[34-longterm 236/247] irda: prevent integer underflow in IRLMP_ENUMDEVICES

Paul Gortmaker
2011-06-23T17:38:51Z

From: Dan Rosenberg <drosenberg@vsecurity.com>

-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.
-------------------

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>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
net/irda/af_irda.c | 16 +++++++++-------
1 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/net/irda/af_irda.c b/net/irda/af_irda.c
index 6fae047..e63c226 100644
--- a/net/irda/af_irda.c
+++ b/net/irda/af_irda.c
@@ -2278,6 +2278,14 @@ 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)
+ return -EINVAL;
+
/* Ask lmp for the current discovery log */
discoveries = irlmp_get_discoveries(&list.len, self->mask.word,
self->nslots);
@@ -2287,15 +2295,9 @@ static int __irda_getsockopt(struct socket *sock, int level, int optname,
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)
{
--
1.7.4.4