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proc: Use new infrastructure to fix deadlocks in execve

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[ Upstream commit 2db9dbf71bf98d02a0bf33e798e5bfd2a9944696 ]

This changes lock_trace to use the new exec_update_mutex
instead of cred_guard_mutex.

This fixes possible deadlocks when the trace is accessing
/proc/$pid/stack for instance.

This should be safe, as the credentials are only used for reading,
and task->mm is updated on execve under the new exec_update_mutex.

Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Bernd Edlinger 2020-03-20 21:27:24 +01:00 committed by Greg Kroah-Hartman
parent 0cd9783686
commit 4301db49e5
1 changed files with 3 additions and 3 deletions
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6
fs/proc/base.c
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@ -403,11 +403,11 @@ print0:
static int lock_trace(struct task_struct *task)
{
int err = mutex_lock_killable(&task->signal->cred_guard_mutex);
int err = mutex_lock_killable(&task->signal->exec_update_mutex);
if (err)
return err;
if (!ptrace_may_access(task, PTRACE_MODE_ATTACH_FSCREDS)) {
mutex_unlock(&task->signal->cred_guard_mutex);
mutex_unlock(&task->signal->exec_update_mutex);
return -EPERM;
}
return 0;
@ -415,7 +415,7 @@ static int lock_trace(struct task_struct *task)
static void unlock_trace(struct task_struct *task)
{
mutex_unlock(&task->signal->cred_guard_mutex);
mutex_unlock(&task->signal->exec_update_mutex);
}
#ifdef CONFIG_STACKTRACE