From 7084191d53b224b953c8e1db525ea6c31aca5fc7 Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@rowland.harvard.edu>
Date: Wed, 20 Feb 2008 14:15:58 -0500
Subject: [PATCH] USB: usb-storage: don't access beyond the end of the sg
buffer
This patch (as1035) fixes a bug in usb_stor_access_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. It also fixes up the formatting of a few comments
and similar whitespace issues.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
drivers/usb/storage/protocol.c | 27 +++++++++++++++------------
1 file changed, 15 insertions(+), 12 deletions(-)
diff --git a/drivers/usb/storage/protocol.c b/drivers/usb/storage/protocol.c
index a41ce21c069..958f5b17847 100644
--- a/drivers/usb/storage/protocol.c
+++ b/drivers/usb/storage/protocol.c
@@ -150,13 +150,14 @@ void usb_stor_transparent_scsi_command(struct scsi_cmnd *srb,
/* Copy a buffer of length buflen to/from the srb's transfer buffer.
* Update the **sgptr and *offset variables so that the next copy will
- * pick up from where this one left off. */
-
+ * pick up from where this one left off.
+ */
unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
unsigned int buflen, struct scsi_cmnd *srb, struct scatterlist **sgptr,
unsigned int *offset, enum xfer_buf_dir dir)
{
unsigned int cnt;
+ struct scatterlist *sg = *sgptr;
/* We have to go through the list one entry
* at a time. Each s-g entry contains some number of pages, and
@@ -164,22 +165,23 @@ unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
* in kernel-addressable memory then kmap() will return its address.
* If the page is not directly accessible -- such as a user buffer
* located in high memory -- then kmap() will map it to a temporary
- * position in the kernel's virtual address space. */
- struct scatterlist *sg = *sgptr;
+ * position in the kernel's virtual address space.
+ */
if (!sg)
sg = scsi_sglist(srb);
+ buflen = min(buflen, scsi_bufflen(srb));
/* This loop handles a single s-g list entry, which may
- * include multiple pages. Find the initial page structure
- * and the starting offset within the page, and update
- * the *offset and **sgptr values for the next loop. */
+ * include multiple pages. Find the initial page structure
+ * and the starting offset within the page, and update
+ * the *offset and **sgptr 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 =
- (sg->offset + *offset) & (PAGE_SIZE-1);
+ unsigned int poff = (sg->offset + *offset) & (PAGE_SIZE-1);
unsigned int sglen = sg->length - *offset;
if (sglen > buflen - cnt) {
@@ -222,14 +224,15 @@ unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
}
/* Store the contents of buffer into srb's transfer buffer and set the
- * SCSI residue. */
+ * SCSI residue.
+ */
void usb_stor_set_xfer_buf(unsigned char *buffer,
unsigned int buflen, struct scsi_cmnd *srb)
{
unsigned int offset = 0;
struct scatterlist *sg = NULL;
- usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset,
+ buflen = usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset,
TO_XFER_BUF);
if (buflen < scsi_bufflen(srb))
scsi_set_resid(srb, scsi_bufflen(srb) - buflen);
--
2.20.1