• Kuniyuki Iwashima's avatar
    af_unix: Call scm_recv() only after scm_set_cred(). · 3f5f118b
    Kuniyuki Iwashima authored
    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_PASSCRED or SO_PASSPIDFD, scm_recv()
    would populate cmsg with garbage.
    
    Let's not call scm_recv() unless there is skb to receive.
    
    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-gfa0e21fa #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:
     <TASK>
     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
     </TASK>
    
    Fixes: 5e2ff670 ("scm: add SO_PASSPIDFD and SCM_PIDFD")
    Fixes: 1da177e4 ("Linux-2.6.12-rc2")
    Reported-by: default avatarsyzkaller <syzkaller@googlegroups.com>
    Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
    Reviewed-by: default avatarAlexander Mikhalitsyn <alexander@mihalicyn.com>
    Link: https://lore.kernel.org/r/20230622184351.91544-1-kuniyu@amazon.comSigned-off-by: default avatarJakub Kicinski <kuba@kernel.org>
    3f5f118b
af_unix.c 86.9 KB