• Eric Dumazet's avatar
    llc: only change llc->dev when bind() succeeds · 2d327a79
    Eric Dumazet authored
    My latest patch, attempting to fix the refcount leak in a minimal
    way turned out to add a new bug.
    
    Whenever the bind operation fails before we attempt to grab
    a reference count on a device, we might release the device refcount
    of a prior successful bind() operation.
    
    syzbot was not happy about this [1].
    
    Note to stable teams:
    
    Make sure commit b37a4668 ("netdevice: add the case if dev is NULL")
    is already present in your trees.
    
    [1]
    general protection fault, probably for non-canonical address 0xdffffc0000000070: 0000 [#1] PREEMPT SMP KASAN
    KASAN: null-ptr-deref in range [0x0000000000000380-0x0000000000000387]
    CPU: 1 PID: 3590 Comm: syz-executor361 Tainted: G        W         5.17.0-syzkaller-04796-g169e7776 #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
    RIP: 0010:llc_ui_connect+0x400/0xcb0 net/llc/af_llc.c:500
    Code: 80 3c 02 00 0f 85 fc 07 00 00 4c 8b a5 38 05 00 00 48 b8 00 00 00 00 00 fc ff df 49 8d bc 24 80 03 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 a9 07 00 00 49 8b b4 24 80 03 00 00 4c 89 f2 48
    RSP: 0018:ffffc900038cfcc0 EFLAGS: 00010202
    RAX: dffffc0000000000 RBX: ffff8880756eb600 RCX: 0000000000000000
    RDX: 0000000000000070 RSI: ffffc900038cfe3e RDI: 0000000000000380
    RBP: ffff888015ee5000 R08: 0000000000000001 R09: ffff888015ee5535
    R10: ffffed1002bdcaa6 R11: 0000000000000000 R12: 0000000000000000
    R13: ffffc900038cfe37 R14: ffffc900038cfe38 R15: ffff888015ee5012
    FS:  0000555555acd300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 0000000020000280 CR3: 0000000077db6000 CR4: 00000000003506e0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
     <TASK>
     __sys_connect_file+0x155/0x1a0 net/socket.c:1900
     __sys_connect+0x161/0x190 net/socket.c:1917
     __do_sys_connect net/socket.c:1927 [inline]
     __se_sys_connect net/socket.c:1924 [inline]
     __x64_sys_connect+0x6f/0xb0 net/socket.c:1924
     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: 0033:0x7f016acb90b9
    Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 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:00007ffd417947f8 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
    RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f016acb90b9
    RDX: 0000000000000010 RSI: 0000000020000140 RDI: 0000000000000003
    RBP: 00007f016ac7d0a0 R08: 0000000000000000 R09: 0000000000000000
    R10: 0000000000000000 R11: 0000000000000246 R12: 00007f016ac7d130
    R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
     </TASK>
    Modules linked in:
    ---[ end trace 0000000000000000 ]---
    RIP: 0010:llc_ui_connect+0x400/0xcb0 net/llc/af_llc.c:500
    
    Fixes: 764f4eb6 ("llc: fix netdevice reference leaks in llc_ui_bind()")
    Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
    Reported-by: default avatarsyzbot <syzkaller@googlegroups.com>
    Cc: 赵子轩 <beraphin@gmail.com>
    Cc: Stoyan Manolov <smanolov@suse.de>
    Link: https://lore.kernel.org/r/20220325035827.360418-1-eric.dumazet@gmail.comSigned-off-by: default avatarJakub Kicinski <kuba@kernel.org>
    2d327a79
af_llc.c 32.1 KB