Re: [PATCH 5.19.y] Revert "mm: kfence: apply kmemleak_ignore_phys on early allocated pool"

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Tue, Aug 16, 2022 at 06:42:46PM +0200, Marco Elver wrote:
> On Tue, 16 Aug 2022 at 18:37, Marco Elver <elver@google.com> wrote:
> >
> > This reverts commit 07313a2b29ed1079eaa7722624544b97b3ead84b.
> >
> > Commit 0c24e061196c21d5 ("mm: kmemleak: add rbtree and store physical
> > address for objects allocated with PA") is not yet in 5.19 (but appears
> > in 6.0). Without 0c24e061196c21d5, kmemleak still stores phys objects
> > and non-phys objects in the same tree, and ignoring (instead of freeing)
> > will cause insertions into the kmemleak object tree by the slab
> > post-alloc hook to conflict with the pool object (see comment).
> >
> > Reports such as the following would appear on boot, and effectively
> > disable kmemleak:
> >
> >  | kmemleak: Cannot insert 0xffffff806e24f000 into the object search tree (overlaps existing)
> >  | CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.19.0-v8-0815+ #5
> >  | Hardware name: Raspberry Pi Compute Module 4 Rev 1.0 (DT)
> >  | Call trace:
> >  |  dump_backtrace.part.0+0x1dc/0x1ec
> >  |  show_stack+0x24/0x80
> >  |  dump_stack_lvl+0x8c/0xb8
> >  |  dump_stack+0x1c/0x38
> >  |  create_object.isra.0+0x490/0x4b0
> >  |  kmemleak_alloc+0x3c/0x50
> >  |  kmem_cache_alloc+0x2f8/0x450
> >  |  __proc_create+0x18c/0x400
> >  |  proc_create_reg+0x54/0xd0
> >  |  proc_create_seq_private+0x94/0x120
> >  |  init_mm_internals+0x1d8/0x248
> >  |  kernel_init_freeable+0x188/0x388
> >  |  kernel_init+0x30/0x150
> >  |  ret_from_fork+0x10/0x20
> >  | kmemleak: Kernel memory leak detector disabled
> >  | kmemleak: Object 0xffffff806e24d000 (size 2097152):
> >  | kmemleak:   comm "swapper", pid 0, jiffies 4294892296
> >  | kmemleak:   min_count = -1
> >  | kmemleak:   count = 0
> >  | kmemleak:   flags = 0x5
> >  | kmemleak:   checksum = 0
> >  | kmemleak:   backtrace:
> >  |      kmemleak_alloc_phys+0x94/0xb0
> >  |      memblock_alloc_range_nid+0x1c0/0x20c
> >  |      memblock_alloc_internal+0x88/0x100
> >  |      memblock_alloc_try_nid+0x148/0x1ac
> >  |      kfence_alloc_pool+0x44/0x6c
> >  |      mm_init+0x28/0x98
> >  |      start_kernel+0x178/0x3e8
> >  |      __primary_switched+0xc4/0xcc
> >
> > Reported-by: Max Schulze <max.schulze@online.de>
> > Signed-off-by: Marco Elver <elver@google.com>
> 
> The discussion is:
> 
> Link: https://lore.kernel.org/all/b33b33bc-2d06-1bcd-2df7-43678962b728@online.de/
> 
> > ---
> >  mm/kfence/core.c | 18 +++++++++---------
> >  1 file changed, 9 insertions(+), 9 deletions(-)
> >
> > diff --git a/mm/kfence/core.c b/mm/kfence/core.c
> > index 6aff49f6b79e..4b5e5a3d3a63 100644
> > --- a/mm/kfence/core.c
> > +++ b/mm/kfence/core.c
> > @@ -603,6 +603,14 @@ static unsigned long kfence_init_pool(void)
> >                 addr += 2 * PAGE_SIZE;
> >         }
> >
> > +       /*
> > +        * The pool is live and will never be deallocated from this point on.
> > +        * Remove the pool object from the kmemleak object tree, as it would
> > +        * otherwise overlap with allocations returned by kfence_alloc(), which
> > +        * are registered with kmemleak through the slab post-alloc hook.
> > +        */
> > +       kmemleak_free(__kfence_pool);
> > +
> >         return 0;
> >  }
> >
> > @@ -615,16 +623,8 @@ static bool __init kfence_init_pool_early(void)
> >
> >         addr = kfence_init_pool();
> >
> > -       if (!addr) {
> > -               /*
> > -                * The pool is live and will never be deallocated from this point on.
> > -                * Ignore the pool object from the kmemleak phys object tree, as it would
> > -                * otherwise overlap with allocations returned by kfence_alloc(), which
> > -                * are registered with kmemleak through the slab post-alloc hook.
> > -                */
> > -               kmemleak_ignore_phys(__pa(__kfence_pool));
> > +       if (!addr)
> >                 return true;
> > -       }
> >
> >         /*
> >          * Only release unprotected pages, and do not try to go back and change
> > --
> > 2.37.1.595.g718a3a8f04-goog
> >

Now queued up, thanks.

greg k-h