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    Subject[PATCH 4.14 109/138] sctp: sctp_sockaddr_af must check minimal addr length for AF_INET6
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Eric Dumazet <edumazet@google.com>


    [ Upstream commit 81e98370293afcb58340ce8bd71af7b97f925c26 ]

    Check must happen before call to ipv6_addr_v4mapped()

    syzbot report was :

    BUG: KMSAN: uninit-value in sctp_sockaddr_af net/sctp/socket.c:359 [inline]
    BUG: KMSAN: uninit-value in sctp_do_bind+0x60f/0xdc0 net/sctp/socket.c:384
    CPU: 0 PID: 3576 Comm: syzkaller968804 Not tainted 4.16.0+ #82
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
    Call Trace:
    __dump_stack lib/dump_stack.c:17 [inline]
    dump_stack+0x185/0x1d0 lib/dump_stack.c:53
    kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
    __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
    sctp_sockaddr_af net/sctp/socket.c:359 [inline]
    sctp_do_bind+0x60f/0xdc0 net/sctp/socket.c:384
    sctp_bind+0x149/0x190 net/sctp/socket.c:332
    inet6_bind+0x1fd/0x1820 net/ipv6/af_inet6.c:293
    SYSC_bind+0x3f2/0x4b0 net/socket.c:1474
    SyS_bind+0x54/0x80 net/socket.c:1460
    do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
    entry_SYSCALL_64_after_hwframe+0x3d/0xa2
    RIP: 0033:0x43fd49
    RSP: 002b:00007ffe99df3d28 EFLAGS: 00000213 ORIG_RAX: 0000000000000031
    RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043fd49
    RDX: 0000000000000010 RSI: 0000000020000000 RDI: 0000000000000003
    RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
    R10: 00000000004002c8 R11: 0000000000000213 R12: 0000000000401670
    R13: 0000000000401700 R14: 0000000000000000 R15: 0000000000000000

    Local variable description: ----address@SYSC_bind
    Variable was created at:
    SYSC_bind+0x6f/0x4b0 net/socket.c:1461
    SyS_bind+0x54/0x80 net/socket.c:1460

    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Cc: Vlad Yasevich <vyasevich@gmail.com>
    Cc: Neil Horman <nhorman@tuxdriver.com>
    Reported-by: syzbot <syzkaller@googlegroups.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/sctp/socket.c | 13 ++++++++-----
    1 file changed, 8 insertions(+), 5 deletions(-)

    --- a/net/sctp/socket.c
    +++ b/net/sctp/socket.c
    @@ -337,11 +337,14 @@ static struct sctp_af *sctp_sockaddr_af(
    if (!opt->pf->af_supported(addr->sa.sa_family, opt))
    return NULL;

    - /* V4 mapped address are really of AF_INET family */
    - if (addr->sa.sa_family == AF_INET6 &&
    - ipv6_addr_v4mapped(&addr->v6.sin6_addr) &&
    - !opt->pf->af_supported(AF_INET, opt))
    - return NULL;
    + if (addr->sa.sa_family == AF_INET6) {
    + if (len < SIN6_LEN_RFC2133)
    + return NULL;
    + /* V4 mapped address are really of AF_INET family */
    + if (ipv6_addr_v4mapped(&addr->v6.sin6_addr) &&
    + !opt->pf->af_supported(AF_INET, opt))
    + return NULL;
    + }

    /* If we get this far, af is valid. */
    af = sctp_get_af_specific(addr->sa.sa_family);

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