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SubjectRe: [PATCH 5/5] kasan, slub: fix conflicts with CONFIG_SLAB_FREELIST_HARDENED
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On 2/11/19 4:59 PM, Andrey Konovalov wrote:
> CONFIG_SLAB_FREELIST_HARDENED hashes freelist pointer with the address
> of the object where the pointer gets stored. With tag based KASAN we don't
> account for that when building freelist, as we call set_freepointer() with
> the first argument untagged. This patch changes the code to properly
> propagate tags throughout the loop.
>
> Reported-by: Qian Cai <cai@lca.pw>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> ---
> mm/slub.c | 20 +++++++-------------
> 1 file changed, 7 insertions(+), 13 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index ce874a5c9ee7..0d32f8d30752 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -303,11 +303,6 @@ static inline void set_freepointer(struct kmem_cache *s, void *object, void *fp)
> __p < (__addr) + (__objects) * (__s)->size; \
> __p += (__s)->size)
>
> -#define for_each_object_idx(__p, __idx, __s, __addr, __objects) \
> - for (__p = fixup_red_left(__s, __addr), __idx = 1; \
> - __idx <= __objects; \
> - __p += (__s)->size, __idx++)
> -
> /* Determine object index from a given position */
> static inline unsigned int slab_index(void *p, struct kmem_cache *s, void *addr)
> {
> @@ -1655,17 +1650,16 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
> shuffle = shuffle_freelist(s, page);
>
> if (!shuffle) {
> - for_each_object_idx(p, idx, s, start, page->objects) {
> - if (likely(idx < page->objects)) {
> - next = p + s->size;
> - next = setup_object(s, page, next);
> - set_freepointer(s, p, next);
> - } else
> - set_freepointer(s, p, NULL);
> - }
> start = fixup_red_left(s, start);
> start = setup_object(s, page, start);
> page->freelist = start;
> + for (idx = 0, p = start; idx < page->objects - 1; idx++) {
> + next = p + s->size;
> + next = setup_object(s, page, next);
> + set_freepointer(s, p, next);
> + p = next;
> + }
> + set_freepointer(s, p, NULL);
> }
>
> page->inuse = page->objects;
>

Well, this one patch does not work here, as it throws endless errors below
during boot. Still need this patch to fix it.

https://marc.info/?l=linux-mm&m=154955366113951&w=2

[ 85.744772] BUG kmemleak_object (Tainted: G B L ): Freepointer
corrupt
[ 85.744776]
-----------------------------------------------------------------------------
[ 85.744776]
[ 85.744788] INFO: Allocated in create_object+0x88/0x9c8 age=2564 cpu=153 pid=1
[ 85.744797] kmem_cache_alloc+0x39c/0x4ec
[ 85.744803] create_object+0x88/0x9c8
[ 85.744811] kmemleak_alloc+0xbc/0x180
[ 85.744818] kmem_cache_alloc+0x3ec/0x4ec
[ 85.744825] acpi_ut_create_generic_state+0x64/0xc4
[ 85.744832] acpi_ut_create_pkg_state+0x24/0x1c8
[ 85.744840] acpi_ut_walk_package_tree+0x268/0x564
[ 85.744848] acpi_ns_init_one_package+0x80/0x114
[ 85.744856] acpi_ns_init_one_object+0x214/0x3d8
[ 85.744862] acpi_ns_walk_namespace+0x288/0x384
[ 85.744869] acpi_walk_namespace+0xac/0xe8
[ 85.744877] acpi_ns_initialize_objects+0x50/0x98
[ 85.744883] acpi_load_tables+0xac/0x120
[ 85.744891] acpi_init+0x128/0x850
[ 85.744898] do_one_initcall+0x3ac/0x8c0
[ 85.744906] kernel_init_freeable+0xcdc/0x1104
[ 85.744916] INFO: Freed in free_object_rcu+0x200/0x228 age=3 cpu=153 pid=0
[ 85.744923] free_object_rcu+0x200/0x228
[ 85.744931] rcu_process_callbacks+0xb00/0x12c0
[ 85.744937] __do_softirq+0x644/0xfd0
[ 85.744944] irq_exit+0x29c/0x370
[ 85.744952] __handle_domain_irq+0xe0/0x1c4
[ 85.744958] gic_handle_irq+0x1c4/0x3b0
[ 85.744964] el1_irq+0xb0/0x140
[ 85.744971] arch_cpu_idle+0x26c/0x594
[ 85.744978] default_idle_call+0x44/0x5c
[ 85.744985] do_idle+0x180/0x260
[ 85.744993] cpu_startup_entry+0x24/0x28
[ 85.745001] secondary_start_kernel+0x36c/0x440
[ 85.745009] INFO: Slab 0x(____ptrval____) objects=91 used=0
fp=0x(____ptrval____) flags=0x17ffffffc000200
[ 85.745015] INFO: Object 0x(____ptrval____) @offset=35296 fp=0x(____ptrval____)

kkkkk4.226750] Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb
bb bb bb ................
[ 84.22[ 84.226765] ORedzone (____ptrptrval____): 5a worker/223:0 Tainted: G
B L 5.0.0-rc6+ #36
[ 84.226790] Hardware name: HPE Apollo 70 /C01_APACHE_MB ,
BIOS L50_5.13_1.0.6 07/10/2018
[ 84.226798] Workqueue: events free_obj_work
[ 84.226802] Call trace:
[ 84.226809] dump_backtrace+0x0/0x450
[ 84.226815] show_stack+0x20/0x2c
[ 84.226822] __dump_stack+0x20/0x28
[ 84.226828] dump_stack+0xa0/0xfc
[ 84.226835] print_trailer+0x1a8/0x1bc
[ 84.226842] object_err+0x40/0x50
[ 84.226848] check_object+0x214/0x2b8
[ 84.226854] __free_slab+0x9c/0x31c
[ 84.226860] discard_slab+0x78/0xa8
[ 84.226866] kmem_cache_free+0x99c/0x9f0
[ 84.226873] free_obj_work+0x92c/0xa44
[ 84.226879] process_one_work+0x894/0x1280
[ 84.226885] worker_thread+0x684/0xa1c
[ 84.226892] kthread+0x2cc/0x2e8
[ 84.226898] ret_from_fork+0x10/0x18
[ 84.229197]

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