[PATCH] Fix double decrement of mqueue_mnt->mnt_count in sys_mq_open
Fixed the refcounting on failure exits in sys_mq_open() and
cleaned the logics up. Rules are actually pretty simple - dentry_open()
expects vfsmount and dentry to be pinned down and it either transfers
them into created struct file or drops them. Old code had been very
confused in that area - if dentry_open() had failed either in do_open()
or do_create(), we ended up dentry and mqueue_mnt dropped twice, once
by dentry_open() cleanup and then by sys_mq_open().
Fix consists of making the rules for do_create() and do_open()
same as for dentry_open() and updating the sys_mq_open() accordingly;
that actually leads to more straightforward code and less work on
normal path.
Signed-off-by: Al Viro <aviro@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 4e776f9..59302fc 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -599,15 +599,16 @@
static struct file *do_create(struct dentry *dir, struct dentry *dentry,
int oflag, mode_t mode, struct mq_attr __user *u_attr)
{
- struct file *filp;
struct mq_attr attr;
int ret;
- if (u_attr != NULL) {
+ if (u_attr) {
+ ret = -EFAULT;
if (copy_from_user(&attr, u_attr, sizeof(attr)))
- return ERR_PTR(-EFAULT);
+ goto out;
+ ret = -EINVAL;
if (!mq_attr_ok(&attr))
- return ERR_PTR(-EINVAL);
+ goto out;
/* store for use during create */
dentry->d_fsdata = &attr;
}
@@ -616,13 +617,14 @@
ret = vfs_create(dir->d_inode, dentry, mode, NULL);
dentry->d_fsdata = NULL;
if (ret)
- return ERR_PTR(ret);
+ goto out;
- filp = dentry_open(dentry, mqueue_mnt, oflag);
- if (!IS_ERR(filp))
- dget(dentry);
+ return dentry_open(dentry, mqueue_mnt, oflag);
- return filp;
+out:
+ dput(dentry);
+ mntput(mqueue_mnt);
+ return ERR_PTR(ret);
}
/* Opens existing queue */
@@ -630,20 +632,20 @@
{
static int oflag2acc[O_ACCMODE] = { MAY_READ, MAY_WRITE,
MAY_READ | MAY_WRITE };
- struct file *filp;
- if ((oflag & O_ACCMODE) == (O_RDWR | O_WRONLY))
+ if ((oflag & O_ACCMODE) == (O_RDWR | O_WRONLY)) {
+ dput(dentry);
+ mntput(mqueue_mnt);
return ERR_PTR(-EINVAL);
+ }
- if (permission(dentry->d_inode, oflag2acc[oflag & O_ACCMODE], NULL))
+ if (permission(dentry->d_inode, oflag2acc[oflag & O_ACCMODE], NULL)) {
+ dput(dentry);
+ mntput(mqueue_mnt);
return ERR_PTR(-EACCES);
+ }
- filp = dentry_open(dentry, mqueue_mnt, oflag);
-
- if (!IS_ERR(filp))
- dget(dentry);
-
- return filp;
+ return dentry_open(dentry, mqueue_mnt, oflag);
}
asmlinkage long sys_mq_open(const char __user *u_name, int oflag, mode_t mode,
@@ -671,17 +673,20 @@
if (oflag & O_CREAT) {
if (dentry->d_inode) { /* entry already exists */
- filp = (oflag & O_EXCL) ? ERR_PTR(-EEXIST) :
- do_open(dentry, oflag);
+ error = -EEXIST;
+ if (oflag & O_EXCL)
+ goto out;
+ filp = do_open(dentry, oflag);
} else {
filp = do_create(mqueue_mnt->mnt_root, dentry,
oflag, mode, u_attr);
}
- } else
- filp = (dentry->d_inode) ? do_open(dentry, oflag) :
- ERR_PTR(-ENOENT);
-
- dput(dentry);
+ } else {
+ error = -ENOENT;
+ if (!dentry->d_inode)
+ goto out;
+ filp = do_open(dentry, oflag);
+ }
if (IS_ERR(filp)) {
error = PTR_ERR(filp);
@@ -692,8 +697,10 @@
fd_install(fd, filp);
goto out_upsem;
-out_putfd:
+out:
+ dput(dentry);
mntput(mqueue_mnt);
+out_putfd:
put_unused_fd(fd);
out_err:
fd = error;