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authorMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>2007-03-18 01:26:11 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-03-18 11:35:08 -0700
commit303cd1535f6257b9fd8214534ca87b1a1567a2c5 (patch)
treeec84da24cbfaae444c204df93c9391661012d854
parentbad77057ed59892bd5c7807dcf0c2500e5ff1fe7 (diff)
[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.c13
1 files changed, 8 insertions, 5 deletions
diff --git a/arch/x86_64/kernel/process.c b/arch/x86_64/kernel/process.c
index cbbc6adc1a9..d8d5ccc245c 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;