From 303cd1535f6257b9fd8214534ca87b1a1567a2c5 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Sun, 18 Mar 2007 01:26:11 -0800 Subject: [PATCH] [PATCH] Fix atomicity of TIF update in flush_thread() for x86_64 Fix atomicity of TIF update in flush_thread() for x86_64 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: Rebecca Schultz Signed-off-by: Mathieu Desnoyers Acked-by: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/x86_64/kernel/process.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/arch/x86_64/kernel/process.c b/arch/x86_64/kernel/process.c index cbbc6adc1a..d8d5ccc245 100644 --- a/arch/x86_64/kernel/process.c +++ b/arch/x86_64/kernel/process.c @@ -382,14 +382,17 @@ void exit_thread(void) void flush_thread(void) { struct task_struct *tsk = current; - struct thread_info *t = current_thread_info(); - if (t->flags & _TIF_ABI_PENDING) { - t->flags ^= (_TIF_ABI_PENDING | _TIF_IA32); - if (t->flags & _TIF_IA32) + if (test_tsk_thread_flag(tsk, TIF_ABI_PENDING)) { + clear_tsk_thread_flag(tsk, TIF_ABI_PENDING); + if (test_tsk_thread_flag(tsk, TIF_IA32)) { + clear_tsk_thread_flag(tsk, TIF_IA32); + } else { + set_tsk_thread_flag(tsk, TIF_IA32); current_thread_info()->status |= TS_COMPAT; + } } - t->flags &= ~_TIF_DEBUG; + clear_tsk_thread_flag(tsk, TIF_DEBUG); tsk->thread.debugreg0 = 0; tsk->thread.debugreg1 = 0; -- 2.20.1