From: Andrey Ryabinin a.ryabinin@samsung.com
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 (cherry picked from commit a79316c6178ca419e35feef47d47f50b4e0ee9f2) Signed-off-by: Alex Shi alex.shi@linaro.org --- mm/slub.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+)
diff --git a/mm/slub.c b/mm/slub.c index dcc2059..d569522 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -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> @@ -468,12 +469,30 @@ 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)