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From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: matthew.garrett@nebula.com, yuchao0@huawei.com, tytso@mit.edu,
	darrick.wong@oracle.com, ard.biesheuvel@linaro.org,
	josef@toxicpanda.com, clm@fb.com, adilger.kernel@dilger.ca,
	viro@zeniv.linux.org.uk, jack@suse.com, dsterba@suse.com,
	jaegeuk@kernel.org, jk@ozlabs.org
Cc: reiserfs-devel@vger.kernel.org, linux-efi@vger.kernel.org,
	devel@lists.orangefs.org, linux-kernel@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net,
	linux-xfs@vger.kernel.org, linux-mm@kvack.org,
	linux-nilfs@vger.kernel.org, linux-mtd@lists.infradead.org,
	ocfs2-devel@oss.oracle.com, linux-fsdevel@vger.kernel.org,
	linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org
Subject: [PATCH 4/7] vfs: don't allow most setxattr to immutable files
Date: Fri, 21 Jun 2019 16:57:23 -0700
Message-ID: <156116144305.1664939.3544724373475771930.stgit@magnolia> (raw)
In-Reply-To: <156116141046.1664939.11424021489724835645.stgit@magnolia>

From: Darrick J. Wong <darrick.wong@oracle.com>

The chattr manpage has this to say about immutable files:

"A file with the 'i' attribute cannot be modified: it cannot be deleted
or renamed, no link can be created to this file, most of the file's
metadata can not be modified, and the file can not be opened in write
mode."

However, we don't actually check the immutable flag in the setattr code,
which means that we can update inode flags and project ids and extent
size hints on supposedly immutable files.  Therefore, reject setflags
and fssetxattr calls on an immutable file if the file is immutable and
will remain that way.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/inode.c |   27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)


diff --git a/fs/inode.c b/fs/inode.c
index 6374ad2ef25b..220caefc31f7 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2204,6 +2204,14 @@ int vfs_ioc_setflags_check(struct inode *inode, int oldflags, int flags)
 	    !capable(CAP_LINUX_IMMUTABLE))
 		return -EPERM;
 
+	/*
+	 * We aren't allowed to change any other flags if the immutable flag is
+	 * already set and is not being unset.
+	 */
+	if ((oldflags & FS_IMMUTABLE_FL) && (flags & FS_IMMUTABLE_FL) &&
+	    oldflags != flags)
+		return -EPERM;
+
 	return 0;
 }
 EXPORT_SYMBOL(vfs_ioc_setflags_check);
@@ -2246,6 +2254,25 @@ int vfs_ioc_fssetxattr_check(struct inode *inode, const struct fsxattr *old_fa,
 	    !S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
 		return -EINVAL;
 
+	/*
+	 * We aren't allowed to change any fields if the immutable flag is
+	 * already set and is not being unset.
+	 */
+	if ((old_fa->fsx_xflags & FS_XFLAG_IMMUTABLE) &&
+	    (fa->fsx_xflags & FS_XFLAG_IMMUTABLE)) {
+		if (old_fa->fsx_xflags != fa->fsx_xflags)
+			return -EPERM;
+		if (old_fa->fsx_projid != fa->fsx_projid)
+			return -EPERM;
+		if ((fa->fsx_xflags & (FS_XFLAG_EXTSIZE |
+				       FS_XFLAG_EXTSZINHERIT)) &&
+		    old_fa->fsx_extsize != fa->fsx_extsize)
+			return -EPERM;
+		if ((old_fa->fsx_xflags & FS_XFLAG_COWEXTSIZE) &&
+		    old_fa->fsx_cowextsize != fa->fsx_cowextsize)
+			return -EPERM;
+	}
+
 	/* Extent size hints of zero turn off the flags. */
 	if (fa->fsx_extsize == 0)
 		fa->fsx_xflags &= ~(FS_XFLAG_EXTSIZE | FS_XFLAG_EXTSZINHERIT);


  parent reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-21 23:56 [PATCH v4 0/7] vfs: make immutable files actually immutable Darrick J. Wong
2019-06-21 23:56 ` [PATCH 1/7] mm/fs: don't allow writes to immutable files Darrick J. Wong
2019-06-24 11:13   ` Jan Kara
2019-06-21 23:57 ` [PATCH 2/7] vfs: flush and wait for io when setting the immutable flag via SETFLAGS Darrick J. Wong
2019-06-24 11:37   ` Jan Kara
2019-06-24 21:58     ` Darrick J. Wong
2019-06-25  3:04       ` [Ocfs2-devel] " Darrick J. Wong
2019-06-25  7:08         ` Jan Kara
2019-06-24 15:33   ` Jan Kara
2019-06-24 16:36     ` Darrick J. Wong
2019-06-21 23:57 ` [PATCH 3/7] vfs: flush and wait for io when setting the immutable flag via FSSETXATTR Darrick J. Wong
2019-06-21 23:57 ` Darrick J. Wong [this message]
2019-06-21 23:57 ` [PATCH 5/7] xfs: refactor setflags to use setattr code directly Darrick J. Wong
2019-06-21 23:57 ` [PATCH 6/7] xfs: clean up xfs_merge_ioc_xflags Darrick J. Wong
2019-06-21 23:57 ` [PATCH 7/7] vfs: don't allow writes to swap files Darrick J. Wong
2019-06-25 10:36 ` [PATCH v4 0/7] vfs: make immutable files actually immutable Christoph Hellwig
2019-06-25 18:03   ` Darrick J. Wong
2019-06-25 20:37     ` Andreas Dilger

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