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FromJiri Slaby <>
Subject[PATCH 07/16] X86: use ACCESS_ONCE for rlimits
DateWed, 18 Nov 2009 15:51:53 +0100
Make sure compiler won't do weird things with limits. E.g. fetching
them twice may return 2 different values after writable limits are
implemented.

Signed-off-by: Jiri Slaby <jslaby@novell.com>
Cc: James Morris <jmorris@namei.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
---
arch/x86/ia32/ia32_aout.c | 2 +-
arch/x86/mm/mmap.c | 6 ++++--
2 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c
index 2a4d073..239071b 100644
--- a/arch/x86/ia32/ia32_aout.c
+++ b/arch/x86/ia32/ia32_aout.c
@@ -297,7 +297,7 @@ static int load_aout_binary(struct linux_binprm *bprm, struct pt_regs *regs)
* size limits imposed on them by creating programs with large
* arrays in the data or bss.
*/
- rlim = current->signal->rlim[RLIMIT_DATA].rlim_cur;
+ rlim = ACCESS_ONCE(current->signal->rlim[RLIMIT_DATA].rlim_cur);
if (rlim >= RLIM_INFINITY)
rlim = ~0;
if (ex.a_data + ex.a_bss > rlim)
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index c8191de..5578c84 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -71,7 +71,8 @@ static int mmap_is_legacy(void)
if (current->personality & ADDR_COMPAT_LAYOUT)
return 1;

- if (current->signal->rlim[RLIMIT_STACK].rlim_cur == RLIM_INFINITY)
+ if (ACCESS_ONCE(current->signal->rlim[RLIMIT_STACK].rlim_cur)
+ == RLIM_INFINITY)
return 1;

return sysctl_legacy_va_layout;
@@ -96,7 +97,8 @@ static unsigned long mmap_rnd(void)

static unsigned long mmap_base(void)
{
- unsigned long gap = current->signal->rlim[RLIMIT_STACK].rlim_cur;
+ unsigned long gap =
+ ACCESS_ONCE(current->signal->rlim[RLIMIT_STACK].rlim_cur);

if (gap < MIN_GAP)
gap = MIN_GAP;
--
1.6.4.2


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