[PATCH v3 08/16] device: Use overflow helpers for devm_kmalloc()

[Kees Cook]

Use the overflow helpers both in existing multiplication-using inlines as
well as the addition-overflow case in the core allocation routine.

Signed-off-by: Kees Cook <keesc...@chromium.org>
---
 drivers/base/devres.c  | 7 ++++++-
 include/linux/device.h | 8 ++++++--
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index 95b67281cd2a..f98a097e73f2 100644
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -84,9 +84,14 @@ static struct devres_group * node_to_group(struct 
devres_node *node)
 static __always_inline struct devres * alloc_dr(dr_release_t release,
                                                size_t size, gfp_t gfp, int nid)
 {
-       size_t tot_size = sizeof(struct devres) + size;
+       size_t tot_size;
        struct devres *dr;
 
+       /* We must catch any near-SIZE_MAX cases that could overflow. */
+       if (unlikely(check_add_overflow(sizeof(struct devres), size,
+                                       &tot_size)))
+               return NULL;
+
        dr = kmalloc_node_track_caller(tot_size, gfp, nid);
        if (unlikely(!dr))
                return NULL;
diff --git a/include/linux/device.h b/include/linux/device.h
index 477956990f5e..897efa647203 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -25,6 +25,7 @@
 #include <linux/ratelimit.h>
 #include <linux/uidgid.h>
 #include <linux/gfp.h>
+#include <linux/overflow.h>
 #include <asm/device.h>
 
 struct device;
@@ -668,9 +669,12 @@ static inline void *devm_kzalloc(struct device *dev, 
size_t size, gfp_t gfp)
 static inline void *devm_kmalloc_array(struct device *dev,
                                       size_t n, size_t size, gfp_t flags)
 {
-       if (size != 0 && n > SIZE_MAX / size)
+       size_t bytes;
+
+       if (unlikely(check_mul_overflow(n, size, &bytes)))
                return NULL;
-       return devm_kmalloc(dev, n * size, flags);
+
+       return devm_kmalloc(dev, bytes, flags);
 }
 static inline void *devm_kcalloc(struct device *dev,
                                 size_t n, size_t size, gfp_t flags)
-- 
2.17.0