[PATCH 5.15 017/132] mm/kfence: reset PG_slab and memcg_data before freeing __kfence_pool

Greg Kroah-Hartman
2022-05-23T17:39:02Z

From: Hyeonggon Yoo <42.hyeyoo@gmail.com>

commit 2839b0999c20c9f6bf353849c69370e121e2fa1a upstream.

When kfence fails to initialize kfence pool, it frees the pool. But it
does not reset memcg_data and PG_slab flag.

Below is a BUG because of this. Let's fix it by resetting memcg_data
and PG_slab flag before free.

[ 0.089149] BUG: Bad page state in process swapper/0 pfn:3d8e06
[ 0.089149] page:ffffea46cf638180 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3d8e06
[ 0.089150] memcg:ffffffff94a475d1
[ 0.089150] flags: 0x17ffffc0000200(slab|node=0|zone=2|lastcpupid=0x1fffff)
[ 0.089151] raw: 0017ffffc0000200 ffffea46cf638188 ffffea46cf638188 0000000000000000
[ 0.089152] raw: 0000000000000000 0000000000000000 00000000ffffffff ffffffff94a475d1
[ 0.089152] page dumped because: page still charged to cgroup
[ 0.089153] Modules linked in:
[ 0.089153] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G B W 5.18.0-rc1+ #965
[ 0.089154] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
[ 0.089154] Call Trace:
[ 0.089155] <TASK>
[ 0.089155] dump_stack_lvl+0x49/0x5f
[ 0.089157] dump_stack+0x10/0x12
[ 0.089158] bad_page.cold+0x63/0x94
[ 0.089159] check_free_page_bad+0x66/0x70
[ 0.089160] __free_pages_ok+0x423/0x530
[ 0.089161] __free_pages_core+0x8e/0xa0
[ 0.089162] memblock_free_pages+0x10/0x12
[ 0.089164] memblock_free_late+0x8f/0xb9
[ 0.089165] kfence_init+0x68/0x92
[ 0.089166] start_kernel+0x789/0x992
[ 0.089167] x86_64_start_reservations+0x24/0x26
[ 0.089168] x86_64_start_kernel+0xa9/0xaf
[ 0.089170] secondary_startup_64_no_verify+0xd5/0xdb
[ 0.089171] </TASK>

Link: https://lkml.kernel.org/r/YnPG3pQrqfcgOlVa@hyeyoo
Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")
Fixes: 8f0b36497303 ("mm: kfence: fix objcgs vector allocation")
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
[42.hyeyoo@gmail.com: backport - use struct page]
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
mm/kfence/core.c | 11 +++++++++++
1 file changed, 11 insertions(+)

--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -510,6 +510,7 @@ static bool __init kfence_init_pool(void
unsigned long addr = (unsigned long)__kfence_pool;
struct page *pages;
int i;
+ char *p;

if (!__kfence_pool)
return false;
@@ -592,6 +593,16 @@ err:
* fails for the first page, and therefore expect addr==__kfence_pool in
* most failure cases.
*/
+ for (p = (char *)addr; p < __kfence_pool + KFENCE_POOL_SIZE; p += PAGE_SIZE) {
+ struct page *page = virt_to_page(p);
+
+ if (!PageSlab(page))
+ continue;
+#ifdef CONFIG_MEMCG
+ page->memcg_data = 0;
+#endif
+ __ClearPageSlab(page);
+ }
memblock_free_late(__pa(addr), KFENCE_POOL_SIZE - (addr - (unsigned long)__kfence_pool));
__kfence_pool = NULL;
return false;