From 041933a1ec7b4173a8e638cae4f8e394331d7e54 Mon Sep 17 00:00:00 2001 From: Michal Luczaj Date: Fri, 17 May 2024 11:27:01 +0200 Subject: [PATCH 1/2] af_unix: Fix garbage collection of embryos carrying OOB with SCM_RIGHTS GC attempts to explicitly drop oob_skb's reference before purging the hit list. The problem is with embryos: kfree_skb(u->oob_skb) is never called on an embryo socket. The python script below [0] sends a listener's fd to its embryo as OOB data. While GC does collect the embryo's queue, it fails to drop the OOB skb's refcount. The skb which was in embryo's receive queue stays as unix_sk(sk)->oob_skb and keeps the listener's refcount [1]. Tell GC to dispose embryo's oob_skb. [0]: from array import array from socket import * addr = '\x00unix-oob' lis = socket(AF_UNIX, SOCK_STREAM) lis.bind(addr) lis.listen(1) s = socket(AF_UNIX, SOCK_STREAM) s.connect(addr) scm = (SOL_SOCKET, SCM_RIGHTS, array('i', [lis.fileno()])) s.sendmsg([b'x'], [scm], MSG_OOB) lis.close() [1] $ grep unix-oob /proc/net/unix $ ./unix-oob.py $ grep unix-oob /proc/net/unix 0000000000000000: 00000002 00000000 00000000 0001 02 0 @unix-oob 0000000000000000: 00000002 00000000 00010000 0001 01 6072 @unix-oob Fixes: 4090fa373f0e ("af_unix: Replace garbage collection algorithm.") Signed-off-by: Michal Luczaj Reviewed-by: Kuniyuki Iwashima Signed-off-by: Paolo Abeni --- net/unix/garbage.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff --git a/net/unix/garbage.c b/net/unix/garbage.c index 1f8b8cdfcdc8d..dfe94a90ece40 100644 --- a/net/unix/garbage.c +++ b/net/unix/garbage.c @@ -342,6 +342,18 @@ enum unix_recv_queue_lock_class { U_RECVQ_LOCK_EMBRYO, }; +static void unix_collect_queue(struct unix_sock *u, struct sk_buff_head *hitlist) +{ + skb_queue_splice_init(&u->sk.sk_receive_queue, hitlist); + +#if IS_ENABLED(CONFIG_AF_UNIX_OOB) + if (u->oob_skb) { + WARN_ON_ONCE(skb_unref(u->oob_skb)); + u->oob_skb = NULL; + } +#endif +} + static void unix_collect_skb(struct list_head *scc, struct sk_buff_head *hitlist) { struct unix_vertex *vertex; @@ -365,18 +377,11 @@ static void unix_collect_skb(struct list_head *scc, struct sk_buff_head *hitlist /* listener -> embryo order, the inversion never happens. */ spin_lock_nested(&embryo_queue->lock, U_RECVQ_LOCK_EMBRYO); - skb_queue_splice_init(embryo_queue, hitlist); + unix_collect_queue(unix_sk(skb->sk), hitlist); spin_unlock(&embryo_queue->lock); } } else { - skb_queue_splice_init(queue, hitlist); - -#if IS_ENABLED(CONFIG_AF_UNIX_OOB) - if (u->oob_skb) { - kfree_skb(u->oob_skb); - u->oob_skb = NULL; - } -#endif + unix_collect_queue(u, hitlist); } spin_unlock(&queue->lock); From e060e433e51246d970c5a8aa1c5ccd9ecc7ba4bf Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Fri, 17 May 2024 11:27:02 +0200 Subject: [PATCH 2/2] selftest: af_unix: Make SCM_RIGHTS into OOB data. scm_rights.c covers various test cases for inflight file descriptors and garbage collector for AF_UNIX sockets. Currently, SCM_RIGHTS messages are sent with 3-bytes string, and it's not good for MSG_OOB cases, as SCM_RIGTS cmsg goes with the first 2-bytes, which is non-OOB data. Let's send SCM_RIGHTS messages with 1-byte character to pack SCM_RIGHTS into OOB data. Signed-off-by: Kuniyuki Iwashima Signed-off-by: Michal Luczaj Signed-off-by: Paolo Abeni --- tools/testing/selftests/net/af_unix/scm_rights.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/net/af_unix/scm_rights.c b/tools/testing/selftests/net/af_unix/scm_rights.c index bab606c9f1eb0..2bfed46e0b19a 100644 --- a/tools/testing/selftests/net/af_unix/scm_rights.c +++ b/tools/testing/selftests/net/af_unix/scm_rights.c @@ -197,8 +197,8 @@ void __send_fd(struct __test_metadata *_metadata, const FIXTURE_VARIANT(scm_rights) *variant, int inflight, int receiver) { -#define MSG "nop" -#define MSGLEN 3 +#define MSG "x" +#define MSGLEN 1 struct { struct cmsghdr cmsghdr; int fd[2];