[PATCH 4.19 114/125] USB: gadget: u_f: add overflow checks to VLA macros

Greg Kroah-Hartman
2020-09-01T16:51:53Z

From: Brooke Basile <brookebasile@gmail.com>

commit b1cd1b65afba95971fa457dfdb2c941c60d38c5b upstream.

size can potentially hold an overflowed value if its assigned expression
is left unchecked, leading to a smaller than needed allocation when
vla_group_size() is used by callers to allocate memory.
To fix this, add a test for saturation before declaring variables and an
overflow check to (n) * sizeof(type).
If the expression results in overflow, vla_group_size() will return SIZE_MAX.

Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Brooke Basile <brookebasile@gmail.com>
Acked-by: Felipe Balbi <balbi@kernel.org>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/gadget/u_f.h | 38 +++++++++++++++++++++++++++-----------
1 file changed, 27 insertions(+), 11 deletions(-)

--- a/drivers/usb/gadget/u_f.h
+++ b/drivers/usb/gadget/u_f.h
@@ -14,6 +14,7 @@
#define __U_F_H__

#include <linux/usb/gadget.h>
+#include <linux/overflow.h>

/* Variable Length Array Macros **********************************************/
#define vla_group(groupname) size_t groupname##__next = 0
@@ -21,21 +22,36 @@

#define vla_item(groupname, type, name, n) \
size_t groupname##_##name##__offset = ({ \
- size_t align_mask = __alignof__(type) - 1; \
- size_t offset = (groupname##__next + align_mask) & ~align_mask;\
- size_t size = (n) * sizeof(type); \
- groupname##__next = offset + size; \
+ size_t offset = 0; \
+ if (groupname##__next != SIZE_MAX) { \
+ size_t align_mask = __alignof__(type) - 1; \
+ size_t offset = (groupname##__next + align_mask) \
+ & ~align_mask; \
+ size_t size = array_size(n, sizeof(type)); \
+ if (check_add_overflow(offset, size, \
+ &groupname##__next)) { \
+ groupname##__next = SIZE_MAX; \
+ offset = 0; \
+ } \
+ } \
offset; \
})

#define vla_item_with_sz(groupname, type, name, n) \
- size_t groupname##_##name##__sz = (n) * sizeof(type); \
- size_t groupname##_##name##__offset = ({ \
- size_t align_mask = __alignof__(type) - 1; \
- size_t offset = (groupname##__next + align_mask) & ~align_mask;\
- size_t size = groupname##_##name##__sz; \
- groupname##__next = offset + size; \
- offset; \
+ size_t groupname##_##name##__sz = array_size(n, sizeof(type)); \
+ size_t groupname##_##name##__offset = ({ \
+ size_t offset = 0; \
+ if (groupname##__next != SIZE_MAX) { \
+ size_t align_mask = __alignof__(type) - 1; \
+ size_t offset = (groupname##__next + align_mask) \
+ & ~align_mask; \
+ if (check_add_overflow(offset, groupname##_##name##__sz,\
+ &groupname##__next)) { \
+ groupname##__next = SIZE_MAX; \
+ offset = 0; \
+ } \
+ } \
+ offset; \
})

#define vla_ptr(ptr, groupname, name) \