Unverified Commit 35e27a57 authored by Christian Brauner's avatar Christian Brauner
Browse files

fs: keep struct mnt_id_req extensible 



Make it extensible so that we have the liberty to reuse it in future
mount-id based apis. Treat zero size as the first published struct.

Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent d8b0f546

fs/namespace.c

+30 −4
Original line number Diff line number Diff line
@@ -4956,6 +4956,30 @@ static int prepare_kstatmount(struct kstatmount *ks, struct mnt_id_req *kreq, 
	return 0;

}



static int copy_mnt_id_req(const struct mnt_id_req __user *req,

			   struct mnt_id_req *kreq)

{

	int ret;

	size_t usize;



	BUILD_BUG_ON(sizeof(struct mnt_id_req) != MNT_ID_REQ_SIZE_VER0);



	ret = get_user(usize, &req->size);

	if (ret)

		return -EFAULT;

	if (unlikely(usize > PAGE_SIZE))

		return -E2BIG;

	if (unlikely(usize < MNT_ID_REQ_SIZE_VER0))

		return -EINVAL;

	memset(kreq, 0, sizeof(*kreq));

	ret = copy_struct_from_user(kreq, sizeof(*kreq), req, usize);

	if (ret)

		return ret;

	if (kreq->spare != 0)

		return -EINVAL;

	return 0;

}



SYSCALL_DEFINE4(statmount, const struct mnt_id_req __user *, req,

		struct statmount __user *, buf, size_t, bufsize,

		unsigned int, flags)
@@ -4970,8 +4994,9 @@ SYSCALL_DEFINE4(statmount, const struct mnt_id_req __user *, req, 
	if (flags)

		return -EINVAL;



	if (copy_from_user(&kreq, req, sizeof(kreq)))

		return -EFAULT;

	ret = copy_mnt_id_req(req, &kreq);

	if (ret)

		return ret;



retry:

	ret = prepare_kstatmount(&ks, &kreq, buf, bufsize, seq_size);
@@ -5052,8 +5077,9 @@ SYSCALL_DEFINE4(listmount, const struct mnt_id_req __user *, req, 
	if (flags)

		return -EINVAL;



	if (copy_from_user(&kreq, req, sizeof(kreq)))

		return -EFAULT;

	ret = copy_mnt_id_req(req, &kreq);

	if (ret)

		return ret;

	mnt_id = kreq.mnt_id;

	last_mnt_id = kreq.param;

include/uapi/linux/mount.h

+5 −0
Original line number Diff line number Diff line
@@ -184,10 +184,15 @@ struct statmount { 
 * For listmount(2) @param represents the last listed mount id (or zero).

 */

struct mnt_id_req {

	__u32 size;

	__u32 spare;

	__u64 mnt_id;

	__u64 param;

};



/* List of all mnt_id_req versions. */

#define MNT_ID_REQ_SIZE_VER0	24 /* sizeof first published struct */



/*

 * @mask bits for statmount(2)

 */