• Eric Dumazet's avatar
    net: rose: fix a possible stack overflow · 8cf288b5
    Eric Dumazet authored
    [ Upstream commit e5dcc0c3 ]
    
    rose_write_internal() uses a temp buffer of 100 bytes, but a manual
    inspection showed that given arbitrary input, rose_create_facilities()
    can fill up to 110 bytes.
    
    Lets use a tailroom of 256 bytes for peace of mind, and remove
    the bounce buffer : we can simply allocate a big enough skb
    and adjust its length as needed.
    
    syzbot report :
    
    BUG: KASAN: stack-out-of-bounds in memcpy include/linux/string.h:352 [inline]
    BUG: KASAN: stack-out-of-bounds in rose_create_facilities net/rose/rose_subr.c:521 [inline]
    BUG: KASAN: stack-out-of-bounds in rose_write_internal+0x597/0x15d0 net/rose/rose_subr.c:116
    Write of size 7 at addr ffff88808b1ffbef by task syz-executor.0/24854
    
    CPU: 0 PID: 24854 Comm: syz-executor.0 Not tainted 5.0.0+ #97
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
    Call Trace:
     __dump_stack lib/dump_stack.c:77 [inline]
     dump_stack+0x172/0x1f0 lib/dump_stack.c:113
     print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
     kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
     check_memory_region_inline mm/kasan/generic.c:185 [inline]
     check_memory_region+0x123/0x190 mm/kasan/generic.c:191
     memcpy+0x38/0x50 mm/kasan/common.c:131
     memcpy include/linux/string.h:352 [inline]
     rose_create_facilities net/rose/rose_subr.c:521 [inline]
     rose_write_internal+0x597/0x15d0 net/rose/rose_subr.c:116
     rose_connect+0x7cb/0x1510 net/rose/af_rose.c:826
     __sys_connect+0x266/0x330 net/socket.c:1685
     __do_sys_connect net/socket.c:1696 [inline]
     __se_sys_connect net/socket.c:1693 [inline]
     __x64_sys_connect+0x73/0xb0 net/socket.c:1693
     do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
     entry_SYSCALL_64_after_hwframe+0x49/0xbe
    RIP: 0033:0x458079
    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:00007f47b8d9dc78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
    RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458079
    RDX: 000000000000001c RSI: 0000000020000040 RDI: 0000000000000004
    RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
    R10: 0000000000000000 R11: 0000000000000246 R12: 00007f47b8d9e6d4
    R13: 00000000004be4a4 R14: 00000000004ceca8 R15: 00000000ffffffff
    
    The buggy address belongs to the page:
    page:ffffea00022c7fc0 count:0 mapcount:0 mapping:0000000000000000 index:0x0
    flags: 0x1fffc0000000000()
    raw: 01fffc0000000000 0000000000000000 ffffffff022c0101 0000000000000000
    raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
    page dumped because: kasan: bad access detected
    
    Memory state around the buggy address:
     ffff88808b1ffa80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
     ffff88808b1ffb00: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 00 00 03
    >ffff88808b1ffb80: f2 f2 00 00 00 00 00 00 00 00 00 00 00 00 04 f3
                                                                 ^
     ffff88808b1ffc00: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
     ffff88808b1ffc80: 00 00 00 00 00 00 00 f1 f1 f1 f1 f1 f1 01 f2 01
    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>
    8cf288b5
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