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Commit d77a117e authored by Dan Williams's avatar Dan Williams Committed by Linus Torvalds
Browse files

list: kill list_force_poison() 



Given we have uninitialized list_heads being passed to list_add() it
will always be the case that those uninitialized values randomly trigger
the poison value.  Especially since a list_add() operation will seed the
stack with the poison value for later stack allocations to trip over.

For example, see these two false positive reports:

  list_add attempted on force-poisoned entry
  WARNING: at lib/list_debug.c:34
  [..]
  NIP [c00000000043c390] __list_add+0xb0/0x150
  LR [c00000000043c38c] __list_add+0xac/0x150
  Call Trace:
    __list_add+0xac/0x150 (unreliable)
    __down+0x4c/0xf8
    down+0x68/0x70
    xfs_buf_lock+0x4c/0x150 [xfs]

  list_add attempted on force-poisoned entry(0000000000000500),
   new->next == d0000000059ecdb0, new->prev == 0000000000000500
  WARNING: at lib/list_debug.c:33
  [..]
  NIP [c00000000042db78] __list_add+0xa8/0x140
  LR [c00000000042db74] __list_add+0xa4/0x140
  Call Trace:
    __list_add+0xa4/0x140 (unreliable)
    rwsem_down_read_failed+0x6c/0x1a0
    down_read+0x58/0x60
    xfs_log_commit_cil+0x7c/0x600 [xfs]

Fixes: commit 5c2c2587 ("mm, dax, pmem: introduce {get|put}_dev_pagemap() for dax-gup")
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Reported-by: default avatarEryu Guan <eguan@redhat.com>
Tested-by: default avatarEryu Guan <eguan@redhat.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 06b241f3

include/linux/list.h

+0 −11
Original line number Diff line number Diff line
@@ -113,17 +113,6 @@ extern void __list_del_entry(struct list_head *entry); 
extern void list_del(struct list_head *entry);

#endif



#ifdef CONFIG_DEBUG_LIST

/*

 * See devm_memremap_pages() which wants DEBUG_LIST=y to assert if one

 * of the pages it allocates is ever passed to list_add()

 */

extern void list_force_poison(struct list_head *entry);

#else

/* fallback to the less strict LIST_POISON* definitions */

#define list_force_poison list_del

#endif



/**

 * list_replace - replace old entry by new one

 * @old : the element to be replaced

kernel/memremap.c

+7 −2
Original line number Diff line number Diff line
@@ -351,8 +351,13 @@ void *devm_memremap_pages(struct device *dev, struct resource *res, 
	for_each_device_pfn(pfn, page_map) {

		struct page *page = pfn_to_page(pfn);



		/* ZONE_DEVICE pages must never appear on a slab lru */

		list_force_poison(&page->lru);

		/*

		 * ZONE_DEVICE pages union ->lru with a ->pgmap back

		 * pointer.  It is a bug if a ZONE_DEVICE page is ever

		 * freed or placed on a driver-private list.  Seed the

		 * storage with LIST_POISON* values.

		 */

		list_del(&page->lru);

		page->pgmap = pgmap;

	}

	devres_add(dev, page_map);

lib/list_debug.c

+0 −9
Original line number Diff line number Diff line
@@ -12,13 +12,6 @@ 
#include <linux/kernel.h>

#include <linux/rculist.h>



static struct list_head force_poison;

void list_force_poison(struct list_head *entry)

{

	entry->next = &force_poison;

	entry->prev = &force_poison;

}



/*

 * Insert a new entry between two known consecutive entries.

 *
@@ -30,8 +23,6 @@ void __list_add(struct list_head *new, 
			      struct list_head *prev,

			      struct list_head *next)

{

	WARN(new->next == &force_poison || new->prev == &force_poison,

		"list_add attempted on force-poisoned entry\n");

	WARN(next->prev != prev,

		"list_add corruption. next->prev should be "

		"prev (%p), but was %p. (next=%p).\n",