[PATCH 4.9 078/103] IB/core: Add mitigation for Spectre V1

Greg Kroah-Hartman
2019-08-22T17:39:43Z

[ Upstream commit 61f259821dd3306e49b7d42a3f90fb5a4ff3351b ]

Some processors may mispredict an array bounds check and
speculatively access memory that they should not. With
a user supplied array index we like to play things safe
by masking the value with the array size before it is
used as an index.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20190731043957.GA1600@agluck-desk2.amr.corp.intel.com
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/infiniband/core/user_mad.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/core/user_mad.c b/drivers/infiniband/core/user_mad.c
index 415a3185cde7f..cf93a96b63249 100644
--- a/drivers/infiniband/core/user_mad.c
+++ b/drivers/infiniband/core/user_mad.c
@@ -49,6 +49,7 @@
#include <linux/sched.h>
#include <linux/semaphore.h>
#include <linux/slab.h>
+#include <linux/nospec.h>

#include <asm/uaccess.h>

@@ -843,11 +844,14 @@ static int ib_umad_unreg_agent(struct ib_umad_file *file, u32 __user *arg)

if (get_user(id, arg))
return -EFAULT;
+ if (id >= IB_UMAD_MAX_AGENTS)
+ return -EINVAL;

mutex_lock(&file->port->file_mutex);
mutex_lock(&file->mutex);

- if (id >= IB_UMAD_MAX_AGENTS || !__get_agent(file, id)) {
+ id = array_index_nospec(id, IB_UMAD_MAX_AGENTS);
+ if (!__get_agent(file, id)) {
ret = -EINVAL;
goto out;
}
--
2.20.1