The currently lockless access to the xen console list in
vtermno_to_xencons() is incorrect, as additions and removals from the
list can happen anytime, and as such the traversal of the list to get
the private console data for a given termno needs to happen with the
lock held. Note users that modify the list already do so with the
lock taken.
While there switch from using list_for_each_entry_safe to
list_for_each_entry: the current entry cursor won't be removed as
part of the code in the loop body, so using the _safe variant is
pointless.
Fixes: 02e19f9c7cac ('hvc_xen: implement multiconsole support')
Signed-off-by: Roger Pau Monné <roger....@citrix.com>
---
drivers/tty/hvc/hvc_xen.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
index d65741983837..117dc48f980e 100644
--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c
@@ -53,17 +53,22 @@ static DEFINE_SPINLOCK(xencons_lock);
static struct xencons_info *vtermno_to_xencons(int vtermno)
{
- struct xencons_info *entry, *n, *ret = NULL;
+ struct xencons_info *entry, *ret = NULL;
+ unsigned long flags;
- if (list_empty(&xenconsoles))
- return NULL;
+ spin_lock_irqsave(&xencons_lock, flags);
+ if (list_empty(&xenconsoles)) {
+ spin_unlock_irqrestore(&xencons_lock, flags);
+ return NULL;
+ }
- list_for_each_entry_safe(entry, n, &xenconsoles, list) {
+ list_for_each_entry(entry, &xenconsoles, list) {
if (entry->vtermno == vtermno) {
ret = entry;
break;
}
}
+ spin_unlock_irqrestore(&xencons_lock, flags);
return ret;
}
--
2.37.3
