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Subject[PATCH] staging: gs_fpgaboot: add buffer overflow checks
Date
Four fields in struct fpgaimage are char arrays of length MAX_STR (256).
The amount of data read into these buffers is controlled by a length
field in the bitstream file read from userspace. If a corrupt or
malicious firmware file was supplied, kernel data beyond these buffers
can be overwritten arbitrarily.

This patch adds a check of the bitstream's length value to ensure it
fits within the bounds of the allocated buffers. An error condition is
returned from gs_read_bitstream if any of the reads fail.

This patch also fixes a checkpatch.pl CHECK in io.c by removing the FSF
address paragraph.

Signed-off-by: Jacob von Chorus <jacobvonchorus@cwphoto.ca>
---
drivers/staging/gs_fpgaboot/gs_fpgaboot.c | 39 ++++++++++++++++++++++---------
drivers/staging/gs_fpgaboot/io.c | 4 ----
2 files changed, 28 insertions(+), 15 deletions(-)

diff --git a/drivers/staging/gs_fpgaboot/gs_fpgaboot.c b/drivers/staging/gs_fpgaboot/gs_fpgaboot.c
index 19b550fff0..2aafd769b8 100644
--- a/drivers/staging/gs_fpgaboot/gs_fpgaboot.c
+++ b/drivers/staging/gs_fpgaboot/gs_fpgaboot.c
@@ -47,7 +47,7 @@ static void read_bitstream(char *bitdata, char *buf, int *offset, int rdsize)
*offset += rdsize;
}

-static void readinfo_bitstream(char *bitdata, char *buf, int *offset)
+static int readinfo_bitstream(char *bitdata, char *buf, int n, int *offset)
{
char tbuf[64];
s32 len;
@@ -59,9 +59,15 @@ static void readinfo_bitstream(char *bitdata, char *buf, int *offset)
read_bitstream(bitdata, tbuf, offset, 2);

len = tbuf[0] << 8 | tbuf[1];
+ if (len + 1 > n) {
+ pr_err("error: readinfo buffer too small\n");
+ return -1;
+ }

read_bitstream(bitdata, buf, offset, len);
buf[len] = '\0';
+
+ return 0;
}

/*
@@ -113,7 +119,7 @@ static int readmagic_bitstream(char *bitdata, int *offset)
/*
* NOTE: supports only bitstream format
*/
-static enum fmt_image get_imageformat(struct fpgaimage *fimage)
+static enum fmt_image get_imageformat(void)
{
return f_bit;
}
@@ -127,7 +133,7 @@ static void gs_print_header(struct fpgaimage *fimage)
pr_info("lendata: %d\n", fimage->lendata);
}

-static void gs_read_bitstream(struct fpgaimage *fimage)
+static int gs_read_bitstream(struct fpgaimage *fimage)
{
char *bitdata;
int offset;
@@ -135,26 +141,37 @@ static void gs_read_bitstream(struct fpgaimage *fimage)
offset = 0;
bitdata = (char *)fimage->fw_entry->data;

- readmagic_bitstream(bitdata, &offset);
- readinfo_bitstream(bitdata, fimage->filename, &offset);
- readinfo_bitstream(bitdata, fimage->part, &offset);
- readinfo_bitstream(bitdata, fimage->date, &offset);
- readinfo_bitstream(bitdata, fimage->time, &offset);
- readlength_bitstream(bitdata, &fimage->lendata, &offset);
+ if (readmagic_bitstream(bitdata, &offset))
+ return -1;
+
+ if (readinfo_bitstream(bitdata, fimage->filename, MAX_STR, &offset))
+ return -1;
+ if (readinfo_bitstream(bitdata, fimage->part, MAX_STR, &offset))
+ return -1;
+ if (readinfo_bitstream(bitdata, fimage->date, MAX_STR, &offset))
+ return -1;
+ if (readinfo_bitstream(bitdata, fimage->time, MAX_STR, &offset))
+ return -1;
+
+ if (readlength_bitstream(bitdata, &fimage->lendata, &offset))
+ return -1;

fimage->fpgadata = bitdata + offset;
+
+ return 0;
}

static int gs_read_image(struct fpgaimage *fimage)
{
int img_fmt;

- img_fmt = get_imageformat(fimage);
+ img_fmt = get_imageformat();

switch (img_fmt) {
case f_bit:
pr_info("image is bitstream format\n");
- gs_read_bitstream(fimage);
+ if (gs_read_bitstream(fimage))
+ return -1;
break;
default:
pr_err("unsupported fpga image format\n");
diff --git a/drivers/staging/gs_fpgaboot/io.c b/drivers/staging/gs_fpgaboot/io.c
index c9391198fb..83a13ca725 100644
--- a/drivers/staging/gs_fpgaboot/io.c
+++ b/drivers/staging/gs_fpgaboot/io.c
@@ -9,10 +9,6 @@
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
*
* GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include <linux/kernel.h>
--
2.11.0
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