[PATCH net] bpf: fix bpf_prog_get_info_by_fd to dump correct xlated_prog_len

[PATCH net] bpf: fix bpf_prog_get_info_by_fd to dump correct xlated_prog_len

[Daniel Borkmann]

bpf_prog_size(prog->len) is not the correct length we want to dump
back to user space. The code in bpf_prog_get_info_by_fd() uses this
to copy prog->insnsi to user space, but bpf_prog_size(prog->len) also
includes the size of struct bpf_prog itself plus program instructions
and is usually used either in context of accounting or for bpf_prog_alloc()
et al, thus we copy out of bounds in bpf_prog_get_info_by_fd()
potentially. Use the correct bpf_prog_insn_size() instead.

Fixes: 1e2709769086 ("bpf: Add BPF_OBJ_GET_INFO_BY_FD")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
 kernel/bpf/syscall.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 84bb399..6c772ad 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1312,7 +1312,7 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog,
 	}
 
 	ulen = info.xlated_prog_len;
-	info.xlated_prog_len = bpf_prog_size(prog->len);
+	info.xlated_prog_len = bpf_prog_insn_size(prog);
 	if (info.xlated_prog_len && ulen) {
 		uinsns = u64_to_user_ptr(info.xlated_prog_insns);
 		ulen = min_t(u32, info.xlated_prog_len, ulen);
-- 
1.9.3

Re: [PATCH net] bpf: fix bpf_prog_get_info_by_fd to dump correct xlated_prog_len

[Martin KaFai Lau]

On Fri, Jul 28, 2017 at 11:05 PM, Daniel Borkmann <daniel@iogearbox.net> wrote:
> bpf_prog_size(prog->len) is not the correct length we want to dump
> back to user space. The code in bpf_prog_get_info_by_fd() uses this
> to copy prog->insnsi to user space, but bpf_prog_size(prog->len) also
> includes the size of struct bpf_prog itself plus program instructions
> and is usually used either in context of accounting or for bpf_prog_alloc()
> et al, thus we copy out of bounds in bpf_prog_get_info_by_fd()
> potentially. Use the correct bpf_prog_insn_size() instead.
Acked-by: Martin KaFai Lau <kafai@fb.com>

>
> Fixes: 1e2709769086 ("bpf: Add BPF_OBJ_GET_INFO_BY_FD")
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
> ---
>  kernel/bpf/syscall.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 84bb399..6c772ad 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -1312,7 +1312,7 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog,
>         }
>
>         ulen = info.xlated_prog_len;
> -       info.xlated_prog_len = bpf_prog_size(prog->len);
> +       info.xlated_prog_len = bpf_prog_insn_size(prog);
>         if (info.xlated_prog_len && ulen) {
>                 uinsns = u64_to_user_ptr(info.xlated_prog_insns);
>                 ulen = min_t(u32, info.xlated_prog_len, ulen);
> --
> 1.9.3
>

Re: [PATCH net] bpf: fix bpf_prog_get_info_by_fd to dump correct xlated_prog_len

[David Miller]

From: Daniel Borkmann <daniel@iogearbox.net>
Date: Fri, 28 Jul 2017 17:05:25 +0200

> bpf_prog_size(prog->len) is not the correct length we want to dump
> back to user space. The code in bpf_prog_get_info_by_fd() uses this
> to copy prog->insnsi to user space, but bpf_prog_size(prog->len) also
> includes the size of struct bpf_prog itself plus program instructions
> and is usually used either in context of accounting or for bpf_prog_alloc()
> et al, thus we copy out of bounds in bpf_prog_get_info_by_fd()
> potentially. Use the correct bpf_prog_insn_size() instead.
> 
> Fixes: 1e2709769086 ("bpf: Add BPF_OBJ_GET_INFO_BY_FD")
> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Applied, thanks Daniel.