Messages in this thread Patch in this message | | | Date | Fri, 15 Mar 2013 19:19:56 +0100 | From | Oleg Nesterov <> | Subject | Re: vfs: lockdep splat with prepare_bprm_creds |
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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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