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>

1 files changed, 43 insertions, 17 deletions

diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index d6b2b83de36..8e5cad020c3 100644
--- 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;
 }