kernel-ark/include/linux/poison.h
Mel Gorman 23be7468e8 hugetlb: fix infinite loop in get_futex_key() when backed by huge pages
If a futex key happens to be located within a huge page mapped
MAP_PRIVATE, get_futex_key() can go into an infinite loop waiting for a
page->mapping that will never exist.

See https://bugzilla.redhat.com/show_bug.cgi?id=552257 for more details
about the problem.

This patch makes page->mapping a poisoned value that includes
PAGE_MAPPING_ANON mapped MAP_PRIVATE.  This is enough for futex to
continue but because of PAGE_MAPPING_ANON, the poisoned value is not
dereferenced or used by futex.  No other part of the VM should be
dereferencing the page->mapping of a hugetlbfs page as its page cache is
not on the LRU.

This patch fixes the problem with the test case described in the bugzilla.

[akpm@linux-foundation.org: mel cant spel]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Darren Hart <darren@dvhart.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-04-24 11:31:25 -07:00

99 lines
2.9 KiB
C

#ifndef _LINUX_POISON_H
#define _LINUX_POISON_H
/********** include/linux/list.h **********/
/*
* Architectures might want to move the poison pointer offset
* into some well-recognized area such as 0xdead000000000000,
* that is also not mappable by user-space exploits:
*/
#ifdef CONFIG_ILLEGAL_POINTER_VALUE
# define POISON_POINTER_DELTA _AC(CONFIG_ILLEGAL_POINTER_VALUE, UL)
#else
# define POISON_POINTER_DELTA 0
#endif
/*
* These are non-NULL pointers that will result in page faults
* under normal circumstances, used to verify that nobody uses
* non-initialized list entries.
*/
#define LIST_POISON1 ((void *) 0x00100100 + POISON_POINTER_DELTA)
#define LIST_POISON2 ((void *) 0x00200200 + POISON_POINTER_DELTA)
/********** include/linux/timer.h **********/
/*
* Magic number "tsta" to indicate a static timer initializer
* for the object debugging code.
*/
#define TIMER_ENTRY_STATIC ((void *) 0x74737461)
/********** mm/debug-pagealloc.c **********/
#define PAGE_POISON 0xaa
/********** mm/slab.c **********/
/*
* Magic nums for obj red zoning.
* Placed in the first word before and the first word after an obj.
*/
#define RED_INACTIVE 0x09F911029D74E35BULL /* when obj is inactive */
#define RED_ACTIVE 0xD84156C5635688C0ULL /* when obj is active */
#define SLUB_RED_INACTIVE 0xbb
#define SLUB_RED_ACTIVE 0xcc
/* ...and for poisoning */
#define POISON_INUSE 0x5a /* for use-uninitialised poisoning */
#define POISON_FREE 0x6b /* for use-after-free poisoning */
#define POISON_END 0xa5 /* end-byte of poisoning */
/********** mm/hugetlb.c **********/
/*
* Private mappings of hugetlb pages use this poisoned value for
* page->mapping. The core VM should not be doing anything with this mapping
* but futex requires the existence of some page->mapping value even though it
* is unused if PAGE_MAPPING_ANON is set.
*/
#define HUGETLB_POISON ((void *)(0x00300300 + POISON_POINTER_DELTA + PAGE_MAPPING_ANON))
/********** arch/$ARCH/mm/init.c **********/
#define POISON_FREE_INITMEM 0xcc
/********** arch/ia64/hp/common/sba_iommu.c **********/
/*
* arch/ia64/hp/common/sba_iommu.c uses a 16-byte poison string with a
* value of "SBAIOMMU POISON\0" for spill-over poisoning.
*/
/********** fs/jbd/journal.c **********/
#define JBD_POISON_FREE 0x5b
#define JBD2_POISON_FREE 0x5c
/********** drivers/base/dmapool.c **********/
#define POOL_POISON_FREED 0xa7 /* !inuse */
#define POOL_POISON_ALLOCATED 0xa9 /* !initted */
/********** drivers/atm/ **********/
#define ATM_POISON_FREE 0x12
#define ATM_POISON 0xdeadbeef
/********** net/ **********/
#define NEIGHBOR_DEAD 0xdeadbeef
#define NETFILTER_LINK_POISON 0xdead57ac
/********** kernel/mutexes **********/
#define MUTEX_DEBUG_INIT 0x11
#define MUTEX_DEBUG_FREE 0x22
/********** lib/flex_array.c **********/
#define FLEX_ARRAY_FREE 0x6c /* for use-after-free poisoning */
/********** security/ **********/
#define KEY_DESTROY 0xbd
/********** sound/oss/ **********/
#define OSS_POISON_FREE 0xAB
#endif