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: f1bca82 ("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>
penberg · Oct 22, 2014 · 32bf08a · 32bf08a
1 parent 78fd1d0
commit 32bf08a
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Showing 2 changed files with 13 additions and 1 deletion.
diff --git 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
@@ -208,6 +208,17 @@ static struct bpf_test tests[] = {
 		.errstr = "R0 !read_ok",
 		.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 = {