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    Subject[ 065/143] net: check net.core.somaxconn sysctl values
    2.6.32-longterm review patch.  If anyone has any objections, please let me know.

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

    From: Roman Gushchin <klamm@yandex-team.ru>

    [ Upstream commit 5f671d6b4ec3e6d66c2a868738af2cdea09e7509 ]

    It's possible to assign an invalid value to the net.core.somaxconn
    sysctl variable, because there is no checks at all.

    The sk_max_ack_backlog field of the sock structure is defined as
    unsigned short. Therefore, the backlog argument in inet_listen()
    shouldn't exceed USHRT_MAX. The backlog argument in the listen() syscall
    is truncated to the somaxconn value. So, the somaxconn value shouldn't
    exceed 65535 (USHRT_MAX).
    Also, negative values of somaxconn are meaningless.

    before:
    $ sysctl -w net.core.somaxconn=256
    net.core.somaxconn = 256
    $ sysctl -w net.core.somaxconn=65536
    net.core.somaxconn = 65536
    $ sysctl -w net.core.somaxconn=-100
    net.core.somaxconn = -100

    after:
    $ sysctl -w net.core.somaxconn=256
    net.core.somaxconn = 256
    $ sysctl -w net.core.somaxconn=65536
    error: "Invalid argument" setting key "net.core.somaxconn"
    $ sysctl -w net.core.somaxconn=-100
    error: "Invalid argument" setting key "net.core.somaxconn"

    Based on a prior patch from Changli Gao.

    Signed-off-by: Roman Gushchin <klamm@yandex-team.ru>
    Reported-by: Changli Gao <xiaosuo@gmail.com>
    Suggested-by: Eric Dumazet <edumazet@google.com>
    Acked-by: Eric Dumazet <edumazet@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Willy Tarreau <w@1wt.eu>
    ---
    net/core/sysctl_net_core.c | 7 ++++++-
    1 file changed, 6 insertions(+), 1 deletion(-)

    diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
    index 7db1de0..e2eaf29 100644
    --- a/net/core/sysctl_net_core.c
    +++ b/net/core/sysctl_net_core.c
    @@ -14,6 +14,9 @@
    #include <net/ip.h>
    #include <net/sock.h>

    +static int zero = 0;
    +static int ushort_max = 65535;
    +
    static struct ctl_table net_core_table[] = {
    #ifdef CONFIG_NET
    {
    @@ -116,7 +119,9 @@ static struct ctl_table netns_core_table[] = {
    .data = &init_net.core.sysctl_somaxconn,
    .maxlen = sizeof(int),
    .mode = 0644,
    - .proc_handler = proc_dointvec
    + .extra1 = &zero,
    + .extra2 = &ushort_max,
    + .proc_handler = proc_dointvec_minmax
    },
    { .ctl_name = 0 }
    };
    --
    1.7.12.2.21.g234cd45.dirty




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