3.2-stable review patch. If anyone has any objections, please let me know.
------------------ From: "Luck, Tony" <[email protected]> commit c76f39bddb84f93f70a5520d9253ec0317bec216 upstream. Michel Lespinasse cleaned up the futex calling conventions in commit 37a9d912b24f ("futex: Sanitize cmpxchg_futex_value_locked API"). But the ia64 implementation was subtly broken. Gcc does not know that register "r8" will be updated by the fault handler if the cmpxchg instruction takes an exception. So it feels safe in letting the initialization of r8 slide to after the cmpxchg. Result: we always return 0 whether the user address faulted or not. Fix by moving the initialization of r8 into the __asm__ code so gcc won't move it. Reported-by: <[email protected]> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=42757 Tested-by: <[email protected]> Acked-by: Michel Lespinasse <[email protected]> Signed-off-by: Tony Luck <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/ia64/include/asm/futex.h | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) --- a/arch/ia64/include/asm/futex.h +++ b/arch/ia64/include/asm/futex.h @@ -107,15 +107,16 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, return -EFAULT; { - register unsigned long r8 __asm ("r8") = 0; + register unsigned long r8 __asm ("r8"); unsigned long prev; __asm__ __volatile__( " mf;; \n" - " mov ar.ccv=%3;; \n" - "[1:] cmpxchg4.acq %0=[%1],%2,ar.ccv \n" + " mov %0=r0 \n" + " mov ar.ccv=%4;; \n" + "[1:] cmpxchg4.acq %1=[%2],%3,ar.ccv \n" " .xdata4 \"__ex_table\", 1b-., 2f-. \n" "[2:]" - : "=r" (prev) + : "=r" (r8), "=r" (prev) : "r" (uaddr), "r" (newval), "rO" ((long) (unsigned) oldval) : "memory"); -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
