kasan: prevent cpu_quarantine corruption when CPU offline and cache shrink occur...

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@linux-foundation.org: add comment, per Zqiang]

Link: https://lkml.kernel.org/r/20220414025925.2423818-1-qiang1.zhang@intel.com
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
index 08291ed33e93af757e436b8e2efbe626d50c1f79..0a9def8ce5e8b6d68873231f418b85ac96b40bfa 100644 (file)
--- a/mm/kasan/quarantine.c
+++ b/mm/kasan/quarantine.c
@@ -315,6 +315,13 @@ static void per_cpu_remove_cache(void *arg)
        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);
 }