On Tue, Mar 16, 2021 at 06:30:00PM +0100, Marco Elver wrote:
> 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?
Yep, that seems to fix the issue. Feel free to add my Tested-by. Thanks!
Cheers,
--
Luís
>
> 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:
