Commit e398fb4b authored by Souptick Joarder's avatar Souptick Joarder Committed by Juergen Gross
Browse files

xen/privcmd: Corrected error handling path 



Previously, if lock_pages() end up partially mapping pages, it used
to return -ERRNO due to which unlock_pages() have to go through
each pages[i] till *nr_pages* to validate them. This can be avoided
by passing correct number of partially mapped pages & -ERRNO separately,
while returning from lock_pages() due to error.

With this fix unlock_pages() doesn't need to validate pages[i] till
*nr_pages* for error scenario and few condition checks can be ignored.

Signed-off-by: default avatarSouptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: default avatarJuergen Gross <jgross@suse.com>
Reviewed-by: default avatarPaul Durrant <paul@xen.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Paul Durrant <xadimgnik@gmail.com>
Link: https://lore.kernel.org/r/1594525195-28345-2-git-send-email-jrdr.linux@gmail.com


Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
parent bcf87687

drivers/xen/privcmd.c

+15 −16
Original line number Diff line number Diff line
@@ -580,13 +580,13 @@ out_unlock: 


static int lock_pages(

	struct privcmd_dm_op_buf kbufs[], unsigned int num,

	struct page *pages[], unsigned int nr_pages)

	struct page *pages[], unsigned int nr_pages, unsigned int *pinned)

{

	unsigned int i;



	for (i = 0; i < num; i++) {

		unsigned int requested;

		int pinned;

		int page_count;



		requested = DIV_ROUND_UP(

			offset_in_page(kbufs[i].uptr) + kbufs[i].size,
@@ -594,14 +594,15 @@ static int lock_pages( 
		if (requested > nr_pages)

			return -ENOSPC;



		pinned = get_user_pages_fast(

		page_count = get_user_pages_fast(

			(unsigned long) kbufs[i].uptr,

			requested, FOLL_WRITE, pages);

		if (pinned < 0)

			return pinned;

		if (page_count < 0)

			return page_count;



		nr_pages -= pinned;

		pages += pinned;

		*pinned += page_count;

		nr_pages -= page_count;

		pages += page_count;

	}



	return 0;
@@ -611,14 +612,9 @@ static void unlock_pages(struct page *pages[], unsigned int nr_pages) 
{

	unsigned int i;



	if (!pages)

		return;



	for (i = 0; i < nr_pages; i++) {

		if (pages[i])

	for (i = 0; i < nr_pages; i++)

		put_page(pages[i]);

}

}



static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)

{
@@ -630,6 +626,7 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata) 
	struct xen_dm_op_buf *xbufs = NULL;

	unsigned int i;

	long rc;

	unsigned int pinned = 0;



	if (copy_from_user(&kdata, udata, sizeof(kdata)))

		return -EFAULT;
@@ -683,9 +680,11 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata) 
		goto out;

	}



	rc = lock_pages(kbufs, kdata.num, pages, nr_pages);

	if (rc)

	rc = lock_pages(kbufs, kdata.num, pages, nr_pages, &pinned);

	if (rc < 0) {

		nr_pages = pinned;

		goto out;

	}



	for (i = 0; i < kdata.num; i++) {

		set_xen_guest_handle(xbufs[i].h, kbufs[i].uptr);

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