Messages in this thread Patch in this message | | | From | Roger Pau Monne <> | Subject | [PATCH] hvc/xen: lock console list traversal | Date | Tue, 29 Nov 2022 15:31:37 +0100 |
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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.pau@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
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