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list: kill list_force_poison()

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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 5c2c2587b1 ("mm, dax, pmem: introduce {get|put}_dev_pagemap() for dax-gup")
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Eryu Guan <eguan@redhat.com>
Tested-by: Eryu Guan <eguan@redhat.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Dan Williams 2016-03-09 14:08:10 -08:00 committed by Linus Torvalds
parent 06b241f32c
commit d77a117e68
3 changed files with 7 additions and 22 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

11
include/linux/list.h
View file

@ -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

9
kernel/memremap.c
View file

@ -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);

9
lib/list_debug.c
View file

@ -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",