The patch below does not apply to the 4.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 350be257ea83029daee974c72b1fe2e6f1f8e615 Mon Sep 17 00:00:00 2001 From: Pavel Shilovsky <pshilov@xxxxxxxxxxxxx> Date: Mon, 10 Apr 2017 10:31:33 -0700 Subject: [PATCH] CIFS: Fix null pointer deref during read resp processing Currently during receiving a read response mid->resp_buf can be NULL when it is being passed to cifs_discard_remaining_data() from cifs_readv_discard(). Fix it by always passing server->smallbuf instead and initializing mid->resp_buf at the end of read response processing. Signed-off-by: Pavel Shilovsky <pshilov@xxxxxxxxxxxxx> CC: Stable <stable@xxxxxxxxxxxxxxx> Acked-by: Sachin Prabhu <sprabhu@xxxxxxxxxx> Signed-off-by: Steve French <smfrench@xxxxxxxxx> diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h index ec5e5e514fdd..97e5d236d265 100644 --- a/fs/cifs/cifsproto.h +++ b/fs/cifs/cifsproto.h @@ -79,8 +79,7 @@ extern void cifs_delete_mid(struct mid_q_entry *mid); extern void cifs_wake_up_task(struct mid_q_entry *mid); extern int cifs_handle_standard(struct TCP_Server_Info *server, struct mid_q_entry *mid); -extern int cifs_discard_remaining_data(struct TCP_Server_Info *server, - char *buf); +extern int cifs_discard_remaining_data(struct TCP_Server_Info *server); extern int cifs_call_async(struct TCP_Server_Info *server, struct smb_rqst *rqst, mid_receive_t *receive, mid_callback_t *callback, diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c index 967b92631807..5d21f00ae341 100644 --- a/fs/cifs/cifssmb.c +++ b/fs/cifs/cifssmb.c @@ -1400,9 +1400,9 @@ CIFS_open(const unsigned int xid, struct cifs_open_parms *oparms, int *oplock, * current bigbuf. */ int -cifs_discard_remaining_data(struct TCP_Server_Info *server, char *buf) +cifs_discard_remaining_data(struct TCP_Server_Info *server) { - unsigned int rfclen = get_rfc1002_length(buf); + unsigned int rfclen = get_rfc1002_length(server->smallbuf); int remaining = rfclen + 4 - server->total_read; while (remaining > 0) { @@ -1426,8 +1426,10 @@ cifs_readv_discard(struct TCP_Server_Info *server, struct mid_q_entry *mid) int length; struct cifs_readdata *rdata = mid->callback_data; - length = cifs_discard_remaining_data(server, mid->resp_buf); + length = cifs_discard_remaining_data(server); dequeue_mid(mid, rdata->result); + mid->resp_buf = server->smallbuf; + server->smallbuf = NULL; return length; } @@ -1459,7 +1461,7 @@ cifs_readv_receive(struct TCP_Server_Info *server, struct mid_q_entry *mid) if (server->ops->is_status_pending && server->ops->is_status_pending(buf, server, 0)) { - cifs_discard_remaining_data(server, buf); + cifs_discard_remaining_data(server); return -1; } @@ -1519,9 +1521,6 @@ cifs_readv_receive(struct TCP_Server_Info *server, struct mid_q_entry *mid) cifs_dbg(FYI, "0: iov_base=%p iov_len=%u\n", rdata->iov[0].iov_base, server->total_read); - mid->resp_buf = server->smallbuf; - server->smallbuf = NULL; - /* how much data is in the response? */ data_len = server->ops->read_data_length(buf); if (data_offset + data_len > buflen) { @@ -1544,6 +1543,8 @@ cifs_readv_receive(struct TCP_Server_Info *server, struct mid_q_entry *mid) return cifs_readv_discard(server, mid); dequeue_mid(mid, false); + mid->resp_buf = server->smallbuf; + server->smallbuf = NULL; return length; } diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c index 7b12a727947e..152e37f2ad92 100644 --- a/fs/cifs/smb2ops.c +++ b/fs/cifs/smb2ops.c @@ -2195,7 +2195,7 @@ receive_encrypted_read(struct TCP_Server_Info *server, struct mid_q_entry **mid) if (rc) goto free_pages; - rc = cifs_discard_remaining_data(server, buf); + rc = cifs_discard_remaining_data(server); if (rc) goto free_pages; @@ -2221,7 +2221,7 @@ receive_encrypted_read(struct TCP_Server_Info *server, struct mid_q_entry **mid) kfree(pages); return rc; discard_data: - cifs_discard_remaining_data(server, buf); + cifs_discard_remaining_data(server); goto free_pages; }