[PATCH 5.9 068/757] SMB3: Resolve data corruption of TCP server info fields

[Greg Kroah-Hartman]

From: Rohith Surabattula <rohi...@microsoft.com>

commit 62593011247c8a8cfeb0c86aff84688b196727c2 upstream.

TCP server info field server->total_read is modified in parallel by
demultiplex thread and decrypt offload worker thread. server->total_read
is used in calculation to discard the remaining data of PDU which is
not read into memory.

Because of parallel modification, server->total_read can get corrupted
and can result in discarding the valid data of next PDU.

Signed-off-by: Rohith Surabattula <rohi...@microsoft.com>
Reviewed-by: Aurelien Aptel <aap...@suse.com>
Reviewed-by: Pavel Shilovsky <pshi...@microsoft.com>
CC: Stable <sta...@vger.kernel.org> #5.4+
Signed-off-by: Steve French <stfre...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 fs/cifs/smb2ops.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -4103,7 +4103,8 @@ smb3_is_transform_hdr(void *buf)
 static int
 decrypt_raw_data(struct TCP_Server_Info *server, char *buf,
                 unsigned int buf_data_size, struct page **pages,
-                unsigned int npages, unsigned int page_data_size)
+                unsigned int npages, unsigned int page_data_size,
+                bool is_offloaded)
 {
        struct kvec iov[2];
        struct smb_rqst rqst = {NULL};
@@ -4129,7 +4130,8 @@ decrypt_raw_data(struct TCP_Server_Info
 
        memmove(buf, iov[1].iov_base, buf_data_size);
 
-       server->total_read = buf_data_size + page_data_size;
+       if (!is_offloaded)
+               server->total_read = buf_data_size + page_data_size;
 
        return rc;
 }
@@ -4342,7 +4344,7 @@ static void smb2_decrypt_offload(struct
        struct mid_q_entry *mid;
 
        rc = decrypt_raw_data(dw->server, dw->buf, 
dw->server->vals->read_rsp_size,
-                             dw->ppages, dw->npages, dw->len);
+                             dw->ppages, dw->npages, dw->len, true);
        if (rc) {
                cifs_dbg(VFS, "error decrypting rc=%d\n", rc);
                goto free_pages;
@@ -4448,7 +4450,7 @@ receive_encrypted_read(struct TCP_Server
 
 non_offloaded_decrypt:
        rc = decrypt_raw_data(server, buf, server->vals->read_rsp_size,
-                             pages, npages, len);
+                             pages, npages, len, false);
        if (rc)
                goto free_pages;
 
@@ -4504,7 +4506,7 @@ receive_encrypted_standard(struct TCP_Se
        server->total_read += length;
 
        buf_size = pdu_length - sizeof(struct smb2_transform_hdr);
-       length = decrypt_raw_data(server, buf, buf_size, NULL, 0, 0);
+       length = decrypt_raw_data(server, buf, buf_size, NULL, 0, 0, false);
        if (length)
                return length;