4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet edumazet@google.com
[ Upstream commit 797a22bd5298c2674d927893f46cadf619dad11d ]
syzbot was able to trigger another soft lockup [1]
I first thought it was the O(N^2) issue I mentioned in my prior fix (f657d22ee1f "net/x25: do not hold the cpu too long in x25_new_lci()"), but I eventually found that x25_bind() was not checking SOCK_ZAPPED state under socket lock protection.
This means that multiple threads can end up calling x25_insert_socket() for the same socket, and corrupt x25_list
[1] watchdog: BUG: soft lockup - CPU#0 stuck for 123s! [syz-executor.2:10492] Modules linked in: irq event stamp: 27515 hardirqs last enabled at (27514): [<ffffffff81006673>] trace_hardirqs_on_thunk+0x1a/0x1c hardirqs last disabled at (27515): [<ffffffff8100668f>] trace_hardirqs_off_thunk+0x1a/0x1c softirqs last enabled at (32): [<ffffffff8632ee73>] x25_get_neigh+0xa3/0xd0 net/x25/x25_link.c:336 softirqs last disabled at (34): [<ffffffff86324bc3>] x25_find_socket+0x23/0x140 net/x25/af_x25.c:341 CPU: 0 PID: 10492 Comm: syz-executor.2 Not tainted 5.0.0-rc7+ #88 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:__sanitizer_cov_trace_pc+0x4/0x50 kernel/kcov.c:97 Code: f4 ff ff ff e8 11 9f ea ff 48 c7 05 12 fb e5 08 00 00 00 00 e9 c8 e9 ff ff 90 90 90 90 90 90 90 90 90 90 90 90 90 55 48 89 e5 <48> 8b 75 08 65 48 8b 04 25 40 ee 01 00 65 8b 15 38 0c 92 7e 81 e2 RSP: 0018:ffff88806e94fc48 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13 RAX: 1ffff1100d84dac5 RBX: 0000000000000001 RCX: ffffc90006197000 RDX: 0000000000040000 RSI: ffffffff86324bf3 RDI: ffff88806c26d628 RBP: ffff88806e94fc48 R08: ffff88806c1c6500 R09: fffffbfff1282561 R10: fffffbfff1282560 R11: ffffffff89412b03 R12: ffff88806c26d628 R13: ffff888090455200 R14: dffffc0000000000 R15: 0000000000000000 FS: 00007f3a107e4700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f3a107e3db8 CR3: 00000000a5544000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __x25_find_socket net/x25/af_x25.c:327 [inline] x25_find_socket+0x7d/0x140 net/x25/af_x25.c:342 x25_new_lci net/x25/af_x25.c:355 [inline] x25_connect+0x380/0xde0 net/x25/af_x25.c:784 __sys_connect+0x266/0x330 net/socket.c:1662 __do_sys_connect net/socket.c:1673 [inline] __se_sys_connect net/socket.c:1670 [inline] __x64_sys_connect+0x73/0xb0 net/socket.c:1670 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x457e29 Code: ad b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f3a107e3c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457e29 RDX: 0000000000000012 RSI: 0000000020000200 RDI: 0000000000000005 RBP: 000000000073c040 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3a107e46d4 R13: 00000000004be362 R14: 00000000004ceb98 R15: 00000000ffffffff Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 10493 Comm: syz-executor.3 Not tainted 5.0.0-rc7+ #88 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:__read_once_size include/linux/compiler.h:193 [inline] RIP: 0010:queued_write_lock_slowpath+0x143/0x290 kernel/locking/qrwlock.c:86 Code: 4c 8d 2c 01 41 83 c7 03 41 0f b6 45 00 41 38 c7 7c 08 84 c0 0f 85 0c 01 00 00 8b 03 3d 00 01 00 00 74 1a f3 90 41 0f b6 55 00 <41> 38 d7 7c eb 84 d2 74 e7 48 89 df e8 cc aa 4e 00 eb dd be 04 00 RSP: 0018:ffff888085c47bd8 EFLAGS: 00000206 RAX: 0000000000000300 RBX: ffffffff89412b00 RCX: 1ffffffff1282560 RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffffffff89412b00 RBP: ffff888085c47c70 R08: 1ffffffff1282560 R09: fffffbfff1282561 R10: fffffbfff1282560 R11: ffffffff89412b03 R12: 00000000000000ff R13: fffffbfff1282560 R14: 1ffff11010b88f7d R15: 0000000000000003 FS: 00007fdd04086700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fdd04064db8 CR3: 0000000090be0000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: queued_write_lock include/asm-generic/qrwlock.h:104 [inline] do_raw_write_lock+0x1d6/0x290 kernel/locking/spinlock_debug.c:203 __raw_write_lock_bh include/linux/rwlock_api_smp.h:204 [inline] _raw_write_lock_bh+0x3b/0x50 kernel/locking/spinlock.c:312 x25_insert_socket+0x21/0xe0 net/x25/af_x25.c:267 x25_bind+0x273/0x340 net/x25/af_x25.c:703 __sys_bind+0x23f/0x290 net/socket.c:1481 __do_sys_bind net/socket.c:1492 [inline] __se_sys_bind net/socket.c:1490 [inline] __x64_sys_bind+0x73/0xb0 net/socket.c:1490 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x457e29
Fixes: 90c27297a9bf ("X.25 remove bkl in bind") Signed-off-by: Eric Dumazet edumazet@google.com Cc: andrew hendry andrew.hendry@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/x25/af_x25.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)
--- a/net/x25/af_x25.c +++ b/net/x25/af_x25.c @@ -678,8 +678,7 @@ static int x25_bind(struct socket *sock, struct sockaddr_x25 *addr = (struct sockaddr_x25 *)uaddr; int len, i, rc = 0;
- if (!sock_flag(sk, SOCK_ZAPPED) || - addr_len != sizeof(struct sockaddr_x25) || + if (addr_len != sizeof(struct sockaddr_x25) || addr->sx25_family != AF_X25) { rc = -EINVAL; goto out; @@ -694,9 +693,13 @@ static int x25_bind(struct socket *sock, }
lock_sock(sk); - x25_sk(sk)->source_addr = addr->sx25_addr; - x25_insert_socket(sk); - sock_reset_flag(sk, SOCK_ZAPPED); + if (sock_flag(sk, SOCK_ZAPPED)) { + x25_sk(sk)->source_addr = addr->sx25_addr; + x25_insert_socket(sk); + sock_reset_flag(sk, SOCK_ZAPPED); + } else { + rc = -EINVAL; + } release_sock(sk); SOCK_DEBUG(sk, "x25_bind: socket is bound\n"); out: