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SubjectRe: [PATCH] bpftool: Fix prog dump by tag
On Fri, 18 Jan 2019 13:58:17 +0100, Jiri Olsa wrote:
> 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.
>
> Reported-by: Lance Digby <ldigby@redhat.com>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>

Aw.

Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>

Thanks!

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