diff options
| author | Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> | 2007-03-18 01:26:11 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-03-18 11:35:08 -0700 |
| commit | 303cd1535f6257b9fd8214534ca87b1a1567a2c5 (patch) | |
| tree | ec84da24cbfaae444c204df93c9391661012d854 | |
| parent | bad77057ed59892bd5c7807dcf0c2500e5ff1fe7 (diff) | |
| download | linux-303cd1535f6257b9fd8214534ca87b1a1567a2c5.tar.bz2 | |
[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 <rschultz@google.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Acked-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | arch/x86_64/kernel/process.c | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/arch/x86_64/kernel/process.c b/arch/x86_64/kernel/process.c index cbbc6adc1a92..d8d5ccc245c8 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; |