• Liu Jian's avatar
    bpf, sockmap: Fix an infinite loop error when len is 0 in tcp_bpf_recvmsg_parser() · d900f3d2
    Liu Jian authored
    When the buffer length of the recvmsg system call is 0, we got the
    flollowing soft lockup problem:
    
    watchdog: BUG: soft lockup - CPU#3 stuck for 27s! [a.out:6149]
    CPU: 3 PID: 6149 Comm: a.out Kdump: loaded Not tainted 6.2.0+ #30
    Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014
    RIP: 0010:remove_wait_queue+0xb/0xc0
    Code: 5e 41 5f c3 cc cc cc cc 0f 1f 80 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 41 57 <41> 56 41 55 41 54 55 48 89 fd 53 48 89 f3 4c 8d 6b 18 4c 8d 73 20
    RSP: 0018:ffff88811b5978b8 EFLAGS: 00000246
    RAX: 0000000000000000 RBX: ffff88811a7d3780 RCX: ffffffffb7a4d768
    RDX: dffffc0000000000 RSI: ffff88811b597908 RDI: ffff888115408040
    RBP: 1ffff110236b2f1b R08: 0000000000000000 R09: ffff88811a7d37e7
    R10: ffffed10234fa6fc R11: 0000000000000001 R12: ffff88811179b800
    R13: 0000000000000001 R14: ffff88811a7d38a8 R15: ffff88811a7d37e0
    FS:  00007f6fb5398740(0000) GS:ffff888237180000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 0000000020000000 CR3: 000000010b6ba002 CR4: 0000000000370ee0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
     <TASK>
     tcp_msg_wait_data+0x279/0x2f0
     tcp_bpf_recvmsg_parser+0x3c6/0x490
     inet_recvmsg+0x280/0x290
     sock_recvmsg+0xfc/0x120
     ____sys_recvmsg+0x160/0x3d0
     ___sys_recvmsg+0xf0/0x180
     __sys_recvmsg+0xea/0x1a0
     do_syscall_64+0x3f/0x90
     entry_SYSCALL_64_after_hwframe+0x72/0xdc
    
    The logic in tcp_bpf_recvmsg_parser is as follows:
    
    msg_bytes_ready:
    	copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
    	if (!copied) {
    		wait data;
    		goto msg_bytes_ready;
    	}
    
    In this case, "copied" always is 0, the infinite loop occurs.
    
    According to the Linux system call man page, 0 should be returned in this
    case. Therefore, in tcp_bpf_recvmsg_parser(), if the length is 0, directly
    return. Also modify several other functions with the same problem.
    
    Fixes: 1f5be6b3 ("udp: Implement udp_bpf_recvmsg() for sockmap")
    Fixes: 9825d866 ("af_unix: Implement unix_dgram_bpf_recvmsg()")
    Fixes: c5d2177a ("bpf, sockmap: Fix race in ingress receive verdict with redirect to self")
    Fixes: 604326b4 ("bpf, sockmap: convert to generic sk_msg interface")
    Signed-off-by: default avatarLiu Jian <liujian56@huawei.com>
    Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
    Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
    Cc: Jakub Sitnicki <jakub@cloudflare.com>
    Link: https://lore.kernel.org/bpf/20230303080946.1146638-1-liujian56@huawei.com
    d900f3d2
unix_bpf.c 4.63 KB