From: Eric Dumazet edumazet@google.com
[ Upstream commit 2aab4b96900272885bc157f8b236abf1cdc02e08 ]
syzbot reported struct pid leak [1].
Issue is that queue_oob() calls maybe_add_creds() which potentially holds a reference on a pid.
But skb->destructor is not set (either directly or by calling unix_scm_to_skb())
This means that subsequent kfree_skb() or consume_skb() would leak this reference.
In this fix, I chose to fully support scm even for the OOB message.
[1] BUG: memory leak unreferenced object 0xffff8881053e7f80 (size 128): comm "syz-executor242", pid 5066, jiffies 4294946079 (age 13.220s) hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<ffffffff812ae26a>] alloc_pid+0x6a/0x560 kernel/pid.c:180 [<ffffffff812718df>] copy_process+0x169f/0x26c0 kernel/fork.c:2285 [<ffffffff81272b37>] kernel_clone+0xf7/0x610 kernel/fork.c:2684 [<ffffffff812730cc>] __do_sys_clone+0x7c/0xb0 kernel/fork.c:2825 [<ffffffff849ad699>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [<ffffffff849ad699>] do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 [<ffffffff84a0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
Fixes: 314001f0bf92 ("af_unix: Add OOB support") Reported-by: syzbot+7699d9e5635c10253a27@syzkaller.appspotmail.com Signed-off-by: Eric Dumazet edumazet@google.com Cc: Rao Shoaib rao.shoaib@oracle.com Reviewed-by: Kuniyuki Iwashima kuniyu@amazon.com Link: https://lore.kernel.org/r/20230307164530.771896-1-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/unix/af_unix.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 32ddf8fe32c69..a96026dbdf94e 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1970,7 +1970,8 @@ static int unix_dgram_sendmsg(struct socket *sock, struct msghdr *msg, #define UNIX_SKB_FRAGS_SZ (PAGE_SIZE << get_order(32768))
#if IS_ENABLED(CONFIG_AF_UNIX_OOB) -static int queue_oob(struct socket *sock, struct msghdr *msg, struct sock *other) +static int queue_oob(struct socket *sock, struct msghdr *msg, struct sock *other, + struct scm_cookie *scm, bool fds_sent) { struct unix_sock *ousk = unix_sk(other); struct sk_buff *skb; @@ -1981,6 +1982,11 @@ static int queue_oob(struct socket *sock, struct msghdr *msg, struct sock *other if (!skb) return err;
+ err = unix_scm_to_skb(scm, skb, !fds_sent); + if (err < 0) { + kfree_skb(skb); + return err; + } skb_put(skb, 1); err = skb_copy_datagram_from_iter(skb, 0, &msg->msg_iter, 1);
@@ -2108,7 +2114,7 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg,
#if IS_ENABLED(CONFIG_AF_UNIX_OOB) if (msg->msg_flags & MSG_OOB) { - err = queue_oob(sock, msg, other); + err = queue_oob(sock, msg, other, &scm, fds_sent); if (err) goto out_err; sent++;