On 7/31/20 5:24 PM, Jiri Olsa wrote:

On Fri, Jul 31, 2020 at 03:51:45PM +0200, Daniel Borkmann wrote:

quoted

Hi David,

The following pull-request contains BPF updates for your *net* tree.

We've added 5 non-merge commits during the last 21 day(s) which contain
a total of 5 files changed, 126 insertions(+), 18 deletions(-).

The main changes are:

1) Fix a map element leak in HASH_OF_MAPS map type, from Andrii Nakryiko.

2) Fix a NULL pointer dereference in __btf_resolve_helper_id() when no
    btf_vmlinux is available, from Peilin Ye.

3) Init pos variable in __bpfilter_process_sockopt(), from Christoph Hellwig.

4) Fix a cgroup sockopt verifier test by specifying expected attach type,
    from Jean-Philippe Brucker.

Please consider pulling these changes from:

   git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git

Thanks a lot!

Note that when net gets merged into net-next later on, there is a small
merge conflict in kernel/bpf/btf.c between commit 5b801dfb7feb ("bpf: Fix
NULL pointer dereference in __btf_resolve_helper_id()") from the bpf tree
and commit 138b9a0511c7 ("bpf: Remove btf_id helpers resolving") from the
net-next tree.

Resolve as follows: remove the old hunk with the __btf_resolve_helper_id()
function. Change the btf_resolve_helper_id() so it actually tests for a
NULL btf_vmlinux and bails out:

int btf_resolve_helper_id(struct bpf_verifier_log *log,
                           const struct bpf_func_proto *fn, int arg)
{
         int id;

         if (fn->arg_type[arg] != ARG_PTR_TO_BTF_ID || !btf_vmlinux)
                 return -EINVAL;
         id = fn->btf_id[arg];
         if (!id || id > btf_vmlinux->nr_types)
                 return -EINVAL;
         return id;
}

Let me know if you run into any others issues (CC'ing Jiri Olsa so he's in
the loop with regards to merge conflict resolution).

we'll loose the bpf_log message, but I'm fine with that ;-) looks good

Checking again on the fix, even though it was only triggered by syzkaller
so far, I think it's also possible if users don't have BTF debug data set
in the Kconfig but use a helper that expects it, so agree, lets re-add the
log in this case:

int btf_resolve_helper_id(struct bpf_verifier_log *log,
                           const struct bpf_func_proto *fn, int arg)
{
         int id;

         if (fn->arg_type[arg] != ARG_PTR_TO_BTF_ID)
                 return -EINVAL;
         if (!btf_vmlinux) {
                 bpf_log(log, "btf_vmlinux doesn't exist\n");
                 return -EINVAL;
         }
         id = fn->btf_id[arg];
         if (!id || id > btf_vmlinux->nr_types)
                 return -EINVAL;
         return id;
}

Thanks,
Daniel