diff options
| author | Michel Lespinasse <walken@google.com> | 2011-03-10 18:48:51 -0800 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2011-03-11 12:23:08 +0100 |
| commit | 37a9d912b24f96a0591773e6e6c3642991ae5a70 (patch) | |
| tree | 5c4d5b9a52e2c533269e589115afbd25b6c8534b /arch/s390/lib | |
| parent | 522d7decc0370070448a8c28982c8dfd8970489e (diff) | |
| download | linux-37a9d912b24f96a0591773e6e6c3642991ae5a70.tar.bz2 | |
futex: Sanitize cmpxchg_futex_value_locked API
The cmpxchg_futex_value_locked API was funny in that it returned either
the original, user-exposed futex value OR an error code such as -EFAULT.
This was confusing at best, and could be a source of livelocks in places
that retry the cmpxchg_futex_value_locked after trying to fix the issue
by running fault_in_user_writeable().
This change makes the cmpxchg_futex_value_locked API more similar to the
get_futex_value_locked one, returning an error code and updating the
original value through a reference argument.
Signed-off-by: Michel Lespinasse <walken@google.com>
Acked-by: Chris Metcalf <cmetcalf@tilera.com> [tile]
Acked-by: Tony Luck <tony.luck@intel.com> [ia64]
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michal Simek <monstr@monstr.eu> [microblaze]
Acked-by: David Howells <dhowells@redhat.com> [frv]
Cc: Darren Hart <darren@dvhart.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <20110311024851.GC26122@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/s390/lib')
| -rw-r--r-- | arch/s390/lib/uaccess.h | 4 | ||||
| -rw-r--r-- | arch/s390/lib/uaccess_pt.c | 13 | ||||
| -rw-r--r-- | arch/s390/lib/uaccess_std.c | 6 |
3 files changed, 14 insertions, 9 deletions
diff --git a/arch/s390/lib/uaccess.h b/arch/s390/lib/uaccess.h index 126011df14f1..89a80674e44b 100644 --- a/arch/s390/lib/uaccess.h +++ b/arch/s390/lib/uaccess.h @@ -12,12 +12,12 @@ extern size_t copy_from_user_std(size_t, const void __user *, void *); extern size_t copy_to_user_std(size_t, void __user *, const void *); extern size_t strnlen_user_std(size_t, const char __user *); extern size_t strncpy_from_user_std(size_t, const char __user *, char *); -extern int futex_atomic_cmpxchg_std(int __user *, int, int); +extern int futex_atomic_cmpxchg_std(int *, int __user *, int, int); extern int futex_atomic_op_std(int, int __user *, int, int *); extern size_t copy_from_user_pt(size_t, const void __user *, void *); extern size_t copy_to_user_pt(size_t, void __user *, const void *); extern int futex_atomic_op_pt(int, int __user *, int, int *); -extern int futex_atomic_cmpxchg_pt(int __user *, int, int); +extern int futex_atomic_cmpxchg_pt(int *, int __user *, int, int); #endif /* __ARCH_S390_LIB_UACCESS_H */ diff --git a/arch/s390/lib/uaccess_pt.c b/arch/s390/lib/uaccess_pt.c index 404f2de296dc..b3cebcd52f5c 100644 --- a/arch/s390/lib/uaccess_pt.c +++ b/arch/s390/lib/uaccess_pt.c @@ -354,26 +354,29 @@ int futex_atomic_op_pt(int op, int __user *uaddr, int oparg, int *old) return ret; } -static int __futex_atomic_cmpxchg_pt(int __user *uaddr, int oldval, int newval) +static int __futex_atomic_cmpxchg_pt(int *uval, int __user *uaddr, + int oldval, int newval) { int ret; asm volatile("0: cs %1,%4,0(%5)\n" - "1: lr %0,%1\n" + "1: la %0,0\n" "2:\n" EX_TABLE(0b,2b) EX_TABLE(1b,2b) : "=d" (ret), "+d" (oldval), "=m" (*uaddr) : "0" (-EFAULT), "d" (newval), "a" (uaddr), "m" (*uaddr) : "cc", "memory" ); + *uval = oldval; return ret; } -int futex_atomic_cmpxchg_pt(int __user *uaddr, int oldval, int newval) +int futex_atomic_cmpxchg_pt(int *uval, int __user *uaddr, + int oldval, int newval) { int ret; if (segment_eq(get_fs(), KERNEL_DS)) - return __futex_atomic_cmpxchg_pt(uaddr, oldval, newval); + return __futex_atomic_cmpxchg_pt(uval, uaddr, oldval, newval); spin_lock(¤t->mm->page_table_lock); uaddr = (int __user *) __dat_user_addr((unsigned long) uaddr); if (!uaddr) { @@ -382,7 +385,7 @@ int futex_atomic_cmpxchg_pt(int __user *uaddr, int oldval, int newval) } get_page(virt_to_page(uaddr)); spin_unlock(¤t->mm->page_table_lock); - ret = __futex_atomic_cmpxchg_pt(uaddr, oldval, newval); + ret = __futex_atomic_cmpxchg_pt(uval, uaddr, oldval, newval); put_page(virt_to_page(uaddr)); return ret; } diff --git a/arch/s390/lib/uaccess_std.c b/arch/s390/lib/uaccess_std.c index a6c4f7ed24a4..1d6643c0b95f 100644 --- a/arch/s390/lib/uaccess_std.c +++ b/arch/s390/lib/uaccess_std.c @@ -287,19 +287,21 @@ int futex_atomic_op_std(int op, int __user *uaddr, int oparg, int *old) return ret; } -int futex_atomic_cmpxchg_std(int __user *uaddr, int oldval, int newval) +int futex_atomic_cmpxchg_std(int *uval, int __user *uaddr, + int oldval, int newval) { int ret; asm volatile( " sacf 256\n" "0: cs %1,%4,0(%5)\n" - "1: lr %0,%1\n" + "1: la %0,0\n" "2: sacf 0\n" EX_TABLE(0b,2b) EX_TABLE(1b,2b) : "=d" (ret), "+d" (oldval), "=m" (*uaddr) : "0" (-EFAULT), "d" (newval), "a" (uaddr), "m" (*uaddr) : "cc", "memory" ); + *uval = oldval; return ret; } |