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    Subject[PATCH AUTOSEL for 4.4 010/115] selinux: check for address length in selinux_socket_bind()
    Date
    From: Alexander Potapenko <glider@google.com>

    [ Upstream commit e2f586bd83177d22072b275edd4b8b872daba924 ]

    KMSAN (KernelMemorySanitizer, a new error detection tool) reports use of
    uninitialized memory in selinux_socket_bind():

    ==================================================================
    BUG: KMSAN: use of unitialized memory
    inter: 0
    CPU: 3 PID: 1074 Comm: packet2 Tainted: G B 4.8.0-rc6+ #1916
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
    0000000000000000 ffff8800882ffb08 ffffffff825759c8 ffff8800882ffa48
    ffffffff818bf551 ffffffff85bab870 0000000000000092 ffffffff85bab550
    0000000000000000 0000000000000092 00000000bb0009bb 0000000000000002
    Call Trace:
    [< inline >] __dump_stack lib/dump_stack.c:15
    [<ffffffff825759c8>] dump_stack+0x238/0x290 lib/dump_stack.c:51
    [<ffffffff818bdee6>] kmsan_report+0x276/0x2e0 mm/kmsan/kmsan.c:1008
    [<ffffffff818bf0fb>] __msan_warning+0x5b/0xb0 mm/kmsan/kmsan_instr.c:424
    [<ffffffff822dae71>] selinux_socket_bind+0xf41/0x1080 security/selinux/hooks.c:4288
    [<ffffffff8229357c>] security_socket_bind+0x1ec/0x240 security/security.c:1240
    [<ffffffff84265d98>] SYSC_bind+0x358/0x5f0 net/socket.c:1366
    [<ffffffff84265a22>] SyS_bind+0x82/0xa0 net/socket.c:1356
    [<ffffffff81005678>] do_syscall_64+0x58/0x70 arch/x86/entry/common.c:292
    [<ffffffff8518217c>] entry_SYSCALL64_slow_path+0x25/0x25 arch/x86/entry/entry_64.o:?
    chained origin: 00000000ba6009bb
    [<ffffffff810bb7a7>] save_stack_trace+0x27/0x50 arch/x86/kernel/stacktrace.c:67
    [< inline >] kmsan_save_stack_with_flags mm/kmsan/kmsan.c:322
    [< inline >] kmsan_save_stack mm/kmsan/kmsan.c:337
    [<ffffffff818bd2b8>] kmsan_internal_chain_origin+0x118/0x1e0 mm/kmsan/kmsan.c:530
    [<ffffffff818bf033>] __msan_set_alloca_origin4+0xc3/0x130 mm/kmsan/kmsan_instr.c:380
    [<ffffffff84265b69>] SYSC_bind+0x129/0x5f0 net/socket.c:1356
    [<ffffffff84265a22>] SyS_bind+0x82/0xa0 net/socket.c:1356
    [<ffffffff81005678>] do_syscall_64+0x58/0x70 arch/x86/entry/common.c:292
    [<ffffffff8518217c>] return_from_SYSCALL_64+0x0/0x6a arch/x86/entry/entry_64.o:?
    origin description: ----address@SYSC_bind (origin=00000000b8c00900)
    ==================================================================

    (the line numbers are relative to 4.8-rc6, but the bug persists upstream)

    , when I run the following program as root:

    =======================================================
    #include <string.h>
    #include <sys/socket.h>
    #include <netinet/in.h>

    int main(int argc, char *argv[]) {
    struct sockaddr addr;
    int size = 0;
    if (argc > 1) {
    size = atoi(argv[1]);
    }
    memset(&addr, 0, sizeof(addr));
    int fd = socket(PF_INET6, SOCK_DGRAM, IPPROTO_IP);
    bind(fd, &addr, size);
    return 0;
    }
    =======================================================

    (for different values of |size| other error reports are printed).

    This happens because bind() unconditionally copies |size| bytes of
    |addr| to the kernel, leaving the rest uninitialized. Then
    security_socket_bind() reads the IP address bytes, including the
    uninitialized ones, to determine the port, or e.g. pass them further to
    sel_netnode_find(), which uses them to calculate a hash.

    Signed-off-by: Alexander Potapenko <glider@google.com>
    Acked-by: Eric Dumazet <edumazet@google.com>
    [PM: fixed some whitespace damage]
    Signed-off-by: Paul Moore <paul@paul-moore.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    security/selinux/hooks.c | 8 ++++++++
    1 file changed, 8 insertions(+)

    diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
    index 3f370eb494d1..4c7db967b7bb 100644
    --- a/security/selinux/hooks.c
    +++ b/security/selinux/hooks.c
    @@ -4124,10 +4124,18 @@ static int selinux_socket_bind(struct socket *sock, struct sockaddr *address, in
    u32 sid, node_perm;

    if (family == PF_INET) {
    + if (addrlen < sizeof(struct sockaddr_in)) {
    + err = -EINVAL;
    + goto out;
    + }
    addr4 = (struct sockaddr_in *)address;
    snum = ntohs(addr4->sin_port);
    addrp = (char *)&addr4->sin_addr.s_addr;
    } else {
    + if (addrlen < SIN6_LEN_RFC2133) {
    + err = -EINVAL;
    + goto out;
    + }
    addr6 = (struct sockaddr_in6 *)address;
    snum = ntohs(addr6->sin6_port);
    addrp = (char *)&addr6->sin6_addr.s6_addr;
    --
    2.14.1
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