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Subject[PATCH 5.4 196/388] proc: Use new infrastructure to fix deadlocks in execve
Date
From: Bernd Edlinger <bernd.edlinger@hotmail.de>

[ 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>
---
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 ebea9501afb84..4fdfe4faa74ee 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
--
2.25.1


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