| Message ID | 20180516214651.6664.62408.stgit@john-Precision-Tower-5810 |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | [bpf,1/2] bpf: sockmap update rollback on error can incorrectly dec prog refcnt | expand |
On Wed, May 16, 2018 at 02:46:51PM -0700, John Fastabend wrote: > If the user were to only attach one of the parse or verdict programs > then it is possible a subsequent sockmap update could incorrectly > decrement the refcnt on the program. This happens because in the > rollback logic, after an error, we have to decrement the program > reference count when its been incremented. However, we only increment > the program reference count if the user has both a verdict and a > parse program. The reason for this is because, at least at the > moment, both are required for any one to be meaningful. The problem > fixed here is in the rollback path we decrement the program refcnt > even if only one existing. But we never incremented the refcnt in > the first place creating an imbalance. > > This patch fixes the error path to handle this case. > > Fixes: 2f857d04601a ("bpf: sockmap, remove STRPARSER map_flags and add multi-map support") > Reported-by: Daniel Borkmann <daniel@iogearbox.net> > Signed-off-by: John Fastabend <john.fastabend@gmail.com> Acked-by: Martin KaFai Lau <kafai@fb.com>
diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c index 098eca5..f03aaa8 100644 --- a/kernel/bpf/sockmap.c +++ b/kernel/bpf/sockmap.c @@ -1717,10 +1717,10 @@ static int sock_map_ctx_update_elem(struct bpf_sock_ops_kern *skops, if (tx_msg) { tx_msg = bpf_prog_inc_not_zero(stab->bpf_tx_msg); if (IS_ERR(tx_msg)) { - if (verdict) - bpf_prog_put(verdict); - if (parse) + if (parse && verdict) { bpf_prog_put(parse); + bpf_prog_put(verdict); + } return PTR_ERR(tx_msg); } } @@ -1805,10 +1805,10 @@ static int sock_map_ctx_update_elem(struct bpf_sock_ops_kern *skops, out_free: smap_release_sock(psock, sock); out_progs: - if (verdict) - bpf_prog_put(verdict); - if (parse) + if (parse && verdict) { bpf_prog_put(parse); + bpf_prog_put(verdict); + } if (tx_msg) bpf_prog_put(tx_msg); write_unlock_bh(&sock->sk_callback_lock);
If the user were to only attach one of the parse or verdict programs then it is possible a subsequent sockmap update could incorrectly decrement the refcnt on the program. This happens because in the rollback logic, after an error, we have to decrement the program reference count when its been incremented. However, we only increment the program reference count if the user has both a verdict and a parse program. The reason for this is because, at least at the moment, both are required for any one to be meaningful. The problem fixed here is in the rollback path we decrement the program refcnt even if only one existing. But we never incremented the refcnt in the first place creating an imbalance. This patch fixes the error path to handle this case. Fixes: 2f857d04601a ("bpf: sockmap, remove STRPARSER map_flags and add multi-map support") Reported-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: John Fastabend <john.fastabend@gmail.com> --- kernel/bpf/sockmap.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)