Messages in this thread | | | From | "Eric W. Biederman" <> | Date | Wed, 06 Jul 2022 16:15:17 -0500 | Subject | Re: [PATCH] ptrace: fix clearing of JOBCTL_TRACED in ptrace_unfreeze_traced() |
| |
Sven Schnelle <svens@linux.ibm.com> writes:
> CI reported the following splat while running the strace testsuite: > > [ 3976.640309] WARNING: CPU: 1 PID: 3570031 at kernel/ptrace.c:272 ptrace_check_attach+0x12e/0x178 > [ 3976.640391] CPU: 1 PID: 3570031 Comm: strace Tainted: G OE 5.19.0-20220624.rc3.git0.ee819a77d4e7.300.fc36.s390x #1 > [ 3976.640410] Hardware name: IBM 3906 M04 704 (z/VM 7.1.0) > [ 3976.640452] Call Trace: > [ 3976.640454] [<00000000ab4b645a>] ptrace_check_attach+0x132/0x178 > [ 3976.640457] ([<00000000ab4b6450>] ptrace_check_attach+0x128/0x178) > [ 3976.640460] [<00000000ab4b6cde>] __s390x_sys_ptrace+0x86/0x160 > [ 3976.640463] [<00000000ac03fcec>] __do_syscall+0x1d4/0x200 > [ 3976.640468] [<00000000ac04e312>] system_call+0x82/0xb0 > [ 3976.640470] Last Breaking-Event-Address: > [ 3976.640471] [<00000000ab4ea3c8>] wait_task_inactive+0x98/0x190 > > This is because JOBCTL_TRACED is set, but the task is not in TASK_TRACED > state. Caused by ptrace_unfreeze_traced() which does: > > task->jobctl &= ~TASK_TRACED > > but it should be: > > task->jobctl &= ~JOBCTL_TRACED
That would definitely do it. I had to think about it for a few minutes to see how it explains some of the stranger behavior but it explains all of the funny behavior I have seen.
Thank you for tracking this down.
The fact the original bug report was on s390 had me somehow thinking this was s390 only.
I will double check everything get this in linux-next and then send this to Linus.
Eric
> Fixes: 31cae1eaae4f ("sched,signal,ptrace: Rework TASK_TRACED, TASK_STOPPED state") > Signed-off-by: Sven Schnelle <svens@linux.ibm.com> > --- > kernel/ptrace.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/ptrace.c b/kernel/ptrace.c > index 156a99283b11..1893d909e45c 100644 > --- a/kernel/ptrace.c > +++ b/kernel/ptrace.c > @@ -222,7 +222,7 @@ static void ptrace_unfreeze_traced(struct task_struct *task) > if (lock_task_sighand(task, &flags)) { > task->jobctl &= ~JOBCTL_PTRACE_FROZEN; > if (__fatal_signal_pending(task)) { > - task->jobctl &= ~TASK_TRACED; > + task->jobctl &= ~JOBCTL_TRACED; > wake_up_state(task, __TASK_TRACED); > } > unlock_task_sighand(task, &flags);
| |