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pktgen: Limit how much data we copy onto the stack. 

A program that accidentally writes too much data to the pktgen file can overflow
the kernel stack and oops the machine. This is only triggerable by root, so
there's no security issue, but it's still an unfortunate bug.

printk() won't print more than 1024 bytes in a single call, anyways, so let's
just never copy more than that much data. We're on a fairly shallow stack, so
that should be safe even with CONFIG_4KSTACKS.

Signed-off-by: Nelson Elhage <nelhage@ksplice.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Nelson Elhage 2010-10-28 11:31:07 -07:00 committed by David S. Miller
parent 8acfe468b0
commit 448d7b5daf
1 changed files with 4 additions and 3 deletions
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7
net/core/pktgen.c
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@ -887,10 +887,11 @@ static ssize_t pktgen_if_write(struct file *file,
i += len;
if (debug) {
char tb[count + 1];
if (copy_from_user(tb, user_buffer, count))
size_t copy = min(count, 1023);
char tb[copy + 1];
if (copy_from_user(tb, user_buffer, copy))
return -EFAULT;
tb[count] = 0;
tb[copy] = 0;
printk(KERN_DEBUG "pktgen: %s,%lu buffer -:%s:-\n", name,
(unsigned long)count, tb);
}