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xen/privcmd: Corrected error handling path

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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: Souptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Paul 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: Juergen Gross <jgross@suse.com>
This commit is contained in:
Souptick Joarder 2020-07-12 09:09:53 +05:30 committed by Juergen Gross
parent bcf876870b
commit e398fb4bdf
1 changed files with 15 additions and 16 deletions
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31
drivers/xen/privcmd.c
View file

@ -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;
@ -611,13 +612,8 @@ 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])
put_page(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);