Commits
Jiri Olsa committed 752bcf80f55
bpftool: Fix prog dump by tag
Lance reported an issue with bpftool not being able to
dump program if there are more programs loaded and you
want to dump any but the first program, like:
# bpftool prog
28: kprobe name trace_req_start tag 1dfc28ba8b3dd597 gpl
loaded_at 2019-01-18T17:02:40+1100 uid 0
xlated 112B jited 109B memlock 4096B map_ids 13
29: kprobe name trace_req_compl tag 5b6a5ecc6030a683 gpl
loaded_at 2019-01-18T17:02:40+1100 uid 0
xlated 928B jited 575B memlock 4096B map_ids 13,14
# bpftool prog dum jited tag 1dfc28ba8b3dd597
0: push %rbp
1: mov %rsp,%rbp
...
# bpftool prog dum jited tag 5b6a5ecc6030a683
Error: can't get prog info (29): Bad address
The problem is in the prog_fd_by_tag function not cleaning
the struct bpf_prog_info before another request, so the
previous program length is still in there and kernel assumes
it needs to dump the program, which fails because there's no
user pointer set.
Moving the struct bpf_prog_info declaration into the loop,
so it gets cleaned before each query.
Fixes: 71bb428fe2c1 ("tools: bpf: add bpftool")
Reported-by: Lance Digby <ldigby@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>