bpf: fix bug in eBPF verifier

while comparing for verifier state equivalency the comparison
was missing a check for uninitialized register.
Make sure it does so and add a testcase.

Fixes: f1bca824dabb ("bpf: add search pruning optimization to verifier")
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 13 insertions, 1 deletions

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 801f5f3b9307..9f81818f2941 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1409,7 +1409,8 @@ static bool states_equal(struct verifier_state *old, struct verifier_state *cur)
                 if (memcmp(&old->regs[i], &cur->regs[i],
                            sizeof(old->regs[0])) != 0) {
                         if (old->regs[i].type == NOT_INIT ||
-                            old->regs[i].type == UNKNOWN_VALUE)
+                            (old->regs[i].type == UNKNOWN_VALUE &&
+                             cur->regs[i].type != NOT_INIT))
                                 continue;
                         return false;
                 }
diff --git a/samples/bpf/test_verifier.c b/samples/bpf/test_verifier.c
index f44ef11f65a7..eb4bec0ad8af 100644
--- a/samples/bpf/test_verifier.c
+++ b/samples/bpf/test_verifier.c
@@ -209,6 +209,17 @@ static struct bpf_test tests[] = {
                 .result = REJECT,
         },
         {
+                "program doesn't init R0 before exit in all branches",
+                .insns = {
+                        BPF_JMP_IMM(BPF_JGE, BPF_REG_1, 0, 2),
+                        BPF_MOV64_IMM(BPF_REG_0, 1),
+                        BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 2),
+                        BPF_EXIT_INSN(),
+                },
+                .errstr = "R0 !read_ok",
+                .result = REJECT,
+        },
+        {
                 "stack out of bounds",
                 .insns = {
                         BPF_ST_MEM(BPF_DW, BPF_REG_10, 8, 0),