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mqueue: lift mnt_want_write() outside ->i_mutex, clean up a bit

the way it abuses ->d_fsdata still needs to be killed, but that's
a separate story.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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commit 312b90fbed0e07f61d2f060789440a83df6bba23 1 parent 20fb193
Al Viro authored
Showing with 28 additions and 33 deletions.
  1. +28 −33 ipc/mqueue.c
61 ipc/mqueue.c
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@@ -726,7 +726,6 @@ static struct file *do_create(struct ipc_namespace *ipc_ns, struct inode *dir,
struct mq_attr *attr)
{
const struct cred *cred = current_cred();
- struct file *result;
int ret;
if (attr) {
@@ -748,21 +747,11 @@ static struct file *do_create(struct ipc_namespace *ipc_ns, struct inode *dir,
}
mode &= ~current_umask();
- ret = mnt_want_write(path->mnt);
- if (ret)
- return ERR_PTR(ret);
ret = vfs_create(dir, path->dentry, mode, true);
path->dentry->d_fsdata = NULL;
- if (!ret)
- result = dentry_open(path, oflag, cred);
- else
- result = ERR_PTR(ret);
- /*
- * dentry_open() took a persistent mnt_want_write(),
- * so we can now drop this one.
- */
- mnt_drop_write(path->mnt);
- return result;
+ if (ret)
+ return ERR_PTR(ret);
+ return dentry_open(path, oflag, cred);
}
/* Opens existing queue */
@@ -788,7 +777,9 @@ SYSCALL_DEFINE4(mq_open, const char __user *, u_name, int, oflag, umode_t, mode,
struct mq_attr attr;
int fd, error;
struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
- struct dentry *root = ipc_ns->mq_mnt->mnt_root;
+ struct vfsmount *mnt = ipc_ns->mq_mnt;
+ struct dentry *root = mnt->mnt_root;
+ int ro;
if (u_attr && copy_from_user(&attr, u_attr, sizeof(struct mq_attr)))
return -EFAULT;
@@ -802,6 +793,7 @@ SYSCALL_DEFINE4(mq_open, const char __user *, u_name, int, oflag, umode_t, mode,
if (fd < 0)
goto out_putname;
+ ro = mnt_want_write(mnt); /* we'll drop it in any case */
error = 0;
mutex_lock(&root->d_inode->i_mutex);
path.dentry = lookup_one_len(name, root, strlen(name));
@@ -809,7 +801,7 @@ SYSCALL_DEFINE4(mq_open, const char __user *, u_name, int, oflag, umode_t, mode,
error = PTR_ERR(path.dentry);
goto out_putfd;
}
- path.mnt = mntget(ipc_ns->mq_mnt);
+ path.mnt = mntget(mnt);
if (oflag & O_CREAT) {
if (path.dentry->d_inode) { /* entry already exists */
@@ -820,6 +812,10 @@ SYSCALL_DEFINE4(mq_open, const char __user *, u_name, int, oflag, umode_t, mode,
}
filp = do_open(&path, oflag);
} else {
+ if (ro) {
+ error = ro;
+ goto out;
+ }
filp = do_create(ipc_ns, root->d_inode,
&path, oflag, mode,
u_attr ? &attr : NULL);
@@ -845,6 +841,7 @@ SYSCALL_DEFINE4(mq_open, const char __user *, u_name, int, oflag, umode_t, mode,
fd = error;
}
mutex_unlock(&root->d_inode->i_mutex);
+ mnt_drop_write(mnt);
out_putname:
putname(name);
return fd;
@@ -857,40 +854,38 @@ SYSCALL_DEFINE1(mq_unlink, const char __user *, u_name)
struct dentry *dentry;
struct inode *inode = NULL;
struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
+ struct vfsmount *mnt = ipc_ns->mq_mnt;
name = getname(u_name);
if (IS_ERR(name))
return PTR_ERR(name);
- mutex_lock_nested(&ipc_ns->mq_mnt->mnt_root->d_inode->i_mutex,
- I_MUTEX_PARENT);
- dentry = lookup_one_len(name, ipc_ns->mq_mnt->mnt_root, strlen(name));
+ err = mnt_want_write(mnt);
+ if (err)
+ goto out_name;
+ mutex_lock_nested(&mnt->mnt_root->d_inode->i_mutex, I_MUTEX_PARENT);
+ dentry = lookup_one_len(name, mnt->mnt_root, strlen(name));
if (IS_ERR(dentry)) {
err = PTR_ERR(dentry);
goto out_unlock;
}
- if (!dentry->d_inode) {
- err = -ENOENT;
- goto out_err;
- }
-
inode = dentry->d_inode;
- if (inode)
+ if (!inode) {
+ err = -ENOENT;
+ } else {
ihold(inode);
- err = mnt_want_write(ipc_ns->mq_mnt);
- if (err)
- goto out_err;
- err = vfs_unlink(dentry->d_parent->d_inode, dentry);
- mnt_drop_write(ipc_ns->mq_mnt);
-out_err:
+ err = vfs_unlink(dentry->d_parent->d_inode, dentry);
+ }
dput(dentry);
out_unlock:
- mutex_unlock(&ipc_ns->mq_mnt->mnt_root->d_inode->i_mutex);
- putname(name);
+ mutex_unlock(&mnt->mnt_root->d_inode->i_mutex);
if (inode)
iput(inode);
+ mnt_drop_write(mnt);
+out_name:
+ putname(name);
return err;
}
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