The patch titled
Subject: powerpc,mmap: properly account for stack randomization in mmap_base
has been added to the -mm tree. Its filename is
powerpcmmap-properly-account-for-stack-randomization-in-mmap_base.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/powerpcmmap-properly-account-for-stack-randomization-in-mmap_base.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/powerpcmmap-properly-account-for-stack-randomization-in-mmap_base.patch
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------------------------------------------------------
From: Rik van Riel <riel@xxxxxxxxxx>
Subject: powerpc,mmap: properly account for stack randomization in mmap_base
When RLIMIT_STACK is, for example, 256MB, the current code results in a
gap between the top of the task and mmap_base of 256MB, failing to take
into account the amount by which the stack address was randomized. In
other words, the stack gets less than RLIMIT_STACK space.
Ensure that the gap between the stack and mmap_base always takes stack
randomization and the stack guard gap into account.
Inspired by Daniel Micay's linux-hardened tree.
Link: http://lkml.kernel.org/r/20170622200033.25714-4-riel@xxxxxxxxxx
Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
Reported-by: Florian Weimer <fweimer@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Daniel Micay <danielmicay@xxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/mm/mmap.c | 28 +++++++++++++++++++---------
1 file changed, 19 insertions(+), 9 deletions(-)
diff -puN arch/powerpc/mm/mmap.c~powerpcmmap-properly-account-for-stack-randomization-in-mmap_base arch/powerpc/mm/mmap.c
--- a/arch/powerpc/mm/mmap.c~powerpcmmap-properly-account-for-stack-randomization-in-mmap_base
+++ a/arch/powerpc/mm/mmap.c
@@ -34,16 +34,9 @@
/*
* Top of mmap area (just below the process stack).
*
- * Leave at least a ~128 MB hole on 32bit applications.
- *
- * On 64bit applications we randomise the stack by 1GB so we need to
- * space our mmap start address by a further 1GB, otherwise there is a
- * chance the mmap area will end up closer to the stack than our ulimit
- * requires.
+ * Leave at least a ~128 MB hole.
*/
-#define MIN_GAP32 (128*1024*1024)
-#define MIN_GAP64 ((128 + 1024)*1024*1024UL)
-#define MIN_GAP ((is_32bit_task()) ? MIN_GAP32 : MIN_GAP64)
+#define MIN_GAP (128*1024*1024)
#define MAX_GAP (TASK_SIZE/6*5)
static inline int mmap_is_legacy(void)
@@ -71,9 +64,26 @@ unsigned long arch_mmap_rnd(void)
return rnd << PAGE_SHIFT;
}
+static inline unsigned long stack_maxrandom_size(void)
+{
+ if (!(current->flags & PF_RANDOMIZE))
+ return 0;
+
+ /* 8MB for 32bit, 1GB for 64bit */
+ if (is_32bit_task())
+ return (1<<23);
+ else
+ return (1<<30);
+}
+
static inline unsigned long mmap_base(unsigned long rnd)
{
unsigned long gap = rlimit(RLIMIT_STACK);
+ unsigned long pad = stack_maxrandom_size() + stack_guard_gap;
+
+ /* Values close to RLIM_INFINITY can overflow. */
+ if (gap + pad > gap)
+ gap += pad;
if (gap < MIN_GAP)
gap = MIN_GAP;
_
Patches currently in -mm which might be from riel@xxxxxxxxxx are
randomstackprotect-introduce-get_random_canary-function.patch
forkrandom-use-get_random_canary-to-set-tsk-stack_canary.patch
x86-ascii-armor-the-x86_64-boot-init-stack-canary.patch
arm64-ascii-armor-the-arm64-boot-init-stack-canary.patch
sh64-ascii-armor-the-sh64-boot-init-stack-canary.patch
x86-mmap-properly-account-for-stack-randomization-in-mmap_base.patch
arm64-mmap-properly-account-for-stack-randomization-in-mmap_base.patch
powerpcmmap-properly-account-for-stack-randomization-in-mmap_base.patch
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