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authorImran Khan <imran.f.khan@oracle.com>2022-08-15 05:53:53 +1000
committerAndrew Morton <akpm@linux-foundation.org>2022-09-11 20:25:52 -0700
commitb84e04f1baeebe6872b22a027cfc558621e842d4 (patch)
tree144f0b2e5357717a15231f00013e6cabbc2c8b99 /mm/kfence
parent831568214883e0a9940f776771343420306d2341 (diff)
kfence: add sysfs interface to disable kfence for selected slabs.
By default kfence allocation can happen for any slab object, whose size is up to PAGE_SIZE, as long as that allocation is the first allocation after expiration of kfence sample interval. But in certain debugging scenarios we may be interested in debugging corruptions involving some specific slub objects like dentry or ext4_* etc. In such cases limiting kfence for allocations involving only specific slub objects will increase the probablity of catching the issue since kfence pool will not be consumed by other slab objects. This patch introduces a sysfs interface '/sys/kernel/slab/<name>/skip_kfence' to disable kfence for specific slabs. Having the interface work in this way does not impact current/default behavior of kfence and allows us to use kfence for specific slabs (when needed) as well. The decision to skip/use kfence is taken depending on whether kmem_cache.flags has (newly introduced) SLAB_SKIP_KFENCE flag set or not. Link: https://lkml.kernel.org/r/20220814195353.2540848-1-imran.f.khan@oracle.com Signed-off-by: Imran Khan <imran.f.khan@oracle.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Marco Elver <elver@google.com> Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Roman Gushchin <roman.gushchin@linux.dev> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/kfence')
-rw-r--r--mm/kfence/core.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index c252081b11df..8c08ae2101d7 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -1003,6 +1003,13 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
return NULL;
}
+ /*
+ * Skip allocations for this slab, if KFENCE has been disabled for
+ * this slab.
+ */
+ if (s->flags & SLAB_SKIP_KFENCE)
+ return NULL;
+
if (atomic_inc_return(&kfence_allocation_gate) > 1)
return NULL;
#ifdef CONFIG_KFENCE_STATIC_KEYS