[PATCH 5.10 108/129] kasan: prevent cpu_quarantine corruption when CPU offline and cache shrink occur at same time

[Greg Kroah-Hartman]

From: Zqiang <qiang1.zhang@xxxxxxxxx>

commit 31fa985b4196f8a66f027672e9bf2b81fea0417c upstream.

kasan_quarantine_remove_cache() is called in kmem_cache_shrink()/
destroy().  The kasan_quarantine_remove_cache() call is protected by
cpuslock in kmem_cache_destroy() to ensure serialization with
kasan_cpu_offline().

However the kasan_quarantine_remove_cache() call is not protected by
cpuslock in kmem_cache_shrink().  When a CPU is going offline and cache
shrink occurs at same time, the cpu_quarantine may be corrupted by
interrupt (per_cpu_remove_cache operation).

So add a cpu_quarantine offline flags check in per_cpu_remove_cache().

[akpm@xxxxxxxxxxxxxxxxxxxx: add comment, per Zqiang]

Link: https://lkml.kernel.org/r/20220414025925.2423818-1-qiang1.zhang@xxxxxxxxx
Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 mm/kasan/quarantine.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/mm/kasan/quarantine.c
+++ b/mm/kasan/quarantine.c
@@ -299,6 +299,13 @@ static void per_cpu_remove_cache(void *a
 	struct qlist_head *q;
 
 	q = this_cpu_ptr(&cpu_quarantine);
+	/*
+	 * Ensure the ordering between the writing to q->offline and
+	 * per_cpu_remove_cache.  Prevent cpu_quarantine from being corrupted
+	 * by interrupt.
+	 */
+	if (READ_ONCE(q->offline))
+		return;
 	qlist_move_cache(q, &to_free, cache);
 	qlist_free_all(&to_free, cache);
 }