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USB: gadget: u_f: add overflow checks to VLA macros 

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>
zero-sugar-mainline-defconfig
Brooke Basile 2020-08-25 09:05:08 -04:00 committed by Greg Kroah-Hartman
parent f1ec7ae6c9
commit b1cd1b65af
1 changed files with 27 additions and 11 deletions
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38
drivers/usb/gadget/u_f.h
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@ -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) \