net: bpf: reject invalid shifts

On ARM64, a BUG() is triggered in the eBPF JIT if a filter with a
constant shift that can't be encoded in the immediate field of the
UBFM/SBFM instructions is passed to the JIT.  Since these shifts
amounts, which are negative or >= regsize, are invalid, reject them in
the eBPF verifier and the classic BPF filter checker, for all
architectures.

Signed-off-by: Rabin Vincent <rabin@rab.in>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 0 deletions

diff --git a/net/core/filter.c b/net/core/filter.c
index 672eefbfbe99..37157c4c1a78 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -777,6 +777,11 @@ static int bpf_check_classic(const struct sock_filter *filter,
                         if (ftest->k == 0)
                                 return -EINVAL;
                         break;
+                case BPF_ALU | BPF_LSH | BPF_K:
+                case BPF_ALU | BPF_RSH | BPF_K:
+                        if (ftest->k >= 32)
+                                return -EINVAL;
+                        break;
                 case BPF_LD | BPF_MEM:
                 case BPF_LDX | BPF_MEM:
                 case BPF_ST: