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ext4: don't allow any modifications to an immutable file

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Don't allow any modifications to a file that's marked immutable, which
means that we have to flush all the writable pages to make the readonly
and we have to check the setattr/setflags parameters more closely.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
This commit is contained in:
Darrick J. Wong 2019-06-09 21:41:41 -04:00 committed by Theodore Ts'o
parent a49773064b
commit 2e53840362
1 changed files with 45 additions and 1 deletions
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46
fs/ext4/ioctl.c
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@ -269,6 +269,29 @@ static int uuid_is_zero(__u8 u[16])
}
#endif
/*
* If immutable is set and we are not clearing it, we're not allowed to change
* anything else in the inode. Don't error out if we're only trying to set
* immutable on an immutable file.
*/
static int ext4_ioctl_check_immutable(struct inode *inode, __u32 new_projid,
unsigned int flags)
{
struct ext4_inode_info *ei = EXT4_I(inode);
unsigned int oldflags = ei->i_flags;
if (!(oldflags & EXT4_IMMUTABLE_FL) || !(flags & EXT4_IMMUTABLE_FL))
return 0;
if ((oldflags & ~EXT4_IMMUTABLE_FL) != (flags & ~EXT4_IMMUTABLE_FL))
return -EPERM;
if (ext4_has_feature_project(inode->i_sb) &&
__kprojid_val(ei->i_projid) != new_projid)
return -EPERM;
return 0;
}
static int ext4_ioctl_setflags(struct inode *inode,
unsigned int flags)
{
@ -340,6 +363,20 @@ static int ext4_ioctl_setflags(struct inode *inode,
}
}
/*
* Wait for all pending directio and then flush all the dirty pages
* for this file. The flush marks all the pages readonly, so any
* subsequent attempt to write to the file (particularly mmap pages)
* will come through the filesystem and fail.
*/
if (S_ISREG(inode->i_mode) && !IS_IMMUTABLE(inode) &&
(flags & EXT4_IMMUTABLE_FL)) {
inode_dio_wait(inode);
err = filemap_write_and_wait(inode->i_mapping);
if (err)
goto flags_out;
}
handle = ext4_journal_start(inode, EXT4_HT_INODE, 1);
if (IS_ERR(handle)) {
err = PTR_ERR(handle);
@ -769,7 +806,11 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
return err;
inode_lock(inode);
err = ext4_ioctl_setflags(inode, flags);
err = ext4_ioctl_check_immutable(inode,
from_kprojid(&init_user_ns, ei->i_projid),
flags);
if (!err)
err = ext4_ioctl_setflags(inode, flags);
inode_unlock(inode);
mnt_drop_write_file(filp);
return err;
@ -1139,6 +1180,9 @@ resizefs_out:
goto out;
flags = (ei->i_flags & ~EXT4_FL_XFLAG_VISIBLE) |
(flags & EXT4_FL_XFLAG_VISIBLE);
err = ext4_ioctl_check_immutable(inode, fa.fsx_projid, flags);
if (err)
goto out;
err = ext4_ioctl_setflags(inode, flags);
if (err)
goto out;