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SubjectRe: [PATCH] net: ipv4: current group_info should be put after using.
On Fri, Apr 11, 2014 at 01:37:08PM -0400, Wang, Xiaoming wrote:
> There is a memory leak in ping. Current group_info had been got in
> ping_init_sock and group_info->usage increased.
> But the usage hasn't decreased anywhere in ping.
> This will make this group_info never freed and cause memory leak.
>

Memory leak is only one of possible side-effects, thus I believe commit
message should be adjusted.

This is a typical refcount leak exploitable by unprivileged users, so
side effects can range from nothing through memory leaks and crashes to
possibly privilege escalation.

That said losing ' and cause memory leak' from your commit message
would be fine in my opinion.

See also a nit below.

> ---
> net/ipv4/ping.c | 11 ++++++++---
> 1 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
> index f4b19e5..2af7b1f 100644
> --- a/net/ipv4/ping.c
> +++ b/net/ipv4/ping.c
> @@ -255,23 +255,28 @@ int ping_init_sock(struct sock *sk)
> struct group_info *group_info = get_current_groups();
> int i, j, count = group_info->ngroups;
> kgid_t low, high;
> + int ret = 0;
>
> inet_get_ping_group_range_net(net, &low, &high);
> if (gid_lte(low, group) && gid_lte(group, high))
> - return 0;
> + goto out_release_group;
>

Since group_info is not even used here maybe it would be better to leave
return 0 as it is and call get_current_groups before the loop?

> for (i = 0; i < group_info->nblocks; i++) {
> int cp_count = min_t(int, NGROUPS_PER_BLOCK, count);
> for (j = 0; j < cp_count; j++) {
> kgid_t gid = group_info->blocks[i][j];
> if (gid_lte(low, gid) && gid_lte(gid, high))
> - return 0;
> + goto out_release_group;
> }
>
> count -= cp_count;
> }
>
> - return -EACCES;
> + ret = -EACCES;
> +
> +out_release_group:
> + put_group_info(group_info);
> + return ret;
> }
> EXPORT_SYMBOL_GPL(ping_init_sock);
>

--
Mateusz Guzik


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