[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 <dan...@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