Messages in this thread Patch in this message | | | Date | Mon, 11 Jan 2016 14:26:19 +0200 | From | Matti Vaittinen <> | Subject | [PATCH 1/1] net: netlink: Fix multicast group storage allocation for families with more than one groups |
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Hello,
I got an oops when developing a driver utilizing more than 32 multicast groups. After a little print adding I saw that part of the address of policy struct was overwritten. It seems to me that amount of longs needed to store the multicast addresses is calculated wrong for families with more than one multicast groups. Problem is easy to reproduce by:
1. generating a module which registers large amount of multicast groups. 2. Loading the module 3. Sending the netlink message which requests multicast groups for this family.
I believe step 3 may not be even needed if there is enough of the groups registered.
Patch created against just cloned net repository below.
Br. Matti Vaittinen
Multicast groups are stored in global buffer. Check for needed buffer size incorrectly compares buffer size to first id for family. This means that for families with more than one mcast id one may allocate too small buffer and end up writing rest of the groups to some unallocated memory. Fix the buffer size check to compare allocated space to last mcast id for the family.
Tested on ARM using kernel 3.14
Signed-off-by: Matti Vaittinen <matti.vaittinen@nokia.com> --- net/netlink/genetlink.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c index bc0e504..a992083 100644 --- a/net/netlink/genetlink.c +++ b/net/netlink/genetlink.c @@ -185,7 +185,7 @@ static int genl_allocate_reserve_groups(int n_groups, int *first_id) } } - if (id >= mc_groups_longs * BITS_PER_LONG) { + if (id + n_groups >= mc_groups_longs * BITS_PER_LONG) { unsigned long new_longs = mc_groups_longs + BITS_TO_LONGS(n_groups); size_t nlen = new_longs * sizeof(unsigned long); -- 2.1.0
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