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    Subject[PATCH 4.14 16/31] RDMA/ucma: Fix Spectre v1 vulnerability
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

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

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

    commit a3671a4f973ee9d9621d60166cc3b037c397d604 upstream.

    hdr.cmd can be indirectly 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:

    drivers/infiniband/core/ucma.c:1686 ucma_write() warn: potential
    spectre issue 'ucma_cmd_table' [r] (local cap)

    Fix this by sanitizing hdr.cmd before using it to index
    ucm_cmd_table.

    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: Doug Ledford <dledford@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/infiniband/core/ucma.c | 3 +++
    1 file changed, 3 insertions(+)

    --- a/drivers/infiniband/core/ucma.c
    +++ b/drivers/infiniband/core/ucma.c
    @@ -44,6 +44,8 @@
    #include <linux/module.h>
    #include <linux/nsproxy.h>

    +#include <linux/nospec.h>
    +
    #include <rdma/rdma_user_cm.h>
    #include <rdma/ib_marshall.h>
    #include <rdma/rdma_cm.h>
    @@ -1659,6 +1661,7 @@ static ssize_t ucma_write(struct file *f

    if (hdr.cmd >= ARRAY_SIZE(ucma_cmd_table))
    return -EINVAL;
    + hdr.cmd = array_index_nospec(hdr.cmd, ARRAY_SIZE(ucma_cmd_table));

    if (hdr.in + sizeof(hdr) > len)
    return -EINVAL;

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