[PATCH iproute2 master] bpf: test for valid type in bpf_get_work_dir

[PATCH iproute2 master] bpf: test for valid type in bpf_get_work_dir

[Daniel Borkmann]

Jan-Erik reported an assertion in bpf_prog_to_subdir() failed where
type was BPF_PROG_TYPE_UNSPEC, which is only used in bpf_init_env()
to auto-mount and cache the bpf fs mount point.

Therefore, make sure when bpf_init_env() is called multiple times
(f.e. eBPF classifier with eBPF action attached) and bpf_mnt_cached
is set already that the type is also valid. In bpf_init_env(), we're
only interested in the mount point and not a type-specific subdir.

Fixes: e42256699cac ("bpf: make tc's bpf loader generic and move into lib")
Reported-by: Jan-Erik Rediger <janerik@rediger.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
 lib/bpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/bpf.c b/lib/bpf.c
index 211c3d1..04ee1ab 100644
--- a/lib/bpf.c
+++ b/lib/bpf.c
@@ -596,7 +596,7 @@ static const char *bpf_get_work_dir(enum bpf_prog_type type)
 	if (bpf_mnt_cached) {
 		const char *out = mnt;
 
-		if (out) {
+		if (out && type) {
 			snprintf(bpf_tmp, sizeof(bpf_tmp), "%s%s/",
 				 out, bpf_prog_to_subdir(type));
 			out = bpf_tmp;
-- 
1.9.3

Re: [PATCH iproute2 master] bpf: test for valid type in bpf_get_work_dir

[Stephen Hemminger]

On Mon,  6 Mar 2017 13:06:00 +0100
Daniel Borkmann <daniel@iogearbox.net> wrote:

> Jan-Erik reported an assertion in bpf_prog_to_subdir() failed where
> type was BPF_PROG_TYPE_UNSPEC, which is only used in bpf_init_env()
> to auto-mount and cache the bpf fs mount point.
> 
> Therefore, make sure when bpf_init_env() is called multiple times
> (f.e. eBPF classifier with eBPF action attached) and bpf_mnt_cached
> is set already that the type is also valid. In bpf_init_env(), we're
> only interested in the mount point and not a type-specific subdir.
> 
> Fixes: e42256699cac ("bpf: make tc's bpf loader generic and move into lib")
> Reported-by: Jan-Erik Rediger <janerik@rediger.net>
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Applied