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    Subject[PATCH 4.14 03/72] aio: fix spectre gadget in lookup_ioctx
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

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

    From: Jeff Moyer <jmoyer@redhat.com>

    commit a538e3ff9dabcdf6c3f477a373c629213d1c3066 upstream.

    Matthew pointed out that the ioctx_table is susceptible to spectre v1,
    because the index can be controlled by an attacker. The below patch
    should mitigate the attack for all of the aio system calls.

    Cc: stable@vger.kernel.org
    Reported-by: Matthew Wilcox <willy@infradead.org>
    Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
    Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
    Signed-off-by: Jens Axboe <axboe@kernel.dk>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/aio.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/fs/aio.c
    +++ b/fs/aio.c
    @@ -43,6 +43,7 @@

    #include <asm/kmap_types.h>
    #include <linux/uaccess.h>
    +#include <linux/nospec.h>

    #include "internal.h"

    @@ -1084,6 +1085,7 @@ static struct kioctx *lookup_ioctx(unsig
    if (!table || id >= table->nr)
    goto out;

    + id = array_index_nospec(id, table->nr);
    ctx = rcu_dereference(table->table[id]);
    if (ctx && ctx->user_id == ctx_id) {
    if (percpu_ref_tryget_live(&ctx->users))

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