From: Juergen Gross jgross@suse.com
commit c5deb27895e017a0267de0a20d140ad5fcc55a54 upstream.
The error exit of privcmd_ioctl_dm_op() is calling unlock_pages() potentially with pages being NULL, leading to a NULL dereference.
Additionally lock_pages() doesn't check for pin_user_pages_fast() having been completely successful, resulting in potentially not locking all pages into memory. This could result in sporadic failures when using the related memory in user mode.
Fix all of that by calling unlock_pages() always with the real number of pinned pages, which will be zero in case pages being NULL, and by checking the number of pages pinned by pin_user_pages_fast() matching the expected number of pages.
Cc: stable@vger.kernel.org Fixes: ab520be8cd5d ("xen/privcmd: Add IOCTL_PRIVCMD_DM_OP") Reported-by: Rustam Subkhankulov subkhankulov@ispras.ru Signed-off-by: Juergen Gross jgross@suse.com Reviewed-by: Jan Beulich jbeulich@suse.com Reviewed-by: Oleksandr Tyshchenko oleksandr_tyshchenko@epam.com Link: https://lore.kernel.org/r/20220825141918.3581-1-jgross@suse.com Signed-off-by: Juergen Gross jgross@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/xen/privcmd.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-)
--- a/drivers/xen/privcmd.c +++ b/drivers/xen/privcmd.c @@ -581,27 +581,30 @@ static int lock_pages( struct privcmd_dm_op_buf kbufs[], unsigned int num, struct page *pages[], unsigned int nr_pages, unsigned int *pinned) { - unsigned int i; + unsigned int i, off = 0;
- for (i = 0; i < num; i++) { + for (i = 0; i < num; ) { unsigned int requested; int page_count;
requested = DIV_ROUND_UP( offset_in_page(kbufs[i].uptr) + kbufs[i].size, - PAGE_SIZE); + PAGE_SIZE) - off; if (requested > nr_pages) return -ENOSPC;
page_count = pin_user_pages_fast( - (unsigned long) kbufs[i].uptr, + (unsigned long)kbufs[i].uptr + off * PAGE_SIZE, requested, FOLL_WRITE, pages); - if (page_count < 0) - return page_count; + if (page_count <= 0) + return page_count ? : -EFAULT;
*pinned += page_count; nr_pages -= page_count; pages += page_count; + + off = (requested == page_count) ? 0 : off + page_count; + i += !off; }
return 0; @@ -677,10 +680,8 @@ static long privcmd_ioctl_dm_op(struct f }
rc = lock_pages(kbufs, kdata.num, pages, nr_pages, &pinned); - if (rc < 0) { - nr_pages = pinned; + if (rc < 0) goto out; - }
for (i = 0; i < kdata.num; i++) { set_xen_guest_handle(xbufs[i].h, kbufs[i].uptr); @@ -692,7 +693,7 @@ static long privcmd_ioctl_dm_op(struct f xen_preemptible_hcall_end();
out: - unlock_pages(pages, nr_pages); + unlock_pages(pages, pinned); kfree(xbufs); kfree(pages); kfree(kbufs);