On Tue, Nov 19, 2024 at 2:17 AM Anton Protopopov <aspsk@xxxxxxxxxxxxx> wrote:
>
> The bpf_remove_insns() function returns WARN_ON_ONCE(error), where
> error is a result of bpf_adj_branches(), and thus should be always 0
> However, if for any reason it is not 0, then it will be converted to
> boolean by WARN_ON_ONCE and returned to user space as 1, not an actual
> error value. Fix this by returning the original err after the WARN check.
>
> Signed-off-by: Anton Protopopov <aspsk@xxxxxxxxxxxxx>
> Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
> kernel/bpf/core.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 14d9288441f2..a15059918768 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -539,6 +539,8 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
>
> int bpf_remove_insns(struct bpf_prog *prog, u32 off, u32 cnt)
> {
> + int err;
> +
> /* Branch offsets can't overflow when program is shrinking, no need
> * to call bpf_adj_branches(..., true) here
> */
> @@ -546,7 +548,12 @@ int bpf_remove_insns(struct bpf_prog *prog, u32 off, u32 cnt)
> sizeof(struct bpf_insn) * (prog->len - off - cnt));
> prog->len -= cnt;
>
> - return WARN_ON_ONCE(bpf_adj_branches(prog, off, off + cnt, off, false));
> + err = bpf_adj_branches(prog, off, off + cnt, off, false);
> + WARN_ON_ONCE(err);
> + if (err)
> + return err;
> +
> + return 0;
That looks very odd. Just return err ?
