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SubjectRe: [PATCH 6/6] mqueue: fix mq_open() file descriptor leak on user-space processes
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On Thu, Feb 25, 2010 at 12:25 PM, Américo Wang <xiyou.wangcong@gmail.com> wrote:
> On Thu, Feb 25, 2010 at 12:00 PM, Xiaotian Feng <xtfeng@gmail.com> wrote:
>> 2010/2/25 Américo Wang <xiyou.wangcong@gmail.com>:
>>> On Tue, Feb 23, 2010 at 3:04 PM, André Goddard Rosa
>>> <andre.goddard@gmail.com> wrote:
>>>> It can be triggered by the following test program:
>>>>
>>>
>>> <snip>
>>>
>>>>
>>>> When not running valgrind, user-space program segfaults trying to execute
>>>> strerror(errno). With valgrind, it executes successfully and prints the
>>>> 5 open files: stdin, stdout, stderr, pipe[0] and pipe[1].
>>>>
>>>> Signed-off-by: André Goddard Rosa <andre.goddard@gmail.com>
>>>> ---
>>>
>>> The code has more than just this problem, could you please try
>>> my patch below?
>>>
>>> Thanks.
>>>
>>> ---------------------------->
>>>
>>> Clean up the failure path of sys_mq_open().
>>>
>>> Reorder the goto labels;
>>> Rename 'upsem' to 'upunlock';
>>> Remove some unused labels;
>>> Fix some wrong goto path.
>>>
>>
>> I think it's wrong to move dput after mntput
>
> Oh, this is to say mntget() should be called before lookup_one_len(),
> the original code seems wrong again...
>

How about the one below?
---------
Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index c79bd57..6824651 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -686,7 +686,7 @@ SYSCALL_DEFINE4(mq_open, const char __user *, u_name, int, oflag, mode_t, mode,
struct file *filp;
char *name;
struct mq_attr attr;
- int fd, error;
+ int fd, error = 0;
struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;

if (u_attr && copy_from_user(&attr, u_attr, sizeof(struct mq_attr)))
@@ -701,13 +701,13 @@ SYSCALL_DEFINE4(mq_open, const char __user *, u_name, int, oflag, mode_t, mode,
if (fd < 0)
goto out_putname;

+ mntget(ipc_ns->mq_mnt);
mutex_lock(&ipc_ns->mq_mnt->mnt_root->d_inode->i_mutex);
dentry = lookup_one_len(name, ipc_ns->mq_mnt->mnt_root, strlen(name));
if (IS_ERR(dentry)) {
error = PTR_ERR(dentry);
- goto out_err;
+ goto out_unlock;
}
- mntget(ipc_ns->mq_mnt);

if (oflag & O_CREAT) {
if (dentry->d_inode) { /* entry already exists */
@@ -731,24 +731,23 @@ SYSCALL_DEFINE4(mq_open, const char __user *, u_name, int, oflag, mode_t, mode,

if (IS_ERR(filp)) {
error = PTR_ERR(filp);
- goto out_putfd;
+ goto out;
}

fd_install(fd, filp);
- goto out_upsem;
+ goto out_unlock;

out:
dput(dentry);
- mntput(ipc_ns->mq_mnt);
-out_putfd:
- put_unused_fd(fd);
-out_err:
- fd = error;
-out_upsem:
+out_unlock:
mutex_unlock(&ipc_ns->mq_mnt->mnt_root->d_inode->i_mutex);
+ if (error) {
+ mntput(ipc_ns->mq_mnt);
+ put_unused_fd(fd);
+ }
out_putname:
putname(name);
- return fd;
+ return error;
}

SYSCALL_DEFINE1(mq_unlink, const char __user *, u_name)
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