[PATCH 5.4 047/408] SMB3: Resolve data corruption of TCP server info fields

Greg Kroah-Hartman
2020-10-27T17:43:04Z

From: Rohith Surabattula <rohiths@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 <rohiths@microsoft.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
CC: Stable <stable@vger.kernel.org> #5.4+
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -3886,7 +3886,8 @@ 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};
@@ -3912,7 +3913,8 @@ 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;
}
@@ -4126,7 +4128,7 @@ 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;
@@ -4232,7 +4234,7 @@ 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;

@@ -4288,7 +4290,7 @@ 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;