From: Marcel Holtmann <[EMAIL PROTECTED]>
Based on a patch from Don Howard <[EMAIL PROTECTED]>
When calling write() with a buffer larger than 512 bytes, the
driver's write buffer overflows, allowing to overwrite the EIP and
execute arbitrary code with kernel privileges.
In read(), there exists a similar problem, but coming from the device.
A malicous or buggy device sending more than 512 bytes can overflow
of the driver's read buffer, with the same effects as above.
Signed-off-by: Marcel Holtmann <[EMAIL PROTECTED]>
Signed-off-by: Harald Welte <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
Signed-off-by: Chris Wright <[EMAIL PROTECTED]>
---
drivers/char/pcmcia/cm4040_cs.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- linux-2.6.20.1.orig/drivers/char/pcmcia/cm4040_cs.c
+++ linux-2.6.20.1/drivers/char/pcmcia/cm4040_cs.c
@@ -273,6 +273,7 @@ static ssize_t cm4040_read(struct file *
DEBUGP(6, dev, "BytesToRead=%lu\n", bytes_to_read);
min_bytes_to_read = min(count, bytes_to_read + 5);
+ min_bytes_to_read = min_t(size_t, min_bytes_to_read,
READ_WRITE_BUFFER_SIZE);
DEBUGP(6, dev, "Min=%lu\n", min_bytes_to_read);
@@ -340,7 +341,7 @@ static ssize_t cm4040_write(struct file
return 0;
}
- if (count < 5) {
+ if ((count < 5) || (count > READ_WRITE_BUFFER_SIZE)) {
DEBUGP(2, dev, "<- cm4040_write buffersize=%Zd < 5\n", count);
return -EIO;
}
-
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