From 483bed2b0ddd12ec33fc9407e0c6e1088e77a97c Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Fri, 4 Nov 2016 00:01:19 +0100 Subject: [PATCH] bpf: fix htab map destruction when extra reserve is in use Commit a6ed3ea65d98 ("bpf: restore behavior of bpf_map_update_elem") added an extra per-cpu reserve to the hash table map to restore old behaviour from pre prealloc times. When non-prealloc is in use for a map, then problem is that once a hash table extra element has been linked into the hash-table, and the hash table is destroyed due to refcount dropping to zero, then htab_map_free() -> delete_all_elements() will walk the whole hash table and drop all elements via htab_elem_free(). The problem is that the element from the extra reserve is first fed to the wrong backend allocator and eventually freed twice. Fixes: a6ed3ea65d98 ("bpf: restore behavior of bpf_map_update_elem") Reported-by: Dmitry Vyukov Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- kernel/bpf/hashtab.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 570eeca7bdfa..ad1bc67aff1b 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -687,7 +687,8 @@ static void delete_all_elements(struct bpf_htab *htab) hlist_for_each_entry_safe(l, n, head, hash_node) { hlist_del_rcu(&l->hash_node); - htab_elem_free(htab, l); + if (l->state != HTAB_EXTRA_ELEM_USED) + htab_elem_free(htab, l); } } } -- 2.20.1