[PATCH] r/o bind mounts: elevate write count for ioctls()

Some ioctl()s can cause writes to the filesystem.  Take these, and make them
use mnt_want/drop_write() instead.

[AV: updated]

Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 68 insertions, 35 deletions

diff --git a/fs/ext3/ioctl.c b/fs/ext3/ioctl.c
index 023a070f55f1..0d0c70151642 100644
--- a/fs/ext3/ioctl.c
+++ b/fs/ext3/ioctl.c
@@ -12,6 +12,7 @@
 #include <linux/capability.h>
 #include <linux/ext3_fs.h>
 #include <linux/ext3_jbd.h>
+#include <linux/mount.h>
 #include <linux/time.h>
 #include <linux/compat.h>
 #include <linux/smp_lock.h>
@@ -38,14 +39,19 @@ int ext3_ioctl (struct inode * inode, struct file * filp, unsigned int cmd,
                 unsigned int oldflags;
                 unsigned int jflag;
 
-                if (IS_RDONLY(inode))
-                        return -EROFS;
+                err = mnt_want_write(filp->f_path.mnt);
+                if (err)
+                        return err;
 
-                if (!is_owner_or_cap(inode))
-                        return -EACCES;
+                if (!is_owner_or_cap(inode)) {
+                        err = -EACCES;
+                        goto flags_out;
+                }
 
-                if (get_user(flags, (int __user *) arg))
-                        return -EFAULT;
+                if (get_user(flags, (int __user *) arg)) {
+                        err = -EFAULT;
+                        goto flags_out;
+                }
 
                 if (!S_ISDIR(inode->i_mode))
                         flags &= ~EXT3_DIRSYNC_FL;
@@ -54,7 +60,8 @@ int ext3_ioctl (struct inode * inode, struct file * filp, unsigned int cmd,
                 /* Is it quota file? Do not allow user to mess with it */
                 if (IS_NOQUOTA(inode)) {
                         mutex_unlock(&inode->i_mutex);
-                        return -EPERM;
+                        err = -EPERM;
+                        goto flags_out;
                 }
                 oldflags = ei->i_flags;
 
@@ -70,7 +77,8 @@ int ext3_ioctl (struct inode * inode, struct file * filp, unsigned int cmd,
                 if ((flags ^ oldflags) & (EXT3_APPEND_FL | EXT3_IMMUTABLE_FL)) {
                         if (!capable(CAP_LINUX_IMMUTABLE)) {
                                 mutex_unlock(&inode->i_mutex);
-                                return -EPERM;
+                                err = -EPERM;
+                                goto flags_out;
                         }
                 }
 
@@ -81,7 +89,8 @@ int ext3_ioctl (struct inode * inode, struct file * filp, unsigned int cmd,
                 if ((jflag ^ oldflags) & (EXT3_JOURNAL_DATA_FL)) {
                         if (!capable(CAP_SYS_RESOURCE)) {
                                 mutex_unlock(&inode->i_mutex);
-                                return -EPERM;
+                                err = -EPERM;
+                                goto flags_out;
                         }
                 }
 
@@ -89,7 +98,8 @@ int ext3_ioctl (struct inode * inode, struct file * filp, unsigned int cmd,
                 handle = ext3_journal_start(inode, 1);
                 if (IS_ERR(handle)) {
                         mutex_unlock(&inode->i_mutex);
-                        return PTR_ERR(handle);
+                        err = PTR_ERR(handle);
+                        goto flags_out;
                 }
                 if (IS_SYNC(inode))
                         handle->h_sync = 1;
@@ -115,6 +125,8 @@ flags_err:
                 if ((jflag ^ oldflags) & (EXT3_JOURNAL_DATA_FL))
                         err = ext3_change_inode_journal_flag(inode, jflag);
                 mutex_unlock(&inode->i_mutex);
+flags_out:
+                mnt_drop_write(filp->f_path.mnt);
                 return err;
         }
         case EXT3_IOC_GETVERSION:
@@ -129,14 +141,18 @@ flags_err:
 
                 if (!is_owner_or_cap(inode))
                         return -EPERM;
-                if (IS_RDONLY(inode))
-                        return -EROFS;
-                if (get_user(generation, (int __user *) arg))
-                        return -EFAULT;
-
+                err = mnt_want_write(filp->f_path.mnt);
+                if (err)
+                        return err;
+                if (get_user(generation, (int __user *) arg)) {
+                        err = -EFAULT;
+                        goto setversion_out;
+                }
                 handle = ext3_journal_start(inode, 1);
-                if (IS_ERR(handle))
-                        return PTR_ERR(handle);
+                if (IS_ERR(handle)) {
+                        err = PTR_ERR(handle);
+                        goto setversion_out;
+                }
                 err = ext3_reserve_inode_write(handle, inode, &iloc);
                 if (err == 0) {
                         inode->i_ctime = CURRENT_TIME_SEC;
@@ -144,6 +160,8 @@ flags_err:
                         err = ext3_mark_iloc_dirty(handle, inode, &iloc);
                 }
                 ext3_journal_stop(handle);
+setversion_out:
+                mnt_drop_write(filp->f_path.mnt);
                 return err;
         }
 #ifdef CONFIG_JBD_DEBUG
@@ -179,18 +197,24 @@ flags_err:
                 }
                 return -ENOTTY;
         case EXT3_IOC_SETRSVSZ: {
+                int err;
 
                 if (!test_opt(inode->i_sb, RESERVATION) ||!S_ISREG(inode->i_mode))
                         return -ENOTTY;
 
-                if (IS_RDONLY(inode))
-                        return -EROFS;
+                err = mnt_want_write(filp->f_path.mnt);
+                if (err)
+                        return err;
 
-                if (!is_owner_or_cap(inode))
-                        return -EACCES;
+                if (!is_owner_or_cap(inode)) {
+                        err = -EACCES;
+                        goto setrsvsz_out;
+                }
 
-                if (get_user(rsv_window_size, (int __user *)arg))
-                        return -EFAULT;
+                if (get_user(rsv_window_size, (int __user *)arg)) {
+                        err = -EFAULT;
+                        goto setrsvsz_out;
+                }
 
                 if (rsv_window_size > EXT3_MAX_RESERVE_BLOCKS)
                         rsv_window_size = EXT3_MAX_RESERVE_BLOCKS;
@@ -208,7 +232,9 @@ flags_err:
                         rsv->rsv_goal_size = rsv_window_size;
                 }
                 mutex_unlock(&ei->truncate_mutex);
-                return 0;
+setrsvsz_out:
+                mnt_drop_write(filp->f_path.mnt);
+                return err;
         }
         case EXT3_IOC_GROUP_EXTEND: {
                 ext3_fsblk_t n_blocks_count;
@@ -218,17 +244,20 @@ flags_err:
                 if (!capable(CAP_SYS_RESOURCE))
                         return -EPERM;
 
-                if (IS_RDONLY(inode))
-                        return -EROFS;
-
-                if (get_user(n_blocks_count, (__u32 __user *)arg))
-                        return -EFAULT;
+                err = mnt_want_write(filp->f_path.mnt);
+                if (err)
+                        return err;
 
+                if (get_user(n_blocks_count, (__u32 __user *)arg)) {
+                        err = -EFAULT;
+                        goto group_extend_out;
+                }
                 err = ext3_group_extend(sb, EXT3_SB(sb)->s_es, n_blocks_count);
                 journal_lock_updates(EXT3_SB(sb)->s_journal);
                 journal_flush(EXT3_SB(sb)->s_journal);
                 journal_unlock_updates(EXT3_SB(sb)->s_journal);
-
+group_extend_out:
+                mnt_drop_write(filp->f_path.mnt);
                 return err;
         }
         case EXT3_IOC_GROUP_ADD: {
@@ -239,18 +268,22 @@ flags_err:
                 if (!capable(CAP_SYS_RESOURCE))
                         return -EPERM;
 
-                if (IS_RDONLY(inode))
-                        return -EROFS;
+                err = mnt_want_write(filp->f_path.mnt);
+                if (err)
+                        return err;
 
                 if (copy_from_user(&input, (struct ext3_new_group_input __user *)arg,
-                                sizeof(input)))
-                        return -EFAULT;
+                                sizeof(input))) {
+                        err = -EFAULT;
+                        goto group_add_out;
+                }
 
                 err = ext3_group_add(sb, &input);
                 journal_lock_updates(EXT3_SB(sb)->s_journal);
                 journal_flush(EXT3_SB(sb)->s_journal);
                 journal_unlock_updates(EXT3_SB(sb)->s_journal);
-
+group_add_out:
+                mnt_drop_write(filp->f_path.mnt);
                 return err;
         }