On Tue, Jul 25, 2023 at 08:11:58AM +0800, Lin Ma wrote: > Hello Leon, > > > > > On Sun, Jul 23, 2023 at 03:45:04PM +0800, Lin Ma wrote: > > > The nla_for_each_nested parsing in function > > > nldev_stat_set_counter_dynamic_doit() does not check the length of the > > > attribute. This can lead to an out-of-attribute read and allow a > > > malformed nlattr (e.g., length 0) to be viewed as a 4 byte integer. > > > > 1. Subject of this patch doesn't really match the change. > > My bad, a stupid mistake. I will fix that and prepare another patch. > > > 2. See my comment on your i40e patch. > > https://lore.kernel.org/netdev/20230724174435.GA11388@unreal/ > > > > Yeah I have seen that. Just as Jakub said, empty netlink attributes are valid > (they are viewed as flag). The point is that different attribute has different > length requirement. For this specific code, the RDMA_NLDEV_ATTR_STAT_HWCOUNTERS > attribute is a nested one whose inner attributes should be NLA_U32. But as you > can see in variable nldev_policy, the description does not use nested policy to > enfore that, which results in the bug discussed in my commit message. > > [RDMA_NLDEV_ATTR_STAT_HWCOUNTERS] = { .type = NLA_NESTED }, > > The elegant fix could be add the nested policy description to nldev_policy while > this is toublesome as no existing nla_attr has been given to this nested nlattr. > Hence, add the length check is the simplest solution and you can see such nla_len > check code all over the kernel. Right, and this is what bothers me. I would more than happy to change nla_for_each_nested() to be something like nla_for_each_nested_type(...., sizeof(u32)), which will skip empty lines, for code which can't have them. Thanks > > > Thanks > > Regards > Lin
