slub: relax CMPXCHG consistency restrictions
When debug options are enabled, cmpxchg on the page is disabled. This
is because the page must be locked to ensure there are no false
positives when performing consistency checks. Some debug options such
as poisoning and red zoning only act on the object itself. There is no
need to protect other CPUs from modification on only the object. Allow
cmpxchg to happen with poisoning and red zoning are set on a slab.
Credit to Mathias Krause for the original work which inspired this
series
Signed-off-by: Laura Abbott <labbott@fedoraproject.org>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/slub.c b/mm/slub.c
index 9cde663..c2a227d 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -164,6 +164,14 @@
SLAB_POISON | SLAB_STORE_USER)
/*
+ * These debug flags cannot use CMPXCHG because there might be consistency
+ * issues when checking or reading debug information
+ */
+#define SLAB_NO_CMPXCHG (SLAB_CONSISTENCY_CHECKS | SLAB_STORE_USER | \
+ SLAB_TRACE)
+
+
+/*
* Debugging flags that require metadata to be stored in the slab. These get
* disabled when slub_debug=O is used and a cache's min order increases with
* metadata.
@@ -3338,7 +3346,7 @@
#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
- if (system_has_cmpxchg_double() && (s->flags & SLAB_DEBUG_FLAGS) == 0)
+ if (system_has_cmpxchg_double() && (s->flags & SLAB_NO_CMPXCHG) == 0)
/* Enable fast mode */
s->flags |= __CMPXCHG_DOUBLE;
#endif
@@ -4846,7 +4854,6 @@
s->flags &= ~SLAB_RED_ZONE;
if (buf[0] == '1') {
- s->flags &= ~__CMPXCHG_DOUBLE;
s->flags |= SLAB_RED_ZONE;
}
calculate_sizes(s, -1);
@@ -4867,7 +4874,6 @@
s->flags &= ~SLAB_POISON;
if (buf[0] == '1') {
- s->flags &= ~__CMPXCHG_DOUBLE;
s->flags |= SLAB_POISON;
}
calculate_sizes(s, -1);
