[PATCH 5.19 014/717] io_uring/af_unix: defer registered files gc to io_uring release

Greg Kroah-Hartman
2022-10-22T07:34:48Z

From: Pavel Begunkov <asml.silence@gmail.com>

commit 0091bfc81741b8d3aeb3b7ab8636f911b2de6e80 upstream.

Instead of putting io_uring's registered files in unix_gc() we want it
to be done by io_uring itself. The trick here is to consider io_uring
registered files for cycle detection but not actually putting them down.
Because io_uring can't register other ring instances, this will remove
all refs to the ring file triggering the ->release path and clean up
with io_ring_ctx_free().

Cc: stable@vger.kernel.org
Fixes: 6b06314c47e1 ("io_uring: add file set registration")
Reported-and-tested-by: David Bouman <dbouman03@gmail.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
[axboe: add kerneldoc comment to skb, fold in skb leak fix]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/skbuff.h | 2 ++
io_uring/io_uring.c | 1 +
net/unix/garbage.c | 20 ++++++++++++++++++++
3 files changed, 23 insertions(+)

--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -965,6 +965,7 @@ typedef unsigned char *sk_buff_data_t;
* @csum_level: indicates the number of consecutive checksums found in
* the packet minus one that have been verified as
* CHECKSUM_UNNECESSARY (max 3)
+ * @scm_io_uring: SKB holds io_uring registered files
* @dst_pending_confirm: need to confirm neighbour
* @decrypted: Decrypted SKB
* @slow_gro: state present at GRO time, slower prepare step required
@@ -1144,6 +1145,7 @@ struct sk_buff {
#endif
__u8 slow_gro:1;
__u8 csum_not_inet:1;
+ __u8 scm_io_uring:1;

#ifdef CONFIG_NET_SCHED
__u16 tc_index; /* traffic control index */
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -9484,6 +9484,7 @@ static int io_scm_file_account(struct io

UNIXCB(skb).fp = fpl;
skb->sk = sk;
+ skb->scm_io_uring = 1;
skb->destructor = unix_destruct_scm;
refcount_add(skb->truesize, &sk->sk_wmem_alloc);
}
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -204,6 +204,7 @@ void wait_for_unix_gc(void)
/* The external entry point: unix_gc() */
void unix_gc(void)
{
+ struct sk_buff *next_skb, *skb;
struct unix_sock *u;
struct unix_sock *next;
struct sk_buff_head hitlist;
@@ -297,11 +298,30 @@ void unix_gc(void)

spin_unlock(&unix_gc_lock);

+ /* We need io_uring to clean its registered files, ignore all io_uring
+ * originated skbs. It's fine as io_uring doesn't keep references to
+ * other io_uring instances and so killing all other files in the cycle
+ * will put all io_uring references forcing it to go through normal
+ * release.path eventually putting registered files.
+ */
+ skb_queue_walk_safe(&hitlist, skb, next_skb) {
+ if (skb->scm_io_uring) {
+ __skb_unlink(skb, &hitlist);
+ skb_queue_tail(&skb->sk->sk_receive_queue, skb);
+ }
+ }
+
/* Here we are. Hitlist is filled. Die. */
__skb_queue_purge(&hitlist);

spin_lock(&unix_gc_lock);

+ /* There could be io_uring registered files, just push them back to
+ * the inflight list
+ */
+ list_for_each_entry_safe(u, next, &gc_candidates, link)
+ list_move_tail(&u->link, &gc_inflight_list);
+
/* All candidates should have been detached by now. */
BUG_ON(!list_empty(&gc_candidates));