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authorJohn Fastabend <john.fastabend@gmail.com>2018-02-05 10:17:54 -0800
committerDaniel Borkmann <daniel@iogearbox.net>2018-02-06 11:39:32 +0100
commit3d9e952697de89b53227f06d4241f275eb99cfc4 (patch)
tree07ee2d1dc8963140d2e718a8600112892c8add3f /kernel
parent1aa12bdf1bfb95db7e75bfecf0e39a65f4e8fbf8 (diff)
downloadlinux-3d9e952697de89b53227f06d4241f275eb99cfc4.tar.bz2
bpf: sockmap, fix leaking maps with attached but not detached progs
When a program is attached to a map we increment the program refcnt to ensure that the program is not removed while it is potentially being referenced from sockmap side. However, if this same program also references the map (this is a reasonably common pattern in my programs) then the verifier will also increment the maps refcnt from the verifier. This is to ensure the map doesn't get garbage collected while the program has a reference to it. So we are left in a state where the map holds the refcnt on the program stopping it from being removed and releasing the map refcnt. And vice versa the program holds a refcnt on the map stopping it from releasing the refcnt on the prog. All this is fine as long as users detach the program while the map fd is still around. But, if the user omits this detach command we are left with a dangling map we can no longer release. To resolve this when the map fd is released decrement the program references and remove any reference from the map to the program. This fixes the issue with possibly dangling map and creates a user side API constraint. That is, the map fd must be held open for programs to be attached to a map. Fixes: 174a79ff9515 ("bpf: sockmap with sk redirect support") Signed-off-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/sockmap.c19
1 files changed, 14 insertions, 5 deletions
diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index bd4a6d9c6709..48c33417d13c 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -620,11 +620,6 @@ static void sock_map_free(struct bpf_map *map)
}
rcu_read_unlock();
- if (stab->bpf_verdict)
- bpf_prog_put(stab->bpf_verdict);
- if (stab->bpf_parse)
- bpf_prog_put(stab->bpf_parse);
-
sock_map_remove_complete(stab);
}
@@ -900,6 +895,19 @@ static int sock_map_update_elem(struct bpf_map *map,
return err;
}
+static void sock_map_release(struct bpf_map *map, struct file *map_file)
+{
+ struct bpf_stab *stab = container_of(map, struct bpf_stab, map);
+ struct bpf_prog *orig;
+
+ orig = xchg(&stab->bpf_parse, NULL);
+ if (orig)
+ bpf_prog_put(orig);
+ orig = xchg(&stab->bpf_verdict, NULL);
+ if (orig)
+ bpf_prog_put(orig);
+}
+
const struct bpf_map_ops sock_map_ops = {
.map_alloc = sock_map_alloc,
.map_free = sock_map_free,
@@ -907,6 +915,7 @@ const struct bpf_map_ops sock_map_ops = {
.map_get_next_key = sock_map_get_next_key,
.map_update_elem = sock_map_update_elem,
.map_delete_elem = sock_map_delete_elem,
+ .map_release = sock_map_release,
};
BPF_CALL_4(bpf_sock_map_update, struct bpf_sock_ops_kern *, bpf_sock,