mm: slub: introduce metadata_access_enable()/metadata_access_disable() (a79316c6) · Commits · 戴 / test

It's ok for slub to access memory that marked by kasan as inaccessible (object's metadata). Kasan shouldn't print report in that case because these accesses are valid. Disabling instrumentation of slub.c code is not enough to achieve this because slub passes pointer to object's metadata into external functions like memchr_inv(). We don't want to disable instrumentation for memchr_inv() because this is quite generic function, and we don't want to miss bugs. metadata_access_enable/metadata_access_disable used to tell KASan where accesses to metadata starts/end, so we could temporarily disable KASan reports. Signed-off-by:

Andrey Ryabinin <a.ryabinin@samsung.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Konstantin Serebryany <kcc@google.com> Cc: Dmitry Chernenkov <dmitryc@google.com> Signed-off-by:

Andrey Konovalov <adech.fo@gmail.com> Cc: Yuri Gribov <tetra2005@gmail.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Christoph Lameter <cl@linux.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/slub.c

+25 −0

Original line number	Diff line number	Diff line
		@@ -20,6 +20,7 @@
		#include <linux/proc_fs.h>
		#include <linux/notifier.h>
		#include <linux/seq_file.h>
		#include <linux/kasan.h>
		#include <linux/kmemcheck.h>
		#include <linux/cpu.h>
		#include <linux/cpuset.h>
		@@ -467,13 +468,31 @@ static int slub_debug;
		static char *slub_debug_slabs;
		static int disable_higher_order_debug;

		/*
		* slub is about to manipulate internal object metadata. This memory lies
		* outside the range of the allocated object, so accessing it would normally
		* be reported by kasan as a bounds error. metadata_access_enable() is used
		* to tell kasan that these accesses are OK.
		*/
		static inline void metadata_access_enable(void)
		{
		kasan_disable_current();
		}

		static inline void metadata_access_disable(void)
		{
		kasan_enable_current();
		}

		/*
		* Object debugging
		*/
		static void print_section(char text, u8 addr, unsigned int length)
		{
		metadata_access_enable();
		print_hex_dump(KERN_ERR, text, DUMP_PREFIX_ADDRESS, 16, 1, addr,
		length, 1);
		metadata_access_disable();
		}

		static struct track get_track(struct kmem_cache s, void *object,
		@@ -503,7 +522,9 @@ static void set_track(struct kmem_cache s, void object,
		trace.max_entries = TRACK_ADDRS_COUNT;
		trace.entries = p->addrs;
		trace.skip = 3;
		metadata_access_enable();
		save_stack_trace(&trace);
		metadata_access_disable();

		/* See rant in lockdep.c */
		if (trace.nr_entries != 0 &&
		@@ -677,7 +698,9 @@ static int check_bytes_and_report(struct kmem_cache s, struct page page,
		u8 *fault;
		u8 *end;

		metadata_access_enable();
		fault = memchr_inv(start, value, bytes);
		metadata_access_disable();
		if (!fault)
		return 1;

		@@ -770,7 +793,9 @@ static int slab_pad_check(struct kmem_cache s, struct page page)
		if (!remainder)
		return 1;

		metadata_access_enable();
		fault = memchr_inv(end - remainder, POISON_INUSE, remainder);
		metadata_access_disable();
		if (!fault)
		return 1;
		while (end > fault && end[-1] == POISON_INUSE)

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