From 6b335d9c80d7f3c2a3f6545f664ae9007a0f3821 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Tue, 22 Apr 2008 04:45:46 -0400
Subject: [PATCH] [PATCH] close race in unshare_files()
updating current->files requires task_lock
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
kernel/fork.c | 20 +++++++++-----------
1 file changed, 9 insertions(+), 11 deletions(-)
diff --git a/kernel/fork.c b/kernel/fork.c
index 89fe414645e9..76f05a08062b 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -805,12 +805,6 @@ static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
goto out;
}
- /*
- * Note: we may be using current for both targets (See exec.c)
- * This works because we cache current->files (old) as oldf. Don't
- * break this.
- */
- tsk->files = NULL;
newf = dup_fd(oldf, &error);
if (!newf)
goto out;
@@ -855,7 +849,8 @@ static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
int unshare_files(void)
{
struct files_struct *files = current->files;
- int rc;
+ struct files_struct *newf;
+ int error = 0;
BUG_ON(!files);
@@ -866,10 +861,13 @@ int unshare_files(void)
atomic_inc(&files->count);
return 0;
}
- rc = copy_files(0, current);
- if(rc)
- current->files = files;
- return rc;
+ newf = dup_fd(files, &error);
+ if (newf) {
+ task_lock(current);
+ current->files = newf;
+ task_unlock(current);
+ }
+ return error;
}
EXPORT_SYMBOL(unshare_files);