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    Subject[PATCH 3.16 305/306] net: avoid signed overflows for SO_{SND|RCV}BUFFORCE
    3.16.40-rc1 review patch.  If anyone has any objections, please let me know.

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

    From: Eric Dumazet <edumazet@google.com>

    commit b98b0bc8c431e3ceb4b26b0dfc8db509518fb290 upstream.

    CAP_NET_ADMIN users should not be allowed to set negative
    sk_sndbuf or sk_rcvbuf values, as it can lead to various memory
    corruptions, crashes, OOM...

    Note that before commit 82981930125a ("net: cleanups in
    sock_setsockopt()"), the bug was even more serious, since SO_SNDBUF
    and SO_RCVBUF were vulnerable.

    This needs to be backported to all known linux kernels.

    Again, many thanks to syzkaller team for discovering this gem.

    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Reported-by: Andrey Konovalov <andreyknvl@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    net/core/sock.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/net/core/sock.c
    +++ b/net/core/sock.c
    @@ -749,7 +749,7 @@ int sock_setsockopt(struct socket *sock,
    val = min_t(u32, val, sysctl_wmem_max);
    set_sndbuf:
    sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
    - sk->sk_sndbuf = max_t(u32, val * 2, SOCK_MIN_SNDBUF);
    + sk->sk_sndbuf = max_t(int, val * 2, SOCK_MIN_SNDBUF);
    /* Wake up sending tasks if we upped the value. */
    sk->sk_write_space(sk);
    break;
    @@ -785,7 +785,7 @@ set_rcvbuf:
    * returning the value we actually used in getsockopt
    * is the most desirable behavior.
    */
    - sk->sk_rcvbuf = max_t(u32, val * 2, SOCK_MIN_RCVBUF);
    + sk->sk_rcvbuf = max_t(int, val * 2, SOCK_MIN_RCVBUF);
    break;

    case SO_RCVBUFFORCE:
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