[PATCH 07/16] X86: use ACCESS_ONCE for rlimits

[Jiri Slaby]

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@xxxxxxxxxx>
Cc: James Morris <jmorris@xxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: x86@xxxxxxxxxx
---
 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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