ARM: 8226/1: cacheflush: get rid of restarting block

We cannot restart cacheflush safely if a process provides user-defined
signal handler and signal is pending. In this case -EINTR is returned
and it is expected that process re-invokes syscall. However, there are
a few problems with that:
 * looks like nobody bothers checking return value from cacheflush
 * but if it did, we don't provide the restart address for that, so the
   process has to use the same range again
 * ...and again, what might lead to looping forever

So, remove cacheflush restarting code and terminate cache flushing
as early as fatal signal is pending.

Cc: stable@vger.kernel.org # 3.12+
Reported-by: Chanho Min <chanho.min@lge.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 2 insertions, 40 deletions

diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index fc44d3761f9e..ce73ab635414 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -44,16 +44,6 @@ struct cpu_context_save {
         __u32   extra[2];               /* Xscale 'acc' register, etc */
 };
 
-struct arm_restart_block {
-        union {
-                /* For user cache flushing */
-                struct {
-                        unsigned long start;
-                        unsigned long end;
-                } cache;
-        };
-};
-
 /*
  * low level task data that entry.S needs immediate access to.
  * __switch_to() assumes cpu_context follows immediately after cpu_domain.
@@ -79,7 +69,6 @@ struct thread_info {
         unsigned long           thumbee_state;  /* ThumbEE Handler Base register */
 #endif
         struct restart_block    restart_block;
-        struct arm_restart_block        arm_restart_block;
 };
 
 #define INIT_THREAD_INFO(tsk)                                           \
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 0c8b10801d36..9f5d81881eb6 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -533,8 +533,6 @@ static int bad_syscall(int n, struct pt_regs *regs)
         return regs->ARM_r0;
 }
 
-static long do_cache_op_restart(struct restart_block *);
-
 static inline int
 __do_cache_op(unsigned long start, unsigned long end)
 {
@@ -543,24 +541,8 @@ __do_cache_op(unsigned long start, unsigned long end)
         do {
                 unsigned long chunk = min(PAGE_SIZE, end - start);
 
-                if (signal_pending(current)) {
-                        struct thread_info *ti = current_thread_info();
-
-                        ti->restart_block = (struct restart_block) {
-                                .fn     = do_cache_op_restart,
-                        };
-
-                        ti->arm_restart_block = (struct arm_restart_block) {
-                                {
-                                        .cache = {
-                                                .start  = start,
-                                                .end    = end,
-                                        },
-                                },
-                        };
-
-                        return -ERESTART_RESTARTBLOCK;
-                }
+                if (fatal_signal_pending(current))
+                        return 0;
 
                 ret = flush_cache_user_range(start, start + chunk);
                 if (ret)
@@ -573,15 +555,6 @@ __do_cache_op(unsigned long start, unsigned long end)
         return 0;
 }
 
-static long do_cache_op_restart(struct restart_block *unused)
-{
-        struct arm_restart_block *restart_block;
-
-        restart_block = &current_thread_info()->arm_restart_block;
-        return __do_cache_op(restart_block->cache.start,
-                             restart_block->cache.end);
-}
-
 static inline int
 do_cache_op(unsigned long start, unsigned long end, int flags)
 {