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bpf: Prevent double bpf_prog_put call from bpf_tracing_prog_attach 

The bpf_tracing_prog_attach error path calls bpf_prog_put
on prog, which causes refcount underflow when it's called
from link_create function.

  link_create
    prog = bpf_prog_get              <-- get
    ...
    tracing_bpf_link_attach(prog..
      bpf_tracing_prog_attach(prog..
        out_put_prog:
          bpf_prog_put(prog);        <-- put

    if (ret < 0)
      bpf_prog_put(prog);            <-- put

Removing bpf_prog_put call from bpf_tracing_prog_attach
and making sure its callers call it instead.

Fixes: 4a1e7c0c63 ("bpf: Support attaching freplace programs to multiple attach points")
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210111191650.1241578-1-jolsa@kernel.org
This commit is contained in:
Jiri Olsa 2021-01-11 20:16:50 +01:00 committed by Daniel Borkmann
parent f97844f9c5
commit 5541075a34
1 changed files with 4 additions and 2 deletions
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6
kernel/bpf/syscall.c
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@ -2712,7 +2712,6 @@ out_unlock:
out_put_prog:
if (tgt_prog_fd && tgt_prog)
bpf_prog_put(tgt_prog);
bpf_prog_put(prog);
return err;
}
@ -2825,7 +2824,10 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
tp_name = prog->aux->attach_func_name;
break;
}
return bpf_tracing_prog_attach(prog, 0, 0);
err = bpf_tracing_prog_attach(prog, 0, 0);
if (err >= 0)
return err;
goto out_put_prog;
case BPF_PROG_TYPE_RAW_TRACEPOINT:
case BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE:
if (strncpy_from_user(buf,