Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).
While there, use struct_size() helper, instead of the open-coded
version, to calculate the size for the allocation of the whole
flexible structure, including of course, the flexible-array member.
This code was found with the help of Coccinelle, and audited and
fixed manually.
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/ZSVHurzo/4aFQcT3@work
Signed-off-by: Kees Cook <keescook@chromium.org>
struct buffer {
size_t size;
- char data[];
+ char data[] __counted_by(size);
};
static ssize_t atags_read(struct file *file, char __user *buf,
WARN_ON(tag->hdr.tag != ATAG_NONE);
- b = kmalloc(sizeof(*b) + size, GFP_KERNEL);
+ b = kmalloc(struct_size(b, data, size), GFP_KERNEL);
if (!b)
goto nomem;