bpf, offload: Replace bitwise AND by logical AND in bpf_prog_offload_info_fill

This if guards whether user-space wants a copy of the offload-jited
bytecode and whether this bytecode exists. By erroneously doing a bitwise
AND instead of a logical AND on user- and kernel-space buffer-size can lead
to no data being copied to user-space especially when user-space size is a
power of two and bigger then the kernel-space buffer.

Fixes: fcfb126defda ("bpf: add new jited info fields in bpf_dev_offload and bpf_prog_info")
Signed-off-by: Johannes Krude <johannes@krude.de>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/bpf/20200212193227.GA3769@phlox.h.transitiv.net

diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
index 2c5dc65..bd09290 100644 (file)
--- a/kernel/bpf/offload.c
+++ b/kernel/bpf/offload.c
@@ -321,7 +321,7 @@ int bpf_prog_offload_info_fill(struct bpf_prog_info *info,
 
        ulen = info->jited_prog_len;
        info->jited_prog_len = aux->offload->jited_len;
-       if (info->jited_prog_len & ulen) {
+       if (info->jited_prog_len && ulen) {
                uinsns = u64_to_user_ptr(info->jited_prog_insns);
                ulen = min_t(u32, info->jited_prog_len, ulen);
                if (copy_to_user(uinsns, aux->offload->jited_image, ulen)) {