| Message ID | 20210304205256.2162309-1-elver@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [mm] kfence, slab: fix cache_alloc_debugcheck_after() for bulk allocations | expand |
On Thu, Mar 4, 2021 at 9:53 PM Marco Elver <elver@google.com> wrote: > > cache_alloc_debugcheck_after() performs checks on an object, including > adjusting the returned pointer. None of this should apply to KFENCE > objects. While for non-bulk allocations, the checks are skipped when we > allocate via KFENCE, for bulk allocations cache_alloc_debugcheck_after() > is called via cache_alloc_debugcheck_after_bulk(). @Andrew, is this code used by anyone? As far as I understand, it cannot be enabled by any config option, so nobody really tests it. If it is still needed, shall we promote #if DEBUGs in slab.c to a separate config option, or maybe this code can be safely removed? Alex
On Thu, 4 Mar 2021 22:05:48 +0100 Alexander Potapenko <glider@google.com> wrote: > On Thu, Mar 4, 2021 at 9:53 PM Marco Elver <elver@google.com> wrote: > > > > cache_alloc_debugcheck_after() performs checks on an object, including > > adjusting the returned pointer. None of this should apply to KFENCE > > objects. While for non-bulk allocations, the checks are skipped when we > > allocate via KFENCE, for bulk allocations cache_alloc_debugcheck_after() > > is called via cache_alloc_debugcheck_after_bulk(). > > @Andrew, is this code used by anyone? > As far as I understand, it cannot be enabled by any config option, so > nobody really tests it. > If it is still needed, shall we promote #if DEBUGs in slab.c to a > separate config option, or maybe this code can be safely removed? It's all used: #ifdef CONFIG_DEBUG_SLAB #define DEBUG 1 #define STATS 1 #define FORCED_DEBUG 1 #else #define DEBUG 0 #define STATS 0 #define FORCED_DEBUG 0 #endif
On Fri, Mar 5, 2021 at 2:31 AM Andrew Morton <akpm@linux-foundation.org> wrote: > > On Thu, 4 Mar 2021 22:05:48 +0100 Alexander Potapenko <glider@google.com> wrote: > > > On Thu, Mar 4, 2021 at 9:53 PM Marco Elver <elver@google.com> wrote: > > > > > > cache_alloc_debugcheck_after() performs checks on an object, including > > > adjusting the returned pointer. None of this should apply to KFENCE > > > objects. While for non-bulk allocations, the checks are skipped when we > > > allocate via KFENCE, for bulk allocations cache_alloc_debugcheck_after() > > > is called via cache_alloc_debugcheck_after_bulk(). > > > > @Andrew, is this code used by anyone? > > As far as I understand, it cannot be enabled by any config option, so > > nobody really tests it. > > If it is still needed, shall we promote #if DEBUGs in slab.c to a > > separate config option, or maybe this code can be safely removed? > > It's all used: Got it, sorry for being too hasty!
diff --git a/mm/slab.c b/mm/slab.c index 51fd424e0d6d..ae651bf540b7 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -2992,7 +2992,7 @@ static void *cache_alloc_debugcheck_after(struct kmem_cache *cachep, gfp_t flags, void *objp, unsigned long caller) { WARN_ON_ONCE(cachep->ctor && (flags & __GFP_ZERO)); - if (!objp) + if (!objp || is_kfence_address(objp)) return objp; if (cachep->flags & SLAB_POISON) { check_poison_obj(cachep, objp);
cache_alloc_debugcheck_after() performs checks on an object, including adjusting the returned pointer. None of this should apply to KFENCE objects. While for non-bulk allocations, the checks are skipped when we allocate via KFENCE, for bulk allocations cache_alloc_debugcheck_after() is called via cache_alloc_debugcheck_after_bulk(). Fix it by skipping cache_alloc_debugcheck_after() for KFENCE objects. Signed-off-by: Marco Elver <elver@google.com> --- mm/slab.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)