From 4301db49e5569fbb729769bfaf9b21b858330543 Mon Sep 17 00:00:00 2001 From: Bernd Edlinger Date: Fri, 20 Mar 2020 21:27:24 +0100 Subject: [PATCH] proc: Use new infrastructure to fix deadlocks in execve [ 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 Signed-off-by: Eric W. Biederman Signed-off-by: Sasha Levin --- fs/proc/base.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index ebea9501afb8..4fdfe4faa74e 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -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