On Tue, Mar 16, 2021 at 04:42PM +0000, Luis Henriques wrote:
> Hi!
>
> This is probably a known issue, but just in case: looks like it's not
> possible to use kmemleak when kfence is enabled:
Thanks for spotting this.
> [ 0.272136] kmemleak: Cannot insert 0xffff888236e02f00 into the object search tree (overlaps existing)
> [ 0.272136] CPU: 0 PID: 8 Comm: kthreadd Not tainted 5.12.0-rc3+ #92
> [ 0.272136] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a-rebuilt.opensuse.org 04/01/2014
> [ 0.272136] Call Trace:
> [ 0.272136] dump_stack+0x6d/0x89
> [ 0.272136] create_object.isra.0.cold+0x40/0x62
> [ 0.272136] ? process_one_work+0x5a0/0x5a0
> [ 0.272136] ? process_one_work+0x5a0/0x5a0
> [ 0.272136] kmem_cache_alloc_trace+0x110/0x2f0
> [ 0.272136] ? process_one_work+0x5a0/0x5a0
> [ 0.272136] kthread+0x3f/0x150
> [ 0.272136] ? lockdep_hardirqs_on_prepare+0xd4/0x170
> [ 0.272136] ? __kthread_bind_mask+0x60/0x60
> [ 0.272136] ret_from_fork+0x22/0x30
> [ 0.272136] kmemleak: Kernel memory leak detector disabled
> [ 0.272136] kmemleak: Object 0xffff888236e00000 (size 2097152):
> [ 0.272136] kmemleak: comm "swapper", pid 0, jiffies 4294892296
> [ 0.272136] kmemleak: min_count = 0
> [ 0.272136] kmemleak: count = 0
> [ 0.272136] kmemleak: flags = 0x1
> [ 0.272136] kmemleak: checksum = 0
> [ 0.272136] kmemleak: backtrace:
> [ 0.272136] memblock_alloc_internal+0x6d/0xb0
> [ 0.272136] memblock_alloc_try_nid+0x6c/0x8a
> [ 0.272136] kfence_alloc_pool+0x26/0x3f
> [ 0.272136] start_kernel+0x242/0x548
> [ 0.272136] secondary_startup_64_no_verify+0xb0/0xbb
>
> I've tried the hack below but it didn't really helped. Obviously I don't
> really understand what's going on ;-) But I think the reason for this
> patch not working as (I) expected is because kfence is initialised
> *before* kmemleak.
>
> diff --git a/mm/kfence/core.c b/mm/kfence/core.c
> index 3b8ec938470a..b4ffd7695268 100644
> --- a/mm/kfence/core.c
> +++ b/mm/kfence/core.c
> @@ -631,6 +631,9 @@ void __init kfence_alloc_pool(void)
>
> if (!__kfence_pool)
> pr_err("failed to allocate pool\n");
> + kmemleak_no_scan(__kfence_pool);
> }
Can you try the below patch?
Thanks,
-- Marco
------ >8 ------
diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index f7106f28443d..5891019721f6 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -12,6 +12,7 @@
#include <linux/debugfs.h>
#include <linux/kcsan-checks.h>
#include <linux/kfence.h>
+#include <linux/kmemleak.h>
#include <linux/list.h>
#include <linux/lockdep.h>
#include <linux/memblock.h>
@@ -481,6 +482,13 @@ static bool __init kfence_init_pool(void)
addr += 2 * PAGE_SIZE;
}
+ /*
+ * The pool is live and will never be deallocated from this point on;
+ * tell kmemleak this is now free memory, so that later allocations can
+ * correctly be tracked.
+ */
+ kmemleak_free_part_phys(__pa(__kfence_pool), KFENCE_POOL_SIZE);
+
return true;
err:
