linux-kernel - [RFC][PATCH 1/3] exec: Move unshare_files down to avoid locks being dropped on exec.

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Date:   Sun, 16 Sep 2018 19:39:54 +0200
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Jeff Layton <jlayton@...nel.org>
Cc:     viro@...iv.linux.org.uk, berrange@...hat.com,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Oleg Nesterov <oleg@...hat.com>
Subject: [RFC][PATCH 1/3] exec: Move unshare_files down to avoid locks being dropped on exec.


Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 fs/exec.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 1ebf6e5a521d..6f6167ec08eb 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1252,6 +1252,7 @@ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
  */
 int flush_old_exec(struct linux_binprm * bprm)
 {
+	struct files_struct *displaced;
 	int retval;
 
 	/*
@@ -1291,6 +1292,12 @@ int flush_old_exec(struct linux_binprm * bprm)
 	flush_thread();
 	current->personality &= ~bprm->per_clear;
 
+	retval = unshare_files(&displaced);
+	if (retval)
+		goto out;
+	if (displaced)
+		put_files_struct(displaced);
+
 	/*
 	 * We have to apply CLOEXEC before we change whether the process is
 	 * dumpable (in setup_new_exec) to avoid a race with a process in userspace
@@ -1713,7 +1720,6 @@ static int __do_execve_file(int fd, struct filename *filename,
 {
 	char *pathbuf = NULL;
 	struct linux_binprm *bprm;
-	struct files_struct *displaced;
 	int retval;
 
 	if (IS_ERR(filename))
@@ -1735,14 +1741,10 @@ static int __do_execve_file(int fd, struct filename *filename,
 	 * further execve() calls fail. */
 	current->flags &= ~PF_NPROC_EXCEEDED;
 
-	retval = unshare_files(&displaced);
-	if (retval)
-		goto out_ret;
-
 	retval = -ENOMEM;
 	bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
 	if (!bprm)
-		goto out_files;
+		goto out_ret;
 
 	retval = prepare_bprm_creds(bprm);
 	if (retval)
@@ -1831,8 +1833,6 @@ static int __do_execve_file(int fd, struct filename *filename,
 	kfree(pathbuf);
 	if (filename)
 		putname(filename);
-	if (displaced)
-		put_files_struct(displaced);
 	return retval;
 
 out:
@@ -1849,9 +1849,6 @@ static int __do_execve_file(int fd, struct filename *filename,
 	free_bprm(bprm);
 	kfree(pathbuf);
 
-out_files:
-	if (displaced)
-		reset_files_struct(displaced);
 out_ret:
 	if (filename)
 		putname(filename);
-- 
2.17.1