| Message ID | 20190114233405.67843-1-cai@lca.pw (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] page_poison: play nicely with KASAN | expand |
On 1/15/19 2:34 AM, Qian Cai wrote: > KASAN does not play well with the page poisoning > (CONFIG_PAGE_POISONING). It triggers false positives in the allocation > path, > > BUG: KASAN: use-after-free in memchr_inv+0x2ea/0x330 > Read of size 8 at addr ffff88881f800000 by task swapper/0 > CPU: 0 PID: 0 Comm: swapper Not tainted 5.0.0-rc1+ #54 > Call Trace: > dump_stack+0xe0/0x19a > print_address_description.cold.2+0x9/0x28b > kasan_report.cold.3+0x7a/0xb5 > __asan_report_load8_noabort+0x19/0x20 > memchr_inv+0x2ea/0x330 > kernel_poison_pages+0x103/0x3d5 > get_page_from_freelist+0x15e7/0x4d90 > > because KASAN has not yet unpoisoned the shadow page for allocation > before it checks memchr_inv() but only found a stale poison pattern. > > Also, false positives in free path, > > BUG: KASAN: slab-out-of-bounds in kernel_poison_pages+0x29e/0x3d5 > Write of size 4096 at addr ffff8888112cc000 by task swapper/0/1 > CPU: 5 PID: 1 Comm: swapper/0 Not tainted 5.0.0-rc1+ #55 > Call Trace: > dump_stack+0xe0/0x19a > print_address_description.cold.2+0x9/0x28b > kasan_report.cold.3+0x7a/0xb5 > check_memory_region+0x22d/0x250 > memset+0x28/0x40 > kernel_poison_pages+0x29e/0x3d5 > __free_pages_ok+0x75f/0x13e0 > > due to KASAN adds poisoned redzones around slab objects, but the page > poisoning needs to poison the whole page. > > Signed-off-by: Qian Cai <cai@lca.pw> > --- > Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d295c9bc01a8..906250a9b89c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1945,8 +1945,8 @@ inline void post_alloc_hook(struct page *page, unsigned int order, arch_alloc_page(page, order); kernel_map_pages(page, 1 << order, 1); - kernel_poison_pages(page, 1 << order, 1); kasan_alloc_pages(page, order); + kernel_poison_pages(page, 1 << order, 1); set_page_owner(page, order, gfp_flags); } diff --git a/mm/page_poison.c b/mm/page_poison.c index f0c15e9017c0..21d4f97cb49b 100644 --- a/mm/page_poison.c +++ b/mm/page_poison.c @@ -6,6 +6,7 @@ #include <linux/page_ext.h> #include <linux/poison.h> #include <linux/ratelimit.h> +#include <linux/kasan.h> static bool want_page_poisoning __read_mostly; @@ -40,7 +41,10 @@ static void poison_page(struct page *page) { void *addr = kmap_atomic(page); + /* KASAN still think the page is in-use, so skip it. */ + kasan_disable_current(); memset(addr, PAGE_POISON, PAGE_SIZE); + kasan_enable_current(); kunmap_atomic(addr); }
KASAN does not play well with the page poisoning (CONFIG_PAGE_POISONING). It triggers false positives in the allocation path, BUG: KASAN: use-after-free in memchr_inv+0x2ea/0x330 Read of size 8 at addr ffff88881f800000 by task swapper/0 CPU: 0 PID: 0 Comm: swapper Not tainted 5.0.0-rc1+ #54 Call Trace: dump_stack+0xe0/0x19a print_address_description.cold.2+0x9/0x28b kasan_report.cold.3+0x7a/0xb5 __asan_report_load8_noabort+0x19/0x20 memchr_inv+0x2ea/0x330 kernel_poison_pages+0x103/0x3d5 get_page_from_freelist+0x15e7/0x4d90 because KASAN has not yet unpoisoned the shadow page for allocation before it checks memchr_inv() but only found a stale poison pattern. Also, false positives in free path, BUG: KASAN: slab-out-of-bounds in kernel_poison_pages+0x29e/0x3d5 Write of size 4096 at addr ffff8888112cc000 by task swapper/0/1 CPU: 5 PID: 1 Comm: swapper/0 Not tainted 5.0.0-rc1+ #55 Call Trace: dump_stack+0xe0/0x19a print_address_description.cold.2+0x9/0x28b kasan_report.cold.3+0x7a/0xb5 check_memory_region+0x22d/0x250 memset+0x28/0x40 kernel_poison_pages+0x29e/0x3d5 __free_pages_ok+0x75f/0x13e0 due to KASAN adds poisoned redzones around slab objects, but the page poisoning needs to poison the whole page. Signed-off-by: Qian Cai <cai@lca.pw> --- v2: use kasan_disable/enable_current() instead. mm/page_alloc.c | 2 +- mm/page_poison.c | 4 ++++ 2 files changed, 5 insertions(+), 1 deletion(-)