[GIT PULL] Additional x86 fixes

From: H. Peter Anvin
Date: Thu Sep 17 2009 - 17:51:16 EST

Hi Linus,

The following changes since commit de55a8958f6e3ef5ce5f0971b80bd44bfcac7cf1:
Linus Torvalds (1):
Merge branch 'for-linus' of git://git.kernel.org/.../bp/bp

are available in the git repository at:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git x86-fixes-for-linus

H. Peter Anvin (1):
Merge branch 'x86/pat' into x86/urgent

Michal Hocko (1):
x86: Increase MIN_GAP to include randomized stack

Suresh Siddha (1):
x86, pat: don't use rb-tree based lookup in reserve_memtype()

Sorry for the merge, but the PAT fix could not be based on the other
patch without a rebase.

-hpa


commit 80938332d8cf652f6b16e0788cf0ca136befe0b5
Author: Michal Hocko <mhocko@xxxxxxx>
Date: Tue Sep 8 11:01:55 2009 +0200

x86: Increase MIN_GAP to include randomized stack

Currently we are not including randomized stack size when calculating
mmap_base address in arch_pick_mmap_layout for topdown case. This might
cause that mmap_base starts in the stack reserved area because stack is
randomized by 1GB for 64b (8MB for 32b) and the minimum gap is 128MB.

If the stack really grows down to mmap_base then we can get silent mmap
region overwrite by the stack values.

Let's include maximum stack randomization size into MIN_GAP which is
used as the low bound for the gap in mmap.

Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
LKML-Reference: <1252400515-6866-1-git-send-email-mhocko@xxxxxxx>
Acked-by: Jiri Kosina <jkosina@xxxxxxx>
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Stable Team <stable@xxxxxxxxxx>

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 83c1bc8..456a304 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -299,6 +299,8 @@ do { \

#ifdef CONFIG_X86_32

+#define STACK_RND_MASK (0x7ff)
+
#define VDSO_HIGH_BASE (__fix_to_virt(FIX_VDSO))

#define ARCH_DLINFO ARCH_DLINFO_IA32(vdso_enabled)
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index 1658296..c8191de 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -29,13 +29,26 @@
#include <linux/random.h>
#include <linux/limits.h>
#include <linux/sched.h>
+#include <asm/elf.h>
+
+static unsigned int stack_maxrandom_size(void)
+{
+ unsigned int max = 0;
+ if ((current->flags & PF_RANDOMIZE) &&
+ !(current->personality & ADDR_NO_RANDOMIZE)) {
+ max = ((-1U) & STACK_RND_MASK) << PAGE_SHIFT;
+ }
+
+ return max;
+}
+

/*
* Top of mmap area (just below the process stack).
*
- * Leave an at least ~128 MB hole.
+ * Leave an at least ~128 MB hole with possible stack randomization.
*/
-#define MIN_GAP (128*1024*1024)
+#define MIN_GAP (128*1024*1024UL + stack_maxrandom_size())
#define MAX_GAP (TASK_SIZE/6*5)

/*
commit dcb73bf402e0d5b28ce925dbbe4dab3b00b21eee
Author: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
Date: Wed Sep 16 14:28:03 2009 -0700

x86, pat: don't use rb-tree based lookup in reserve_memtype()

Recent enhancement of rb-tree based lookup exposed a bug with the lookup
mechanism in the reserve_memtype() which ensures that there are no conflicting
memtype requests for the memory range.

memtype_rb_search() returns an entry which has a start address <= new start
address. And from here we traverse the linear linked list to check if there
any conflicts with the existing mappings. As the rbtree is based on the
start address of the memory range, it is quite possible that we have several
overlapped mappings whose start address is much less than new requested start
but the end is >= new requested end. This results in conflicting memtype
mappings.

Same bug exists with the old code which uses cached_entry from where
we traverse the linear linked list. But the new rb-tree code exposes this
bug fairly easily.

For now, don't use the memtype_rb_search() and always start the search from
the head of linear linked list in reserve_memtype(). Linear linked list
for most of the systems grow's to few 10's of entries(as we track memory type
of RAM pages using struct page). So we should be ok for now.

We still retain the rbtree and use it to speed up free_memtype() which
doesn't have the same bug(as we know what exactly we are searching for
in free_memtype).

Also use list_for_each_entry_from() in free_memtype() so that we start
the search from rb-tree lookup result.

Reported-by: Markus Trippelsdorf <markus@xxxxxxxxxxxxxxx>
Signed-off-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
LKML-Reference: <1253136483.4119.12.camel@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxx>

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index d2a72ab..9b647f6 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -424,17 +424,9 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,

spin_lock(&memtype_lock);

- entry = memtype_rb_search(&memtype_rbroot, new->start);
- if (likely(entry != NULL)) {
- /* To work correctly with list_for_each_entry_continue */
- entry = list_entry(entry->nd.prev, struct memtype, nd);
- } else {
- entry = list_entry(&memtype_list, struct memtype, nd);
- }
-
/* Search for existing mapping that overlaps the current range */
where = NULL;
- list_for_each_entry_continue(entry, &memtype_list, nd) {
+ list_for_each_entry(entry, &memtype_list, nd) {
if (end <= entry->start) {
where = entry->nd.prev;
break;
@@ -532,7 +524,7 @@ int free_memtype(u64 start, u64 end)
* in sorted start address
*/
saved_entry = entry;
- list_for_each_entry(entry, &memtype_list, nd) {
+ list_for_each_entry_from(entry, &memtype_list, nd) {
if (entry->start == start && entry->end == end) {
rb_erase(&entry->rb, &memtype_rbroot);
list_del(&entry->nd);
--
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