• Jiri Slaby's avatar
    net: sctp, forbid negative length · a4b8e71b
    Jiri Slaby authored
    Most of getsockopt handlers in net/sctp/socket.c check len against
    sizeof some structure like:
            if (len < sizeof(int))
                    return -EINVAL;
    On the first look, the check seems to be correct. But since len is int
    and sizeof returns size_t, int gets promoted to unsigned size_t too. So
    the test returns false for negative lengths. Yes, (-1 < sizeof(long)) is
    Fix this in sctp by explicitly checking len < 0 before any getsockopt
    handler is called.
    Note that sctp_getsockopt_events already handled the negative case.
    Since we added the < 0 check elsewhere, this one can be removed.
    If not checked, this is the result:
    UBSAN: Undefined behaviour in ../mm/page_alloc.c:2722:19
    shift exponent 52 is too large for 32-bit type 'int'
    CPU: 1 PID: 24535 Comm: syz-executor Not tainted 4.8.1-0-syzkaller #1
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014
     0000000000000000 ffff88006d99f2a8 ffffffffb2f7bdea 0000000041b58ab3
     ffffffffb4363c14 ffffffffb2f7bcde ffff88006d99f2d0 ffff88006d99f270
     0000000000000000 0000000000000000 0000000000000034 ffffffffb5096422
    Call Trace:
     [<ffffffffb3051498>] ? __ubsan_handle_shift_out_of_bounds+0x29c/0x300
     [<ffffffffb273f0e4>] ? kmalloc_order+0x24/0x90
     [<ffffffffb27416a4>] ? kmalloc_order_trace+0x24/0x220
     [<ffffffffb2819a30>] ? __kmalloc+0x330/0x540
     [<ffffffffc18c25f4>] ? sctp_getsockopt_local_addrs+0x174/0xca0 [sctp]
     [<ffffffffc18d2bcd>] ? sctp_getsockopt+0x10d/0x1b0 [sctp]
     [<ffffffffb37c1219>] ? sock_common_getsockopt+0xb9/0x150
     [<ffffffffb37be2f5>] ? SyS_getsockopt+0x1a5/0x270
    Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
    Cc: Vlad Yasevich <vyasevich@gmail.com>
    Cc: Neil Horman <nhorman@tuxdriver.com>
    Cc: "David S. Miller" <davem@davemloft.net>
    Cc: linux-sctp@vger.kernel.org
    Cc: netdev@vger.kernel.org
    Acked-by: default avatarNeil Horman <nhorman@tuxdriver.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
socket.c 219 KB