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Subject[70/74] irda: prevent integer underflow in IRLMP_ENUMDEVICES
2.6.32-longterm review patch.  If anyone has any objections, please let us know.

------------------
From: Dan Rosenberg <drosenberg@vsecurity.com>

commit fdac1e0697356ac212259f2147aa60c72e334861 upstream.

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>
Cc: Moritz Muehlenhoff <jmm@debian.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>


---
net/irda/af_irda.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
--- a/net/irda/af_irda.c
+++ b/net/irda/af_irda.c
@@ -2164,6 +2164,14 @@ static int irda_getsockopt(struct socket

switch (optname) {
case IRLMP_ENUMDEVICES:
+
+ /* Offset to first device entry */
+ offset = sizeof(struct irda_device_list) -
+ sizeof(struct irda_device_info);
+
+ if (len < offset)
+ return -EINVAL;
+
/* Ask lmp for the current discovery log */
discoveries = irlmp_get_discoveries(&list.len, self->mask.word,
self->nslots);
@@ -2173,15 +2181,9 @@ static int irda_getsockopt(struct socket
err = 0;

/* 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)
{



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