Messages in this thread | | | Date | Sat, 5 Nov 2011 13:31:46 +0400 | From | Vasiliy Kulikov <> | Subject | Re: Linus GIT - INFO: possible circular locking dependency detected |
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(cc'ed Andrew and Alexey)
On Thu, Nov 03, 2011 at 20:49 +0000, Luis Henriques wrote: > On Thu, Nov 03, 2011 at 11:57:20AM -0400, Miles Lane wrote: > ... > > I'm hitting the exact same problem, using a minimal .config file (can send > it if required), by just running "find /". > > I have bisected the problem and found that commit > aa6afca5bcaba8101f3ea09d5c3e4100b2b9f0e5 seems to be the cause of it.
procfs holds sig->cred_guard_mutex to ensure the target's credentials are not changed. It is held for a little timeslice. From the stack trace I don't understand how sys_execve() can happen with ->cred_guard_mutex held:
static struct dentry *proc_lookupfd_common(struct inode *dir, struct dentry *dentry, instantiate_t instantiate) { ... if (lock_trace(task)) goto out;
result = instantiate(dir, dentry, task, &fd); unlock_trace(task); ... }
static int lock_trace(struct task_struct *task) { int err = mutex_lock_killable(&task->signal->cred_guard_mutex); if (err) return err; if (!ptrace_may_access(task, PTRACE_MODE_ATTACH)) { mutex_unlock(&task->signal->cred_guard_mutex); return -EPERM; } return 0; }
proc_lookupfd_common() always exits without ->cred_guard_mutex held.
Thanks,
-- Vasiliy Kulikov http://www.openwall.com - bringing security into open computing environments
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