From c0a79b229ac0e3a96fc00d5be65a498ceb06ef63 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Sat, 10 Mar 2007 00:19:49 -0800 Subject: [PATCH] [SPARC64]: Fix atomicity of TIF update in flush_thread() Fix atomicity of TIF update in flush_thread() for sparc64 Fixes correctly the race by using *_ti_thread_flag. Race : parent process executing : sys_ptrace() (lock_kernel()) (ptrace_get_task_struct(pid)) arch_ptrace() ptrace_detach() ptrace_disable(child); clear_singlestep(child); clear_tsk_thread_flag(child, TIF_SINGLESTEP); (which clears the TIF_SINGLESTEP flag atomically from a different process) (put_task_struct(child)) (unlock_kernel()) And at the same time, in the child process : sys_execve() do_execve() search_binary_handler() load_elf_binary() flush_old_exec() flush_thread() doing a non-atomic thread flag update Signed-off-by: Mathieu Desnoyers Signed-off-by: David S. Miller --- arch/sparc64/kernel/process.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/sparc64/kernel/process.c b/arch/sparc64/kernel/process.c index 7d75cd4eb297..b291060c25a6 100644 --- a/arch/sparc64/kernel/process.c +++ b/arch/sparc64/kernel/process.c @@ -413,8 +413,13 @@ void flush_thread(void) struct thread_info *t = current_thread_info(); struct mm_struct *mm; - if (t->flags & _TIF_ABI_PENDING) - t->flags ^= (_TIF_ABI_PENDING | _TIF_32BIT); + if (test_ti_thread_flag(t, TIF_ABI_PENDING)) { + clear_ti_thread_flag(t, TIF_ABI_PENDING); + if (test_ti_thread_flag(t, TIF_32BIT)) + clear_ti_thread_flag(t, TIF_32BIT); + else + set_ti_thread_flag(t, TIF_32BIT); + } mm = t->task->mm; if (mm)