On Tue, Jun 21, 2022 at 10:13:44PM +0200, Toke Høiland-Jørgensen wrote:
> commit f858c2b2ca04fc7ead291821a793638ae120c11d upstream
>
> The verifier allows programs to call global functions as long as their
> argument types match, using BTF to check the function arguments. One of the
> allowed argument types to such global functions is PTR_TO_CTX; however the
> check for this fails on BPF_PROG_TYPE_EXT functions because the verifier
> uses the wrong type to fetch the vmlinux BTF ID for the program context
> type. This failure is seen when an XDP program is loaded using
> libxdp (which loads it as BPF_PROG_TYPE_EXT and attaches it to a global XDP
> type program).
>
> Fix the issue by passing in the target program type instead of the
> BPF_PROG_TYPE_EXT type to bpf_prog_get_ctx() when checking function
> argument compatibility.
>
> The first Fixes tag refers to the latest commit that touched the code in
> question, while the second one points to the code that first introduced
> the global function call verification.
>
> v2:
> - Use resolve_prog_type()
>
> Fixes: 3363bd0cfbb8 ("bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support")
> Fixes: 51c39bb1d5d1 ("bpf: Introduce function-by-function verification")
> Reported-by: Simon Sundberg <simon.sundberg@xxxxxx>
> Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
> Link: https://lore.kernel.org/r/20220606075253.28422-1-toke@xxxxxxxxxx
> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
> [ backport: open-code missing resolve_prog_type() helper, resolve context diff ]
> Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
All now queued up, thanks.
greg k-h
