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    Subject[PATCH 4.14 42/62] net: atm: Fix potential Spectre v1
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

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

    From: Gustavo A. R. Silva <gustavo@embeddedor.com>

    commit acf784bd0ce257fe43da7ca266f7a10b837479d2 upstream.

    ioc_data.dev_num can be controlled by user-space, hence leading to
    a potential exploitation of the Spectre variant 1 vulnerability.

    This issue was detected with the help of Smatch:
    net/atm/lec.c:702 lec_vcc_attach() warn: potential spectre issue
    'dev_lec'

    Fix this by sanitizing ioc_data.dev_num before using it to index
    dev_lec. Also, notice that there is another instance in which array
    dev_lec is being indexed using ioc_data.dev_num at line 705:
    lec_vcc_added(netdev_priv(dev_lec[ioc_data.dev_num]),

    Notice that given that speculation windows are large, the policy is
    to kill the speculation on the first load and not worry if it can be
    completed with a dependent load/store [1].

    [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2

    Cc: stable@vger.kernel.org
    Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    net/atm/lec.c | 9 +++++++--
    1 file changed, 7 insertions(+), 2 deletions(-)

    --- a/net/atm/lec.c
    +++ b/net/atm/lec.c
    @@ -41,6 +41,9 @@ static unsigned char bridge_ula_lec[] =
    #include <linux/module.h>
    #include <linux/init.h>

    +/* Hardening for Spectre-v1 */
    +#include <linux/nospec.h>
    +
    #include "lec.h"
    #include "lec_arpc.h"
    #include "resources.h"
    @@ -687,8 +690,10 @@ static int lec_vcc_attach(struct atm_vcc
    bytes_left = copy_from_user(&ioc_data, arg, sizeof(struct atmlec_ioc));
    if (bytes_left != 0)
    pr_info("copy from user failed for %d bytes\n", bytes_left);
    - if (ioc_data.dev_num < 0 || ioc_data.dev_num >= MAX_LEC_ITF ||
    - !dev_lec[ioc_data.dev_num])
    + if (ioc_data.dev_num < 0 || ioc_data.dev_num >= MAX_LEC_ITF)
    + return -EINVAL;
    + ioc_data.dev_num = array_index_nospec(ioc_data.dev_num, MAX_LEC_ITF);
    + if (!dev_lec[ioc_data.dev_num])
    return -EINVAL;
    vpriv = kmalloc(sizeof(struct lec_vcc_priv), GFP_KERNEL);
    if (!vpriv)

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