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irda: prevent integer underflow in IRLMP_ENUMDEVICES 

If the user-provided len is less than the expected offset, the
IRLMP_ENUMDEVICES getsockopt will do a copy_to_user() with a very large
size value.  While this isn't be a security issue on x86 because it will
get caught by the access_ok() check, it may leak large amounts of kernel
heap on other architectures.  In any event, this patch fixes it.

Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Dan Rosenberg 2010-12-22 13:58:27 +00:00 committed by David S. Miller
parent 1bde5ac493
commit fdac1e0697
1 changed files with 11 additions and 7 deletions
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18
net/irda/af_irda.c
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@ -2281,6 +2281,16 @@ static int irda_getsockopt(struct socket *sock, int level, int optname,
switch (optname) {
case IRLMP_ENUMDEVICES:
/* Offset to first device entry */
offset = sizeof(struct irda_device_list) -
sizeof(struct irda_device_info);
if (len < offset) {
err = -EINVAL;
goto out;
}
/* Ask lmp for the current discovery log */
discoveries = irlmp_get_discoveries(&list.len, self->mask.word,
self->nslots);
@ -2291,15 +2301,9 @@ static int irda_getsockopt(struct socket *sock, int level, int optname,
}
/* Write total list length back to client */
if (copy_to_user(optval, &list,
sizeof(struct irda_device_list) -
sizeof(struct irda_device_info)))
if (copy_to_user(optval, &list, offset))
err = -EFAULT;
/* Offset to first device entry */
offset = sizeof(struct irda_device_list) -
sizeof(struct irda_device_info);
/* Copy the list itself - watch for overflow */
if (list.len > 2048) {
err = -EINVAL;