From: Juergen Gross Date: Fri, 25 Feb 2022 15:05:42 +0000 (+0100) Subject: xen/scsifront: don't use gnttab_query_foreign_access() for mapped status X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=f1c85942314dfc400e8526148eee7e8535f995fa;p=linux.git xen/scsifront: don't use gnttab_query_foreign_access() for mapped status Commit 33172ab50a53578a95691310f49567c9266968b0 upstream. It isn't enough to check whether a grant is still being in use by calling gnttab_query_foreign_access(), as a mapping could be realized by the other side just after having called that function. In case the call was done in preparation of revoking a grant it is better to do so via gnttab_try_end_foreign_access() and check the success of that operation instead. This is CVE-2022-23038 / part of XSA-396. Reported-by: Demi Marie Obenour Signed-off-by: Juergen Gross Reviewed-by: Jan Beulich Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/scsi/xen-scsifront.c b/drivers/scsi/xen-scsifront.c index 0204e314b4825..17b8c88840873 100644 --- a/drivers/scsi/xen-scsifront.c +++ b/drivers/scsi/xen-scsifront.c @@ -233,12 +233,11 @@ static void scsifront_gnttab_done(struct vscsifrnt_info *info, return; for (i = 0; i < shadow->nr_grants; i++) { - if (unlikely(gnttab_query_foreign_access(shadow->gref[i]))) { + if (unlikely(!gnttab_try_end_foreign_access(shadow->gref[i]))) { shost_printk(KERN_ALERT, info->host, KBUILD_MODNAME "grant still in use by backend\n"); BUG(); } - gnttab_end_foreign_access(shadow->gref[i], 0, 0UL); } kfree(shadow->sg);