[PATCH bpf] bpftool: Don't crash on missing xlated program instructions

[PATCH bpf] bpftool: Don't crash on missing xlated program instructions

[Toke Høiland-Jørgensen]

Turns out the xlated program instructions can also be missing if
kptr_restrict sysctl is set. This means that the previous fix to check the
jited_prog_insns pointer was insufficient; add another check of the
xlated_prog_insns pointer as well.

Fixes: 5b79bcdf0362 ("bpftool: Don't crash on missing jited insns or ksyms")
Fixes: cae73f233923 ("bpftool: use bpf_program__get_prog_info_linear() in prog.c:do_dump()")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
 tools/bpf/bpftool/prog.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index a3521deca869..b352ab041160 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -536,7 +536,7 @@ prog_dump(struct bpf_prog_info *info, enum dump_mode mode,
 		buf = (unsigned char *)(info->jited_prog_insns);
 		member_len = info->jited_prog_len;
 	} else {	/* DUMP_XLATED */
-		if (info->xlated_prog_len == 0) {
+		if (info->xlated_prog_len == 0 || !info->xlated_prog_insns) {
 			p_err("error retrieving insn dump: kernel.kptr_restrict set?");
 			return -1;
 		}
-- 
2.25.0

Re: [PATCH bpf] bpftool: Don't crash on missing xlated program instructions

[Quentin Monnet]

2020-02-06 11:29 UTC+0100 ~ Toke Høiland-Jørgensen <toke@redhat.com>
> Turns out the xlated program instructions can also be missing if
> kptr_restrict sysctl is set. This means that the previous fix to check the
> jited_prog_insns pointer was insufficient; add another check of the
> xlated_prog_insns pointer as well.
> 
> Fixes: 5b79bcdf0362 ("bpftool: Don't crash on missing jited insns or ksyms")
> Fixes: cae73f233923 ("bpftool: use bpf_program__get_prog_info_linear() in prog.c:do_dump()")
> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
> ---
>   tools/bpf/bpftool/prog.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> index a3521deca869..b352ab041160 100644
> --- a/tools/bpf/bpftool/prog.c
> +++ b/tools/bpf/bpftool/prog.c
> @@ -536,7 +536,7 @@ prog_dump(struct bpf_prog_info *info, enum dump_mode mode,
>   		buf = (unsigned char *)(info->jited_prog_insns);
>   		member_len = info->jited_prog_len;
>   	} else {	/* DUMP_XLATED */
> -		if (info->xlated_prog_len == 0) {
> +		if (info->xlated_prog_len == 0 || !info->xlated_prog_insns) {
>   			p_err("error retrieving insn dump: kernel.kptr_restrict set?");
>   			return -1;
>   		}
> 

The fix looks good, thanks!

Reviewed-by: Quentin Monnet <quentin@isovalent.com>

Re: [PATCH bpf] bpftool: Don't crash on missing xlated program instructions

[Daniel Borkmann]

On 2/6/20 11:29 AM, Toke Høiland-Jørgensen wrote:
> Turns out the xlated program instructions can also be missing if
> kptr_restrict sysctl is set. This means that the previous fix to check the
> jited_prog_insns pointer was insufficient; add another check of the
> xlated_prog_insns pointer as well.
> 
> Fixes: 5b79bcdf0362 ("bpftool: Don't crash on missing jited insns or ksyms")
> Fixes: cae73f233923 ("bpftool: use bpf_program__get_prog_info_linear() in prog.c:do_dump()")
> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>

Applied, thanks!