bpf: speed up stacksafe check

Don't check the same stack liveness condition 8 times.
once is enough.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Edward Cree <ecree@solarflare.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 3 insertions, 1 deletions

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ba8e3134bbc2..0c6deb3f2be4 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5204,9 +5204,11 @@ static bool stacksafe(struct bpf_func_state *old,
         for (i = 0; i < old->allocated_stack; i++) {
                 spi = i / BPF_REG_SIZE;
 
-                if (!(old->stack[spi].spilled_ptr.live & REG_LIVE_READ))
+                if (!(old->stack[spi].spilled_ptr.live & REG_LIVE_READ)) {
+                        i += BPF_REG_SIZE - 1;
                         /* explored state didn't use this */
                         continue;
+                }
 
                 if (old->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_INVALID)
                         continue;