Commit 762a3af6 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Linus Torvalds
Browse files

exec: open code copy_string_kernel 



Currently copy_string_kernel is just a wrapper around copy_strings that
simplifies the calling conventions and uses set_fs to allow passing a
kernel pointer.  But due to the fact the we only need to handle a single
kernel argument pointer, the logic can be sigificantly simplified while
getting rid of the set_fs.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Link: http://lkml.kernel.org/r/20200501104105.2621149-3-hch@lst.de


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 986db2d1

fs/exec.c

+34 −9
Original line number Diff line number Diff line
@@ -592,17 +592,42 @@ static int copy_strings(int argc, struct user_arg_ptr argv, 
 */

int copy_string_kernel(const char *arg, struct linux_binprm *bprm)

{

	int r;

	mm_segment_t oldfs = get_fs();

	struct user_arg_ptr argv = {

		.ptr.native = (const char __user *const  __user *)&arg,

	};

	int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */;

	unsigned long pos = bprm->p;



	if (len == 0)

		return -EFAULT;

	if (!valid_arg_len(bprm, len))

		return -E2BIG;



	/* We're going to work our way backwards. */

	arg += len;

	bprm->p -= len;

	if (IS_ENABLED(CONFIG_MMU) && bprm->p < bprm->argmin)

		return -E2BIG;



	while (len > 0) {

		unsigned int bytes_to_copy = min_t(unsigned int, len,

				min_not_zero(offset_in_page(pos), PAGE_SIZE));

		struct page *page;

		char *kaddr;



		pos -= bytes_to_copy;

		arg -= bytes_to_copy;

		len -= bytes_to_copy;



	set_fs(KERNEL_DS);

	r = copy_strings(1, argv, bprm);

	set_fs(oldfs);

		page = get_arg_page(bprm, pos, 1);

		if (!page)

			return -E2BIG;

		kaddr = kmap_atomic(page);

		flush_arg_page(bprm, pos & PAGE_MASK, page);

		memcpy(kaddr + offset_in_page(pos), arg, bytes_to_copy);

		flush_kernel_dcache_page(page);

		kunmap_atomic(kaddr);

		put_arg_page(page);

	}



	return r;

	return 0;

}

EXPORT_SYMBOL(copy_string_kernel);