On 03/15, Al Viro wrote:
>
> On Fri, Mar 15, 2013 at 12:07:14AM -0400, Sasha Levin wrote:
> > Hi all,
> >
> > While fuzzing with trinity inside a KVM tools guest running latest -next
> > kernel
> > I've stumbled on the following.
> >
> > Dave Jones reported something similar, but that seemed to involve cgroup's
> > mutex
> > and didn't seem like it was the same issue as this one.
>
> Lovely... It's an execve() attempt on a "binary" that is, in fact, a procfs
> file (/proc/<pid>/stack),
probably... other lock_trace() callers can't generate this lockdep output
afaics.
> with its ->read() trying to grab ->cred_guard_mutex.
> The fact that it's seq_file-based is irrelevant here - all that matters is
> that we have ->read() for some file trying to grab ->cred_guard_mutex.
Yes, perhaps the patch below makes sense anyway as a cleanup, but obviously
it can't help.
Cough... I am shy to disclose my ignorance, but could you explain how
open_exec()->do_filp_open(MAY_EXEC) can succeed in this case? At least
acl_permission_check() looks as if open_exec() should fail...
Just curious, thanks in advance.
Oleg.
--- x/fs/proc/base.c
+++ x/fs/proc/base.c
@@ -317,12 +317,12 @@ static int proc_pid_stack(struct seq_fil
err = lock_trace(task);
if (!err) {
save_stack_trace_tsk(task, &trace);
+ unlock_trace(task);
for (i = 0; i < trace.nr_entries; i++) {
seq_printf(m, "[<%pK>] %pS\n",
(void *)entries[i], (void *)entries[i]);
}
- unlock_trace(task);
}
kfree(entries);
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