• Eric Dumazet's avatar
    llc: better deal with too small mtu · 1e22ffab
    Eric Dumazet authored
    [ Upstream commit 2c5d5b13 ]
    
    syzbot loves to set very small mtu on devices, since it brings joy.
    We must make llc_ui_sendmsg() fool proof.
    
    usercopy: Kernel memory overwrite attempt detected to wrapped address (offset 0, size 18446612139802320068)!
    
    kernel BUG at mm/usercopy.c:100!
    invalid opcode: 0000 [#1] SMP KASAN
    Dumping ftrace buffer:
       (ftrace buffer empty)
    Modules linked in:
    CPU: 0 PID: 17464 Comm: syz-executor1 Not tainted 4.17.0-rc3+ #36
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
    RIP: 0010:usercopy_abort+0xbb/0xbd mm/usercopy.c:88
    RSP: 0018:ffff8801868bf800 EFLAGS: 00010282
    RAX: 000000000000006c RBX: ffffffff87d2fb00 RCX: 0000000000000000
    RDX: 000000000000006c RSI: ffffffff81610731 RDI: ffffed0030d17ef6
    RBP: ffff8801868bf858 R08: ffff88018daa4200 R09: ffffed003b5c4fb0
    R10: ffffed003b5c4fb0 R11: ffff8801dae27d87 R12: ffffffff87d2f8e0
    R13: ffffffff87d2f7a0 R14: ffffffff87d2f7a0 R15: ffffffff87d2f7a0
    FS:  00007f56a14ac700(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 0000001b2bc21000 CR3: 00000001abeb1000 CR4: 00000000001426f0
    DR0: 0000000020000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000030602
    Call Trace:
     check_bogus_address mm/usercopy.c:153 [inline]
     __check_object_size+0x5d9/0x5d9 mm/usercopy.c:256
     check_object_size include/linux/thread_info.h:108 [inline]
     check_copy_size include/linux/thread_info.h:139 [inline]
     copy_from_iter_full include/linux/uio.h:121 [inline]
     memcpy_from_msg include/linux/skbuff.h:3305 [inline]
     llc_ui_sendmsg+0x4b1/0x1530 net/llc/af_llc.c:941
     sock_sendmsg_nosec net/socket.c:629 [inline]
     sock_sendmsg+0xd5/0x120 net/socket.c:639
     __sys_sendto+0x3d7/0x670 net/socket.c:1789
     __do_sys_sendto net/socket.c:1801 [inline]
     __se_sys_sendto net/socket.c:1797 [inline]
     __x64_sys_sendto+0xe1/0x1a0 net/socket.c:1797
     do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
     entry_SYSCALL_64_after_hwframe+0x49/0xbe
    RIP: 0033:0x455979
    RSP: 002b:00007f56a14abc68 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
    RAX: ffffffffffffffda RBX: 00007f56a14ac6d4 RCX: 0000000000455979
    RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000018
    RBP: 000000000072bea0 R08: 00000000200012c0 R09: 0000000000000010
    R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
    R13: 0000000000000548 R14: 00000000006fbf60 R15: 0000000000000000
    Code: 55 c0 e8 c0 55 bb ff ff 75 c8 48 8b 55 c0 4d 89 f9 ff 75 d0 4d 89 e8 48 89 d9 4c 89 e6 41 56 48 c7 c7 80 fa d2 87 e8 a0 0b a3 ff <0f> 0b e8 95 55 bb ff e8 c0 a8 f7 ff 8b 95 14 ff ff ff 4d 89 e8
    RIP: usercopy_abort+0xbb/0xbd mm/usercopy.c:88 RSP: ffff8801868bf800
    
    Fixes: 1da177e4 ("Linux-2.6.12-rc2")
    Signed-off-by: 's avatarEric Dumazet <edumazet@google.com>
    Reported-by: 's avatarsyzbot <syzkaller@googlegroups.com>
    Signed-off-by: 's avatarDavid S. Miller <davem@davemloft.net>
    Signed-off-by: 's avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    1e22ffab