On 2023/3/21 12:14, Peng Zhang wrote:
在 2023/3/20 11:00, Muchun Song 写道:
It does not reset PG_slab and memcg_data when KFENCE fails to initialize
kfence pool at runtime. It is reporting a "Bad page state" message when
kfence pool is freed to buddy. The checking of whether it is a compound
head page seems unnecessary sicne we already guarantee this when
allocating
kfence pool, removing the check to simplify the code.
Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")
Fixes: 8f0b36497303 ("mm: kfence: fix objcgs vector allocation")
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
mm/kfence/core.c | 30 +++++++++++++++---------------
1 file changed, 15 insertions(+), 15 deletions(-)
diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 79c94ee55f97..d66092dd187c 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -561,10 +561,6 @@ static unsigned long kfence_init_pool(void)
if (!i || (i % 2))
continue;
- /* Verify we do not have a compound head page. */
- if (WARN_ON(compound_head(&pages[i]) != &pages[i]))
- return addr;
-
__folio_set_slab(slab_folio(slab));
#ifdef CONFIG_MEMCG
slab->memcg_data = (unsigned long)&kfence_metadata[i / 2 -
1].objcg |
@@ -597,12 +593,26 @@ static unsigned long kfence_init_pool(void)
/* Protect the right redzone. */
if (unlikely(!kfence_protect(addr + PAGE_SIZE)))
- return addr;
+ goto reset_slab;
addr += 2 * PAGE_SIZE;
}
return 0;
+
+reset_slab:
+ for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) {
+ struct slab *slab = page_slab(&pages[i]);
+
+ if (!i || (i % 2))
+ continue;
+#ifdef CONFIG_MEMCG
+ slab->memcg_data = 0;
+#endif
+ __folio_clear_slab(slab_folio(slab));
+ }
Can this loop be simplified to this?
for (i = 2; i < KFENCE_POOL_SIZE / PAGE_SIZE; i+=2) {
struct slab *slab = page_slab(&pages[i]);
#ifdef CONFIG_MEMCG
slab->memcg_data = 0;
#endif
__folio_clear_slab(slab_folio(slab));
}
It's a good simplification. The loop setting Pg_slab before this
also can be simplified in the same way. However, I choose a
consistent way to fix this bug. I'd like to send a separate
simplification patch to simplify both two loops instead of
in a bugfix patch.
Thanks.
