Commit ac7110d8 authored by Gustavo A. R. Silva's avatar Gustavo A. R. Silva Committed by Kees Cook
Browse files

atags_proc: Add __counted_by for struct buffer and use struct_size() 



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: default avatarGustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarJustin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/ZSVHurzo/4aFQcT3@work


Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent 8a3750ec

arch/arm/kernel/atags_proc.c

+2 −2
Original line number Diff line number Diff line
@@ -7,7 +7,7 @@ 


struct buffer {

	size_t size;

	char data[];

	char data[] __counted_by(size);

};



static ssize_t atags_read(struct file *file, char __user *buf,
@@ -54,7 +54,7 @@ static int __init init_atags_procfs(void) 


	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;