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

[Marco Elver]

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@xxxxxxxxx>
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
---
 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