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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: c31a25e1db ("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 <dhowells@redhat.com>
Tested-by: syzbot+dd1339599f1840e4cc65@syzkaller.appspotmail.com
cc: Tom Herbert <tom@herbertland.com>
cc: Tom Herbert <tom@quantonium.net>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
Link: https://lore.kernel.org/r/20787.1686828722@warthog.procyon.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
David Howells 2023-06-15 12:32:02 +01:00 committed by Jakub Kicinski
parent 5a6f687360
commit 9f8d0dc0ec
1 changed files with 3 additions and 1 deletions
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4
net/kcm/kcmsock.c
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@ -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 */