From 9f8d0dc0ec4a4b5b78c0be83238c4511ff5f1ae0 Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 15 Jun 2023 12:32:02 +0100 Subject: [PATCH] kcm: Fix unnecessary psock unreservation. kcm_write_msgs() calls unreserve_psock() to release its hold on the underlying TCP socket if it has run out of things to transmit, but if we have nothing in the write queue on entry (e.g. because someone did a zero-length sendmsg), we don't actually go into the transmission loop and as a consequence don't call reserve_psock(). Fix this by skipping the call to unreserve_psock() if we didn't reserve a psock. Fixes: c31a25e1db48 ("kcm: Send multiple frags in one sendmsg()") Reported-by: syzbot+dd1339599f1840e4cc65@syzkaller.appspotmail.com Link: https://lore.kernel.org/r/000000000000a61ffe05fe0c3d08@google.com/ Signed-off-by: David Howells Tested-by: syzbot+dd1339599f1840e4cc65@syzkaller.appspotmail.com cc: Tom Herbert cc: Tom Herbert cc: Jens Axboe cc: Matthew Wilcox Link: https://lore.kernel.org/r/20787.1686828722@warthog.procyon.org.uk Signed-off-by: Jakub Kicinski --- net/kcm/kcmsock.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c index d75d775e9462..d0537c1c8cd7 100644 --- a/net/kcm/kcmsock.c +++ b/net/kcm/kcmsock.c @@ -661,6 +661,7 @@ retry: kcm_abort_tx_psock(psock, ret ? -ret : EPIPE, true); unreserve_psock(kcm); + psock = NULL; txm->started_tx = false; kcm_report_tx_retry(kcm); @@ -696,7 +697,8 @@ out: if (!head) { /* Done with all queued messages. */ WARN_ON(!skb_queue_empty(&sk->sk_write_queue)); - unreserve_psock(kcm); + if (psock) + unreserve_psock(kcm); } /* Check if write space is available */ -- 2.39.5