Revision 49054556289e8787501630b7c7a9d407da02e296 authored by Paolo Abeni on 29 September 2021, 09:59:17 UTC, committed by David S. Miller on 30 September 2021, 12:06:47 UTC
Syzkaller reported a false positive deadlock involving
the nl socket lock and the subflow socket lock:

MPTCP: kernel_bind error, err=-98
============================================
WARNING: possible recursive locking detected
5.15.0-rc1-syzkaller #0 Not tainted
--------------------------------------------
syz-executor998/6520 is trying to acquire lock:
ffff8880795718a0 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_close+0x267/0x7b0 net/mptcp/protocol.c:2738

but task is already holding lock:
ffff8880787c8c60 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1612 [inline]
ffff8880787c8c60 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_close+0x23/0x7b0 net/mptcp/protocol.c:2720

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(k-sk_lock-AF_INET);
  lock(k-sk_lock-AF_INET);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

3 locks held by syz-executor998/6520:
 #0: ffffffff8d176c50 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40 net/netlink/genetlink.c:802
 #1: ffffffff8d176d08 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:33 [inline]
 #1: ffffffff8d176d08 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x3e0/0x580 net/netlink/genetlink.c:790
 #2: ffff8880787c8c60 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1612 [inline]
 #2: ffff8880787c8c60 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_close+0x23/0x7b0 net/mptcp/protocol.c:2720

stack backtrace:
CPU: 1 PID: 6520 Comm: syz-executor998 Not tainted 5.15.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 print_deadlock_bug kernel/locking/lockdep.c:2944 [inline]
 check_deadlock kernel/locking/lockdep.c:2987 [inline]
 validate_chain kernel/locking/lockdep.c:3776 [inline]
 __lock_acquire.cold+0x149/0x3ab kernel/locking/lockdep.c:5015
 lock_acquire kernel/locking/lockdep.c:5625 [inline]
 lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590
 lock_sock_fast+0x36/0x100 net/core/sock.c:3229
 mptcp_close+0x267/0x7b0 net/mptcp/protocol.c:2738
 inet_release+0x12e/0x280 net/ipv4/af_inet.c:431
 __sock_release net/socket.c:649 [inline]
 sock_release+0x87/0x1b0 net/socket.c:677
 mptcp_pm_nl_create_listen_socket+0x238/0x2c0 net/mptcp/pm_netlink.c:900
 mptcp_nl_cmd_add_addr+0x359/0x930 net/mptcp/pm_netlink.c:1170
 genl_family_rcv_msg_doit+0x228/0x320 net/netlink/genetlink.c:731
 genl_family_rcv_msg net/netlink/genetlink.c:775 [inline]
 genl_rcv_msg+0x328/0x580 net/netlink/genetlink.c:792
 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2504
 genl_rcv+0x24/0x40 net/netlink/genetlink.c:803
 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340
 netlink_sendmsg+0x86d/0xdb0 net/netlink/af_netlink.c:1929
 sock_sendmsg_nosec net/socket.c:704 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:724
 sock_no_sendpage+0x101/0x150 net/core/sock.c:2980
 kernel_sendpage.part.0+0x1a0/0x340 net/socket.c:3504
 kernel_sendpage net/socket.c:3501 [inline]
 sock_sendpage+0xe5/0x140 net/socket.c:1003
 pipe_to_sendpage+0x2ad/0x380 fs/splice.c:364
 splice_from_pipe_feed fs/splice.c:418 [inline]
 __splice_from_pipe+0x43e/0x8a0 fs/splice.c:562
 splice_from_pipe fs/splice.c:597 [inline]
 generic_splice_sendpage+0xd4/0x140 fs/splice.c:746
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x110/0x180 fs/splice.c:936
 splice_direct_to_actor+0x34b/0x8c0 fs/splice.c:891
 do_splice_direct+0x1b3/0x280 fs/splice.c:979
 do_sendfile+0xae9/0x1240 fs/read_write.c:1249
 __do_sys_sendfile64 fs/read_write.c:1314 [inline]
 __se_sys_sendfile64 fs/read_write.c:1300 [inline]
 __x64_sys_sendfile64+0x1cc/0x210 fs/read_write.c:1300
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f215cb69969
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 14 00 00 90 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 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc96bb3868 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f215cbad072 RCX: 00007f215cb69969
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000005
RBP: 0000000000000000 R08: 00007ffc96bb3a08 R09: 00007ffc96bb3a08
R10: 0000000100000002 R11: 0000000000000246 R12: 00007ffc96bb387c
R13: 431bde82d7b634db R14: 0000000000000000 R15: 0000000000000000

the problem originates from uncorrect lock annotation in the mptcp
code and is only visible since commit 2dcb96bacce3 ("net: core: Correct
the sock::sk_lock.owned lockdep annotations"), but is present since
the port-based endpoint support initial implementation.

This patch addresses the issue introducing a nested variant of
lock_sock_fast() and using it in the relevant code path.

Fixes: 1729cf186d8a ("mptcp: create the listening socket for new port")
Fixes: 2dcb96bacce3 ("net: core: Correct the sock::sk_lock.owned lockdep annotations")
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Reported-and-tested-by: syzbot+1dd53f7a89b299d59eaf@syzkaller.appspotmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 parent d88fd1b
Raw File
earlycpio.c
// SPDX-License-Identifier: GPL-2.0-only
/* ----------------------------------------------------------------------- *
 *
 *   Copyright 2012 Intel Corporation; author H. Peter Anvin
 *
 * ----------------------------------------------------------------------- */

/*
 * earlycpio.c
 *
 * Find a specific cpio member; must precede any compressed content.
 * This is used to locate data items in the initramfs used by the
 * kernel itself during early boot (before the main initramfs is
 * decompressed.)  It is the responsibility of the initramfs creator
 * to ensure that these items are uncompressed at the head of the
 * blob.  Depending on the boot loader or package tool that may be a
 * separate file or part of the same file.
 */

#include <linux/earlycpio.h>
#include <linux/kernel.h>
#include <linux/string.h>

enum cpio_fields {
	C_MAGIC,
	C_INO,
	C_MODE,
	C_UID,
	C_GID,
	C_NLINK,
	C_MTIME,
	C_FILESIZE,
	C_MAJ,
	C_MIN,
	C_RMAJ,
	C_RMIN,
	C_NAMESIZE,
	C_CHKSUM,
	C_NFIELDS
};

/**
 * find_cpio_data - Search for files in an uncompressed cpio
 * @path:       The directory to search for, including a slash at the end
 * @data:       Pointer to the cpio archive or a header inside
 * @len:        Remaining length of the cpio based on data pointer
 * @nextoff:    When a matching file is found, this is the offset from the
 *              beginning of the cpio to the beginning of the next file, not the
 *              matching file itself. It can be used to iterate through the cpio
 *              to find all files inside of a directory path.
 *
 * Return:      &struct cpio_data containing the address, length and
 *              filename (with the directory path cut off) of the found file.
 *              If you search for a filename and not for files in a directory,
 *              pass the absolute path of the filename in the cpio and make sure
 *              the match returned an empty filename string.
 */

struct cpio_data find_cpio_data(const char *path, void *data,
				size_t len,  long *nextoff)
{
	const size_t cpio_header_len = 8*C_NFIELDS - 2;
	struct cpio_data cd = { NULL, 0, "" };
	const char *p, *dptr, *nptr;
	unsigned int ch[C_NFIELDS], *chp, v;
	unsigned char c, x;
	size_t mypathsize = strlen(path);
	int i, j;

	p = data;

	while (len > cpio_header_len) {
		if (!*p) {
			/* All cpio headers need to be 4-byte aligned */
			p += 4;
			len -= 4;
			continue;
		}

		j = 6;		/* The magic field is only 6 characters */
		chp = ch;
		for (i = C_NFIELDS; i; i--) {
			v = 0;
			while (j--) {
				v <<= 4;
				c = *p++;

				x = c - '0';
				if (x < 10) {
					v += x;
					continue;
				}

				x = (c | 0x20) - 'a';
				if (x < 6) {
					v += x + 10;
					continue;
				}

				goto quit; /* Invalid hexadecimal */
			}
			*chp++ = v;
			j = 8;	/* All other fields are 8 characters */
		}

		if ((ch[C_MAGIC] - 0x070701) > 1)
			goto quit; /* Invalid magic */

		len -= cpio_header_len;

		dptr = PTR_ALIGN(p + ch[C_NAMESIZE], 4);
		nptr = PTR_ALIGN(dptr + ch[C_FILESIZE], 4);

		if (nptr > p + len || dptr < p || nptr < dptr)
			goto quit; /* Buffer overrun */

		if ((ch[C_MODE] & 0170000) == 0100000 &&
		    ch[C_NAMESIZE] >= mypathsize &&
		    !memcmp(p, path, mypathsize)) {

			if (nextoff)
				*nextoff = (long)nptr - (long)data;

			if (ch[C_NAMESIZE] - mypathsize >= MAX_CPIO_FILE_NAME) {
				pr_warn(
				"File %s exceeding MAX_CPIO_FILE_NAME [%d]\n",
				p, MAX_CPIO_FILE_NAME);
			}
			strlcpy(cd.name, p + mypathsize, MAX_CPIO_FILE_NAME);

			cd.data = (void *)dptr;
			cd.size = ch[C_FILESIZE];
			return cd; /* Found it! */
		}
		len -= (nptr - p);
		p = nptr;
	}

quit:
	return cd;
}
back to top