2011-02-14 10:54:55

by Vasily Kulikov

Subject: [PATCH] bridge: netfilter: fix information leak

Struct tmp is copied from userspace. It is not checked whether the "name"
field is NULL terminated. This may lead to buffer overflow and passing
contents of kernel stack as a module name to try_then_request_module() and,
consequently, to modprobe commandline. It would be seen by all userspace
processes.

Signed-off-by: Vasiliy Kulikov <[email protected]>
---
Compile tested.

net/bridge/netfilter/ebtables.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 5f1825d..1ea820b 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -1107,6 +1107,8 @@ static int do_replace(struct net *net, const void __user *user,
if (tmp.num_counters >= INT_MAX / sizeof(struct ebt_counter))
return -ENOMEM;

+ tmp.name[sizeof(tmp.name)-1] = 0;
+
countersize = COUNTER_OFFSET(tmp.nentries) * nr_cpu_ids;
newinfo = vmalloc(sizeof(*newinfo) + countersize);
if (!newinfo)
--
1.7.0.4

2011-02-14 15:50:39

by Patrick McHardy

Subject: Re: [PATCH] bridge: netfilter: fix information leak

Am 14.02.2011 11:54, schrieb Vasiliy Kulikov:
> Struct tmp is copied from userspace. It is not checked whether the "name"
> field is NULL terminated. This may lead to buffer overflow and passing
> contents of kernel stack as a module name to try_then_request_module() and,
> consequently, to modprobe commandline. It would be seen by all userspace
> processes.
>
> Signed-off-by: Vasiliy Kulikov <[email protected]>

Applied, thanks Vasiliy.