index 7fd5882671b6b9..8b0eeb9ae7926e 100644
@@ -357,7 +357,7 @@ checkSMB(char *buf, unsigned int total_read, struct TCP_Server_Info *server)
 	/* otherwise, there is enough to get to the BCC */
 	if (check_smb_hdr(smb))
 		return -EIO;
-	clc_len = smbCalcSize(smb, server);
+	clc_len = smbCalcSize(smb);
 
 	if (4 + rfclen != total_read) {
 		cifs_dbg(VFS, "Length read does not match RFC1001 length %d\n",

index fa9fbd6a819cb8..6ddab41f587385 100644
@@ -912,7 +912,7 @@ map_and_check_smb_error(struct mid_q_entry *mid, bool logErr)
  * portion, the number of word parameters and the data portion of the message
  */
 unsigned int
-smbCalcSize(void *buf, struct TCP_Server_Info *server)
+smbCalcSize(void *buf)
 {
 	struct smb_hdr *ptr = (struct smb_hdr *)buf;
 	return (sizeof(struct smb_hdr) + (2 * ptr->WordCount) +

index 6aa3c267f4ca41..7c47a03afbcc39 100644
@@ -808,8 +808,7 @@ find_cifs_entry(const unsigned int xid, struct cifs_tcon *tcon, loff_t pos,
 
 		end_of_smb = cfile->srch_inf.ntwrk_buf_start +
 			server->ops->calc_smb_size(
-					cfile->srch_inf.ntwrk_buf_start,
-					server);
+					cfile->srch_inf.ntwrk_buf_start);
 
 		cur_ent = cfile->srch_inf.srch_entries_start;
 		first_entry_in_buffer = cfile->srch_inf.index_of_last_entry

@@ -1008,8 +1007,7 @@ int cifs_readdir(struct file *file, struct dir_context *ctx)
 	cifs_dbg(FYI, "loop through %d times filling dir for net buf %p\n",
 		 num_to_fill, cifsFile->srch_inf.ntwrk_buf_start);
 	max_len = tcon->ses->server->ops->calc_smb_size(
-			cifsFile->srch_inf.ntwrk_buf_start,
-			tcon->ses->server);
+			cifsFile->srch_inf.ntwrk_buf_start);
 	end_of_smb = cifsFile->srch_inf.ntwrk_buf_start + max_len;
 
 	tmp_buf = kmalloc(UNICODE_NAME_MAX, GFP_KERNEL);

index c24d3bcb565f17..29d723c04b1666 100644
@@ -221,7 +221,7 @@ smb2_check_message(char *buf, unsigned int len, struct TCP_Server_Info *server)
 		}
 	}
 
-	calc_len = smb2_calc_size(buf, server);
+	calc_len = smb2_calc_size(buf);
 
 	/* For SMB2_IOCTL, OutputOffset and OutputLength are optional, so might
 	 * be 0, and not a real miscalculation */

@@ -403,7 +403,7 @@ smb2_get_data_area_len(int *off, int *len, struct smb2_hdr *shdr)
  * portion, the number of word parameters and the data portion of the message.
  */
 unsigned int
-smb2_calc_size(void *buf, struct TCP_Server_Info *srvr)
+smb2_calc_size(void *buf)
 {
 	struct smb2_pdu *pdu = (struct smb2_pdu *)buf;
 	struct smb2_hdr *shdr = &pdu->hdr;

index 2a640015c261bf..b17b5aa3fdb2f4 100644
@@ -374,7 +374,7 @@ smb2_dump_detail(void *buf, struct TCP_Server_Info *server)
 		 shdr->Command, shdr->Status, shdr->Flags, shdr->MessageId,
 		 shdr->Id.SyncId.ProcessId);
 	cifs_server_dbg(VFS, "smb buf %p len %u\n", buf,
-		 server->ops->calc_smb_size(buf, server));
+		 server->ops->calc_smb_size(buf));
 #endif
 }
 

index b8f7abbf9dacd7..73955013033c04 100644
@@ -23,7 +23,7 @@ struct smb_rqst;
 extern int map_smb2_to_linux_error(char *buf, bool log_err);
 extern int smb2_check_message(char *buf, unsigned int length,
 			      struct TCP_Server_Info *server);
-extern unsigned int smb2_calc_size(void *buf, struct TCP_Server_Info *server);
+extern unsigned int smb2_calc_size(void *buf);
 extern char *smb2_get_data_area_len(int *off, int *len,
 				    struct smb2_hdr *shdr);
 extern __le16 *cifs_convert_path_to_utf16(const char *from,

index 29d723c04b1666..0db16730dccab9 100644
@@ -17,6 +17,8 @@
 #include "smb2glob.h"
 #include "nterr.h"
 
+static unsigned int __smb2_calc_size(void *buf, bool *have_data);
+
 static int
 check_smb2_hdr(struct smb2_hdr *shdr, __u64 mid)
 {

@@ -141,6 +143,7 @@ smb2_check_message(char *buf, unsigned int len, struct TCP_Server_Info *server)
 	int command;
 	__u32 calc_len; /* calculated length */
 	__u64 mid;
+	bool have_data;
 
 	/*
 	 * Add function to do table lookup of StructureSize by command

@@ -221,7 +224,8 @@ smb2_check_message(char *buf, unsigned int len, struct TCP_Server_Info *server)
 		}
 	}
 
-	calc_len = smb2_calc_size(buf);
+	have_data = false;
+	calc_len = __smb2_calc_size(buf, &have_data);
 
 	/* For SMB2_IOCTL, OutputOffset and OutputLength are optional, so might
 	 * be 0, and not a real miscalculation */

@@ -239,8 +243,13 @@ smb2_check_message(char *buf, unsigned int len, struct TCP_Server_Info *server)
 		/* Windows 7 server returns 24 bytes more */
 		if (calc_len + 24 == len && command == SMB2_OPLOCK_BREAK_HE)
 			return 0;
-		/* server can return one byte more due to implied bcc[0] */
-		if (calc_len == len + 1)
+		/*
+		 * Server can return one byte more due to implied bcc[0].
+		 * Allow it only when there is no data area; if data_length > 0
+		 * the +1 gap indicates an overreported data length rather than
+		 * the bcc[0] omission.
+		 */
+		if (calc_len == len + 1 && !have_data)
 			return 0;
 
 		/*

@@ -401,14 +410,17 @@ smb2_get_data_area_len(int *off, int *len, struct smb2_hdr *shdr)
 /*
  * Calculate the size of the SMB message based on the fixed header
  * portion, the number of word parameters and the data portion of the message.
+ * If have_data is non-NULL, it is set to true when a non-empty data area was
+ * found (data_length > 0), allowing callers to distinguish the implied bcc[0]
+ * case (no data area) from an overreported data length.
  */
-unsigned int
-smb2_calc_size(void *buf)
+static unsigned int
+__smb2_calc_size(void *buf, bool *have_data)
 {
 	struct smb2_pdu *pdu = (struct smb2_pdu *)buf;
 	struct smb2_hdr *shdr = &pdu->hdr;
 	int offset; /* the offset from the beginning of SMB to data area */
-	int data_length; /* the length of the variable length data area */
+	int data_length = 0; /* the length of the variable length data area */
 	/* Structure Size has already been checked to make sure it is 64 */
 	int len = le16_to_cpu(shdr->StructureSize);
 

@@ -441,9 +453,17 @@ smb2_calc_size(void *buf)
 	}
 calc_size_exit:
 	cifs_dbg(FYI, "SMB2 len %d\n", len);
+	if (have_data)
+		*have_data = (data_length > 0);
 	return len;
 }
 
+unsigned int
+smb2_calc_size(void *buf)
+{
+	return __smb2_calc_size(buf, NULL);
+}
+
 /* Note: caller must free return buffer */
 __le16 *
 cifs_convert_path_to_utf16(const char *from, struct cifs_sb_info *cifs_sb)