Commit 5903c6bd authored by David Vrabel's avatar David Vrabel

xen/gntalloc: safely delete grefs in add_grefs() undo path

If a gref could not be added (perhaps because the limit has been
reached or there are no more grant references available), the undo
path may crash because __del_gref() frees the gref while it is being
used for a list iteration.

A comment suggests that using list_for_each_entry() is safe since the
gref isn't removed from the list being iterated over, but it is freed
and thus list_for_each_entry_safe() must be used.

Also, explicitly delete the gref from the local per-file list, even
though this is not strictly necessary.
Signed-off-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
Reviewed-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
parent e9de2e5f
......@@ -124,7 +124,7 @@ static int add_grefs(struct ioctl_gntalloc_alloc_gref *op,
int i, rc, readonly;
LIST_HEAD(queue_gref);
LIST_HEAD(queue_file);
struct gntalloc_gref *gref;
struct gntalloc_gref *gref, *next;
readonly = !(op->flags & GNTALLOC_FLAG_WRITABLE);
rc = -ENOMEM;
......@@ -160,8 +160,8 @@ static int add_grefs(struct ioctl_gntalloc_alloc_gref *op,
mutex_lock(&gref_mutex);
gref_size -= (op->count - i);
list_for_each_entry(gref, &queue_file, next_file) {
/* __del_gref does not remove from queue_file */
list_for_each_entry_safe(gref, next, &queue_file, next_file) {
list_del(&gref->next_file);
__del_gref(gref);
}
......
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