nilfs2: use mnt_want_write in ioctls where write access is needed

A few nilfs2 ioctls need to ask for and then later release write
access to the mount in order to avoid potential write to read-only
mounts.

This adds the missing mnt_want_write and mnt_drop_write in
nilfs_ioctl_change_cpmode, nilfs_ioctl_delete_checkpoint, and
nilfs_ioctl_clean_segments.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index d6b2b83..8e5cad0 100644 (file)
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -26,6 +26,7 @@
 #include <linux/capability.h>  /* capable() */
 #include <linux/uaccess.h>     /* copy_from_user(), copy_to_user() */
 #include <linux/vmalloc.h>
+#include <linux/mount.h>       /* mnt_want_write(), mnt_drop_write() */
 #include <linux/nilfs2_fs.h>
 #include "nilfs.h"
 #include "segment.h"
@@ -107,20 +108,28 @@ static int nilfs_ioctl_change_cpmode(struct inode *inode, struct file *filp,
 
        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;
+
+       ret = mnt_want_write(filp->f_path.mnt);
+       if (ret)
+               return ret;
+
+       ret = -EFAULT;
        if (copy_from_user(&cpmode, argp, sizeof(cpmode)))
-               return -EFAULT;
+               goto out;
 
        mutex_lock(&nilfs->ns_mount_mutex);
+
        nilfs_transaction_begin(inode->i_sb, &ti, 0);
        ret = nilfs_cpfile_change_cpmode(
                cpfile, cpmode.cm_cno, cpmode.cm_mode);
-       if (unlikely(ret < 0)) {
+       if (unlikely(ret < 0))
                nilfs_transaction_abort(inode->i_sb);
-               mutex_unlock(&nilfs->ns_mount_mutex);
-               return ret;
-       }
-       nilfs_transaction_commit(inode->i_sb); /* never fails */
+       else
+               nilfs_transaction_commit(inode->i_sb); /* never fails */
+
        mutex_unlock(&nilfs->ns_mount_mutex);
+out:
+       mnt_drop_write(filp->f_path.mnt);
        return ret;
 }
 
@@ -135,16 +144,23 @@ nilfs_ioctl_delete_checkpoint(struct inode *inode, struct file *filp,
 
        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;
+
+       ret = mnt_want_write(filp->f_path.mnt);
+       if (ret)
+               return ret;
+
+       ret = -EFAULT;
        if (copy_from_user(&cno, argp, sizeof(cno)))
-               return -EFAULT;
+               goto out;
 
        nilfs_transaction_begin(inode->i_sb, &ti, 0);
        ret = nilfs_cpfile_delete_checkpoint(cpfile, cno);
-       if (unlikely(ret < 0)) {
+       if (unlikely(ret < 0))
                nilfs_transaction_abort(inode->i_sb);
-               return ret;
-       }
-       nilfs_transaction_commit(inode->i_sb); /* never fails */
+       else
+               nilfs_transaction_commit(inode->i_sb); /* never fails */
+out:
+       mnt_drop_write(filp->f_path.mnt);
        return ret;
 }
 
@@ -496,12 +512,19 @@ static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp,
        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;
 
+       ret = mnt_want_write(filp->f_path.mnt);
+       if (ret)
+               return ret;
+
+       ret = -EFAULT;
        if (copy_from_user(argv, argp, sizeof(argv)))
-               return -EFAULT;
+               goto out;
 
+       ret = -EINVAL;
        nsegs = argv[4].v_nmembs;
        if (argv[4].v_size != argsz[4])
-               return -EINVAL;
+               goto out;
+
        /*
         * argv[4] points to segment numbers this ioctl cleans.  We
         * use kmalloc() for its buffer because memory used for the
@@ -509,9 +532,10 @@ static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp,
         */
        kbufs[4] = memdup_user((void __user *)(unsigned long)argv[4].v_base,
                               nsegs * sizeof(__u64));
-       if (IS_ERR(kbufs[4]))
-               return PTR_ERR(kbufs[4]);
-
+       if (IS_ERR(kbufs[4])) {
+               ret = PTR_ERR(kbufs[4]);
+               goto out;
+       }
        nilfs = NILFS_SB(inode->i_sb)->s_nilfs;
 
        for (n = 0; n < 4; n++) {
@@ -563,10 +587,12 @@ static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp,
                nilfs_remove_all_gcinode(nilfs);
        clear_nilfs_gc_running(nilfs);
 
- out_free:
+out_free:
        while (--n >= 0)
                vfree(kbufs[n]);
        kfree(kbufs[4]);
+out:
+       mnt_drop_write(filp->f_path.mnt);
        return ret;
 }