[PATCH 6.19 258/311] comedi: me4000: Fix potential overrun of firmware buffer

Greg Kroah-Hartman
2026-04-08T19:00:50Z

From: Ian Abbott <abbotti@mev.co.uk>

commit 3fb43a7a5b44713f892c58ead2e5f3a1bc9f4ee7 upstream.

`me4000_xilinx_download()` loads the firmware that was requested by
`request_firmware()`. It is possible for it to overrun the source
buffer because it blindly trusts the file format. It reads a data
stream length from the first 4 bytes into variable `file_length` and
reads the data stream contents of length `file_length` from offset 16
onwards.

Add a test to ensure that the supplied firmware is long enough to
contain the header and the data stream. On failure, log an error and
return `-EINVAL`.

Note: The firmware loading was totally broken before commit ac584af59945
("staging: comedi: me4000: fix firmware downloading"), but that is the
most sensible target for this fix.

Fixes: ac584af59945 ("staging: comedi: me4000: fix firmware downloading")
Cc: stable <stable@kernel.org>
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://patch.msgid.link/20260205133949.71722-1-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/comedi/drivers/me4000.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)

--- a/drivers/comedi/drivers/me4000.c
+++ b/drivers/comedi/drivers/me4000.c
@@ -315,6 +315,18 @@ static int me4000_xilinx_download(struct
unsigned int val;
unsigned int i;

+ /* Get data stream length from header. */
+ if (size >= 4) {
+ file_length = (((unsigned int)data[0] & 0xff) << 24) +
+ (((unsigned int)data[1] & 0xff) << 16) +
+ (((unsigned int)data[2] & 0xff) << 8) +
+ ((unsigned int)data[3] & 0xff);
+ }
+ if (size < 16 || file_length > size - 16) {
+ dev_err(dev->class_dev, "Firmware length inconsistency\n");
+ return -EINVAL;
+ }
+
if (!xilinx_iobase)
return -ENODEV;

@@ -346,10 +358,6 @@ static int me4000_xilinx_download(struct
outl(val, devpriv->plx_regbase + PLX9052_CNTRL);

/* Download Xilinx firmware */
- file_length = (((unsigned int)data[0] & 0xff) << 24) +
- (((unsigned int)data[1] & 0xff) << 16) +
- (((unsigned int)data[2] & 0xff) << 8) +
- ((unsigned int)data[3] & 0xff);
usleep_range(10, 1000);

for (i = 0; i < file_length; i++) {