From: Jiri Olsa jolsa@kernel.org
[ Upstream commit 752bcf80f5549c9901b2e8bc77b2138de55b1026 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- tools/bpf/bpftool/prog.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c index 0de024a6cc2be..bbba0d61570fe 100644 --- a/tools/bpf/bpftool/prog.c +++ b/tools/bpf/bpftool/prog.c @@ -109,13 +109,14 @@ static void print_boot_time(__u64 nsecs, char *buf, unsigned int size)
static int prog_fd_by_tag(unsigned char *tag) { - struct bpf_prog_info info = {}; - __u32 len = sizeof(info); unsigned int id = 0; int err; int fd;
while (true) { + struct bpf_prog_info info = {}; + __u32 len = sizeof(info); + err = bpf_prog_get_next_id(id, &id); if (err) { p_err("%s", strerror(errno));