[PATCH AUTOSEL 5.4 202/330] proc: Use new infrastructure to fix deadlocks in execve
From: Sasha Levin <sashal@kernel.org>
Date: 2020-09-18 03:02:53
Also in:
lkml
Subsystem:
filesystems (vfs and infrastructure), proc filesystem, the rest · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds
From: Bernd Edlinger <redacted> [ 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 <redacted> Signed-off-by: Eric W. Biederman <redacted> 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
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2.25.1