linux-kernel - [PATCH 5.13 197/223] kfence: skip all GFP

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Message-Id: <20210726153852.637867703@linuxfoundation.org>
Date:   Mon, 26 Jul 2021 17:39:49 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Souptick Joarder <jrdr.linux@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.13 197/223] kfence: skip all GFP_ZONEMASK allocations

From: Alexander Potapenko <glider@...gle.com>

commit 236e9f1538523d3d380dda1cc99571d587058f37 upstream.

Allocation requests outside ZONE_NORMAL (MOVABLE, HIGHMEM or DMA) cannot
be fulfilled by KFENCE, because KFENCE memory pool is located in a zone
different from the requested one.

Because callers of kmem_cache_alloc() may actually rely on the
allocation to reside in the requested zone (e.g.  memory allocations
done with __GFP_DMA must be DMAable), skip all allocations done with
GFP_ZONEMASK and/or respective SLAB flags (SLAB_CACHE_DMA and
SLAB_CACHE_DMA32).

Link: https://lkml.kernel.org/r/20210714092222.1890268-2-glider@google.com
Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")
Signed-off-by: Alexander Potapenko <glider@...gle.com>
Reviewed-by: Marco Elver <elver@...gle.com>
Acked-by: Souptick Joarder <jrdr.linux@...il.com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Souptick Joarder <jrdr.linux@...il.com>
Cc: <stable@...r.kernel.org>	[5.12+]
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 mm/kfence/core.c |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -741,6 +741,15 @@ void *__kfence_alloc(struct kmem_cache *
 		return NULL;
 
 	/*
+	 * Skip allocations from non-default zones, including DMA. We cannot
+	 * guarantee that pages in the KFENCE pool will have the requested
+	 * properties (e.g. reside in DMAable memory).
+	 */
+	if ((flags & GFP_ZONEMASK) ||
+	    (s->flags & (SLAB_CACHE_DMA | SLAB_CACHE_DMA32)))
+		return NULL;
+
+	/*
 	 * allocation_gate only needs to become non-zero, so it doesn't make
 	 * sense to continue writing to it and pay the associated contention
 	 * cost, in case we have a large number of concurrent allocations.