usb-storage: don't access beyond the end of the sg buffer

This patch (as1038) fixes a bug in usb_stor_access_xfer_buf() and
usb_stor_set_xfer_buf() (the bug was originally found by Boaz
Harrosh): The routine must not attempt to write beyond the end of a
scatter-gather list or beyond the number of bytes requested.

This is the minimal 2.6.24 equivalent to as1035 +
as1037 (7084191d53b224b953c8e1db525ea6c31aca5fc7 "USB:
usb-storage: don't access beyond the end of the sg buffer" +
6d512a80c26d87f8599057c86dc920fbfe0aa3aa "usb-storage: update earlier
scatter-gather bug fix").  Mark Glines has confirmed that it fixes
his problem.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Mark Glines <mark@glines.org>
Cc: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/storage/protocol.c b/drivers/usb/storage/protocol.c
index 889622baac20ff917f7f3d98c7251f24c10a0e2f..45262f309dcb6e39fe6bfc7661895c66fc8ea462 100644 (file)
--- a/drivers/usb/storage/protocol.c
+++ b/drivers/usb/storage/protocol.c
@@ -194,7 +194,7 @@ unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
                 * and the starting offset within the page, and update
                 * the *offset and *index values for the next loop. */
                cnt = 0;
-               while (cnt < buflen) {
+               while (cnt < buflen && sg) {
                        struct page *page = sg_page(sg) +
                                        ((sg->offset + *offset) >> PAGE_SHIFT);
                        unsigned int poff =
@@ -249,7 +249,8 @@ void usb_stor_set_xfer_buf(unsigned char *buffer,
        unsigned int offset = 0;
        struct scatterlist *sg = NULL;
 
-       usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset,
+       buflen = min(buflen, srb->request_bufflen);
+       buflen = usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset,
                        TO_XFER_BUF);
        if (buflen < srb->request_bufflen)
                srb->resid = srb->request_bufflen - buflen;