Commit 5f4610fe authored by Jeff Moyer's avatar Jeff Moyer Committed by Greg Kroah-Hartman

aio: fix spectre gadget in lookup_ioctx

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: default avatarMatthew Wilcox <willy@infradead.org>
Reported-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: default avatarJeff Moyer <jmoyer@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 7ff0bcb2
......@@ -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(unsigned long ctx_id)
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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