For a generic loop detection algorithm a graph node can be a loop
header for itself. However, state loop entries are computed for use in
is_state_visited(), where get_loop_entry(state)->branches is checked.
is_state_visited() also checks state->branches, thus the case when
state == state->loop_entry is not interesting for is_state_visited().
This change does not affect correctness, but simplifies
get_loop_entry() a bit and also simplifies change to
update_loop_entry() in patch 9.
Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
---
kernel/bpf/verifier.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index f750c8607470..02f60b8683b5 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1788,7 +1788,7 @@ static bool same_callsites(struct bpf_verifier_state *a, struct bpf_verifier_sta
* # Find outermost loop entry known for n
* def get_loop_entry(n):
* h = entries.get(n, None)
- * while h in entries and entries[h] != h:
+ * while h in entries:
* h = entries[h]
* return h
*
@@ -1827,7 +1827,7 @@ static struct bpf_verifier_state *get_loop_entry(struct bpf_verifier_env *env,
struct bpf_verifier_state *topmost = st->loop_entry, *old;
u32 steps = 0;
- while (topmost && topmost->loop_entry && topmost != topmost->loop_entry) {
+ while (topmost && topmost->loop_entry) {
if (steps++ > st->dfs_depth) {
WARN_ONCE(true, "verifier bug: infinite loop in get_loop_entry\n");
verbose(env, "verifier bug: infinite loop in get_loop_entry()\n");
@@ -1854,7 +1854,7 @@ static void update_loop_entry(struct bpf_verifier_state *cur, struct bpf_verifie
* hence 'cur' and 'hdr' are not in the same loop and there is
* no need to update cur->loop_entry.
*/
- if (hdr->branches && hdr->dfs_depth <= (cur->loop_entry ?: cur)->dfs_depth) {
+ if (hdr->branches && hdr->dfs_depth < (cur->loop_entry ?: cur)->dfs_depth) {
cur->loop_entry = hdr;
hdr->used_as_loop_entry = true;
}
--
2.48.1
