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af_unix: fix struct pid leaks in OOB support 

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: 314001f0bf ("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>
This commit is contained in:
Eric Dumazet 2023-03-07 16:45:30 +00:00 committed by Jakub Kicinski
parent 8f14820801
commit 2aab4b9690
1 changed files with 8 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
net/unix/af_unix.c
View File

@ -2105,7 +2105,8 @@ 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;
@ -2116,6 +2117,11 @@ 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);
@ -2243,7 +2249,7 @@ 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++;