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socket: Add assertions around naked refcount decrements

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Sockets in a listen queue hold a reference to the parent listening
socket.  Several code paths release this reference manually when moving
a child socket out of the queue.

Replace comments about the expected post-decrement refcount value with
assertions.  Use refcount_load() instead of a plain load.  No functional
change intended.

MFC after:	1 week
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D31974
This commit is contained in:
Mark Johnston 2021-09-17 12:26:56 -04:00
parent dfcef87714
commit 6b288408ca
1 changed files with 16 additions and 10 deletions
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26
sys/kern/uipc_socket.c
View File

@ -1120,11 +1120,12 @@ void
sofree(struct socket *so)
{
struct protosw *pr = so->so_proto;
bool last __diagused;
SOCK_LOCK_ASSERT(so);
if ((so->so_state & SS_NOFDREF) == 0 || so->so_count != 0 ||
(so->so_state & SS_PROTOREF) || (so->so_qstate == SQ_COMP)) {
if ((so->so_state & (SS_NOFDREF | SS_PROTOREF)) != SS_NOFDREF ||
refcount_load(&so->so_count) != 0 || so->so_qstate == SQ_COMP) {
SOCK_UNLOCK(so);
return;
}
@ -1160,8 +1161,9 @@ sofree(struct socket *so)
__func__, so, sol));
TAILQ_REMOVE(&sol->sol_incomp, so, so_list);
sol->sol_incqlen--;
/* This is guarenteed not to be the last. */
refcount_release(&sol->so_count);
last = refcount_release(&sol->so_count);
KASSERT(!last, ("%s: released last reference for %p",
__func__, sol));
so->so_qstate = SQ_NONE;
so->so_listen = NULL;
} else
@ -1169,7 +1171,7 @@ sofree(struct socket *so)
("%s: so %p not on (in)comp with so_listen",
__func__, so));
sorele(sol);
KASSERT(so->so_count == 1,
KASSERT(refcount_load(&so->so_count) == 1,
("%s: so %p count %u", __func__, so, so->so_count));
so->so_count = 0;
}
@ -1225,6 +1227,7 @@ soclose(struct socket *so)
struct accept_queue lqueue;
struct socket *sp, *tsp;
int error = 0;
bool last __diagused;
KASSERT(!(so->so_state & SS_NOFDREF), ("soclose: SS_NOFDREF on enter"));
@ -1271,8 +1274,9 @@ soclose(struct socket *so)
sp->so_qstate = SQ_NONE;
sp->so_listen = NULL;
SOCK_UNLOCK(sp);
/* Guaranteed not to be the last. */
refcount_release(&so->so_count);
last = refcount_release(&so->so_count);
KASSERT(!last, ("%s: released last reference for %p",
__func__, so));
}
}
KASSERT((so->so_state & SS_NOFDREF) == 0, ("soclose: NOFDREF"));
@ -1284,7 +1288,7 @@ soclose(struct socket *so)
SOCK_UNLOCK(sp);
soabort(sp);
} else {
/* sp is now in sofree() */
/* See the handling of queued sockets in sofree(). */
SOCK_UNLOCK(sp);
}
}
@ -4010,6 +4014,7 @@ soisconnecting(struct socket *so)
void
soisconnected(struct socket *so)
{
bool last __diagused;
SOCK_LOCK(so);
so->so_state &= ~(SS_ISCONNECTING|SS_ISDISCONNECTING|SS_ISCONFIRMING);
@ -4042,8 +4047,9 @@ soisconnected(struct socket *so)
sorele(head);
return;
}
/* Not the last one, as so holds a ref. */
refcount_release(&head->so_count);
last = refcount_release(&head->so_count);
KASSERT(!last, ("%s: released last reference for %p",
__func__, head));
}
again:
if ((so->so_options & SO_ACCEPTFILTER) == 0) {