From f144e7c7272bf527c380bffaa5e789dc28a09d8d Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Sat, 10 Mar 2007 03:23:03 -0500 Subject: [PATCH] [POWERPC] Fix atomicity of TIF update in flush_thread() Fix atomicity of TIF update in flush_thread() for powerpc Fixes it correctly with *_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 Applies on 2.6.20. Signed-off-by: Mathieu Desnoyers Signed-off-by: Paul Mackerras --- arch/powerpc/kernel/process.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index f3d4dd580dd..e53b2988d1b 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -465,8 +465,13 @@ void flush_thread(void) #ifdef CONFIG_PPC64 struct thread_info *t = current_thread_info(); - 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); + } #endif discard_lazy_cpu_state(); -- 2.41.0