From 603fc57ab70c306fa483ca66152223e861455e09 Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Tue, 27 Jun 2023 10:43:13 -0700 Subject: af_unix: Skip SCM_PIDFD if scm->pid is NULL. syzkaller hit a WARN_ON_ONCE(!scm->pid) in scm_pidfd_recv(). In unix_stream_read_generic(), if there is no skb in the queue, we could bail out the do-while loop without calling scm_set_cred(): 1. No skb in the queue 2. sk is non-blocking or shutdown(sk, RCV_SHUTDOWN) is called concurrently or peer calls close() If the socket is configured with SO_PASSPIDFD, scm_pidfd_recv() would populate cmsg with garbage emitting the warning. Let's skip SCM_PIDFD if scm->pid is NULL in scm_pidfd_recv(). Note another way would be skip calling scm_recv() in such cases, but this caused a regression resulting in commit 9d797ee2dce1 ("Revert "af_unix: Call scm_recv() only after scm_set_cred().""). WARNING: CPU: 1 PID: 3245 at include/net/scm.h:138 scm_pidfd_recv include/net/scm.h:138 [inline] WARNING: CPU: 1 PID: 3245 at include/net/scm.h:138 scm_recv.constprop.0+0x754/0x850 include/net/scm.h:177 Modules linked in: CPU: 1 PID: 3245 Comm: syz-executor.1 Not tainted 6.4.0-rc5-01219-gfa0e21fa4443 #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 RIP: 0010:scm_pidfd_recv include/net/scm.h:138 [inline] RIP: 0010:scm_recv.constprop.0+0x754/0x850 include/net/scm.h:177 Code: 67 fd e9 55 fd ff ff e8 4a 70 67 fd e9 7f fd ff ff e8 40 70 67 fd e9 3e fb ff ff e8 36 70 67 fd e9 02 fd ff ff e8 8c 3a 20 fd <0f> 0b e9 fe fb ff ff e8 50 70 67 fd e9 2e f9 ff ff e8 46 70 67 fd RSP: 0018:ffffc90009af7660 EFLAGS: 00010216 RAX: 00000000000000a1 RBX: ffff888041e58a80 RCX: ffffc90003852000 RDX: 0000000000040000 RSI: ffffffff842675b4 RDI: 0000000000000007 RBP: ffffc90009af7810 R08: 0000000000000007 R09: 0000000000000013 R10: 00000000000000f8 R11: 0000000000000001 R12: ffffc90009af7db0 R13: 0000000000000000 R14: ffff888041e58a88 R15: 1ffff9200135eecc FS: 00007f6b7113f640(0000) GS:ffff88806cf00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f6b7111de38 CR3: 0000000012a6e002 CR4: 0000000000770ee0 PKRU: 55555554 Call Trace: unix_stream_read_generic+0x5fe/0x1f50 net/unix/af_unix.c:2830 unix_stream_recvmsg+0x194/0x1c0 net/unix/af_unix.c:2880 sock_recvmsg_nosec net/socket.c:1019 [inline] sock_recvmsg+0x188/0x1d0 net/socket.c:1040 ____sys_recvmsg+0x210/0x610 net/socket.c:2712 ___sys_recvmsg+0xff/0x190 net/socket.c:2754 do_recvmmsg+0x25d/0x6c0 net/socket.c:2848 __sys_recvmmsg net/socket.c:2927 [inline] __do_sys_recvmmsg net/socket.c:2950 [inline] __se_sys_recvmmsg net/socket.c:2943 [inline] __x64_sys_recvmmsg+0x224/0x290 net/socket.c:2943 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3f/0x90 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x72/0xdc RIP: 0033:0x7f6b71da2e5d Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 73 9f 1b 00 f7 d8 64 89 01 48 RSP: 002b:00007f6b7113ecc8 EFLAGS: 00000246 ORIG_RAX: 000000000000012b RAX: ffffffffffffffda RBX: 00000000004bc050 RCX: 00007f6b71da2e5d RDX: 0000000000000007 RSI: 0000000020006600 RDI: 000000000000000b RBP: 00000000004bc050 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000120 R11: 0000000000000246 R12: 0000000000000000 R13: 000000000000006e R14: 00007f6b71e03530 R15: 0000000000000000 Fixes: 5e2ff6704a27 ("scm: add SO_PASSPIDFD and SCM_PIDFD") Reported-by: syzkaller Signed-off-by: Kuniyuki Iwashima Link: https://lore.kernel.org/r/20230627174314.67688-2-kuniyu@amazon.com Signed-off-by: Jakub Kicinski --- include/net/scm.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/include/net/scm.h b/include/net/scm.h index c67f765a165b..d456fc41b8bf 100644 --- a/include/net/scm.h +++ b/include/net/scm.h @@ -135,7 +135,9 @@ static __inline__ void scm_pidfd_recv(struct msghdr *msg, struct scm_cookie *scm return; } - WARN_ON_ONCE(!scm->pid); + if (!scm->pid) + return; + pidfd = pidfd_prepare(scm->pid, 0, &pidfd_file); if (put_cmsg(msg, SOL_SOCKET, SCM_PIDFD, sizeof(int), &pidfd)) { -- cgit From a9c49cc2f5b578c4ffa0ee135aa552d06dec0e82 Mon Sep 17 00:00:00 2001 From: Alexander Mikhalitsyn Date: Tue, 27 Jun 2023 10:43:14 -0700 Subject: net: scm: introduce and use scm_recv_unix helper Recently, our friends from bluetooth subsystem reported [1] that after commit 5e2ff6704a27 ("scm: add SO_PASSPIDFD and SCM_PIDFD") scm_recv() helper become unusable in kernel modules (because it uses unexported pidfd_prepare() API). We were aware of this issue and workarounded it in a hard way by commit 97154bcf4d1b ("af_unix: Kconfig: make CONFIG_UNIX bool"). But recently a new functionality was added in the scope of commit 817efd3cad74 ("Bluetooth: hci_sock: Forward credentials to monitor") and after that bluetooth can't be compiled as a kernel module. After some discussion in [1] we decided to split scm_recv() into two helpers, one won't support SCM_PIDFD (used for unix sockets), and another one will be completely the same as it was before commit 5e2ff6704a27 ("scm: add SO_PASSPIDFD and SCM_PIDFD"). Link: https://lore.kernel.org/lkml/CAJqdLrpFcga4n7wxBhsFqPQiN8PKFVr6U10fKcJ9W7AcZn+o6Q@mail.gmail.com/ [1] Fixes: 5e2ff6704a27 ("scm: add SO_PASSPIDFD and SCM_PIDFD") Signed-off-by: Alexander Mikhalitsyn Reviewed-by: Kuniyuki Iwashima Link: https://lore.kernel.org/r/20230627174314.67688-3-kuniyu@amazon.com Signed-off-by: Jakub Kicinski --- include/net/scm.h | 35 +++++++++++++++++++++++++---------- net/unix/af_unix.c | 4 ++-- 2 files changed, 27 insertions(+), 12 deletions(-) diff --git a/include/net/scm.h b/include/net/scm.h index d456fc41b8bf..c5bcdf65f55c 100644 --- a/include/net/scm.h +++ b/include/net/scm.h @@ -153,8 +153,8 @@ static __inline__ void scm_pidfd_recv(struct msghdr *msg, struct scm_cookie *scm fd_install(pidfd, pidfd_file); } -static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg, - struct scm_cookie *scm, int flags) +static inline bool __scm_recv_common(struct socket *sock, struct msghdr *msg, + struct scm_cookie *scm, int flags) { if (!msg->msg_control) { if (test_bit(SOCK_PASSCRED, &sock->flags) || @@ -162,7 +162,7 @@ static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg, scm->fp || scm_has_secdata(sock)) msg->msg_flags |= MSG_CTRUNC; scm_destroy(scm); - return; + return false; } if (test_bit(SOCK_PASSCRED, &sock->flags)) { @@ -175,19 +175,34 @@ static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg, put_cmsg(msg, SOL_SOCKET, SCM_CREDENTIALS, sizeof(ucreds), &ucreds); } - if (test_bit(SOCK_PASSPIDFD, &sock->flags)) - scm_pidfd_recv(msg, scm); + scm_passec(sock, msg, scm); - scm_destroy_cred(scm); + if (scm->fp) + scm_detach_fds(msg, scm); - scm_passec(sock, msg, scm); + return true; +} - if (!scm->fp) +static inline void scm_recv(struct socket *sock, struct msghdr *msg, + struct scm_cookie *scm, int flags) +{ + if (!__scm_recv_common(sock, msg, scm, flags)) return; - - scm_detach_fds(msg, scm); + + scm_destroy_cred(scm); } +static inline void scm_recv_unix(struct socket *sock, struct msghdr *msg, + struct scm_cookie *scm, int flags) +{ + if (!__scm_recv_common(sock, msg, scm, flags)) + return; + + if (test_bit(SOCK_PASSPIDFD, &sock->flags)) + scm_pidfd_recv(msg, scm); + + scm_destroy_cred(scm); +} #endif /* __LINUX_NET_SCM_H */ diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 3953daa2e1d0..123b35ddfd71 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -2427,7 +2427,7 @@ int __unix_dgram_recvmsg(struct sock *sk, struct msghdr *msg, size_t size, } err = (flags & MSG_TRUNC) ? skb->len - skip : size; - scm_recv(sock, msg, &scm, flags); + scm_recv_unix(sock, msg, &scm, flags); out_free: skb_free_datagram(sk, skb); @@ -2808,7 +2808,7 @@ unlock: mutex_unlock(&u->iolock); if (state->msg) - scm_recv(sock, state->msg, &scm, flags); + scm_recv_unix(sock, state->msg, &scm, flags); else scm_destroy(&scm); out: -- cgit