[04/15] xfs: update ctime and remove suid before cloning files
diff mbox series

Message ID 153870030069.29072.11055871953561649172.stgit@magnolia
State New
Headers show
Series
  • fs: fixes for serious clone/dedupe problems
Related show

Commit Message

Darrick J. Wong Oct. 5, 2018, 12:45 a.m. UTC
From: Darrick J. Wong <darrick.wong@oracle.com>

Before cloning into a file, update the ctime and remove sensitive
attributes like suid, just like we'd do for a regular file write.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/xfs_reflink.c |   25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

Comments

Dave Chinner Oct. 5, 2018, 5:30 a.m. UTC | #1
On Thu, Oct 04, 2018 at 05:45:00PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Before cloning into a file, update the ctime and remove sensitive
> attributes like suid, just like we'd do for a regular file write.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  fs/xfs/xfs_reflink.c |   25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)

Looks good.

Reviewed-by: Dave Chinner <dchinner@redhat.com>

Because this fixes a security related problem, I'm going to push
this with the data corruption fixes.

Cheers,

Dave.
Christoph Hellwig Oct. 6, 2018, 10:35 a.m. UTC | #2
>  STATIC int
>  xfs_reflink_remap_prep(
> @@ -1302,6 +1303,30 @@ xfs_reflink_remap_prep(
>  	/* Zap any page cache for the destination file's range. */
>  	truncate_inode_pages_range(&inode_out->i_data, pos_out,
>  				   PAGE_ALIGN(pos_out + len) - 1);
> +
> +	/* If we're altering the file contents... */
> +	if (!is_dedupe) {

Nipick - even a clone might not alter the file content, we just have
no guarantee.  So maybe change the comment to:

	/* If we may alter the file contents.. */

Otherwise looks fine:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Patch
diff mbox series

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 55da7e1154f4..d8f209bc8937 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1239,6 +1239,7 @@  xfs_reflink_zero_posteof(
  * Prepare two files for range cloning.  Upon a successful return both inodes
  * will have the iolock and mmaplock held, the page cache of the out file
  * will be truncated, and any leases on the out file will have been broken.
+ * This function borrows heavily from xfs_file_aio_write_checks.
  */
 STATIC int
 xfs_reflink_remap_prep(
@@ -1302,6 +1303,30 @@  xfs_reflink_remap_prep(
 	/* Zap any page cache for the destination file's range. */
 	truncate_inode_pages_range(&inode_out->i_data, pos_out,
 				   PAGE_ALIGN(pos_out + len) - 1);
+
+	/* If we're altering the file contents... */
+	if (!is_dedupe) {
+		/*
+		 * ...update the timestamps (which will grab the ilock again
+		 * from xfs_fs_dirty_inode, so we have to call it before we
+		 * take the ilock).
+		 */
+		if (!(file_out->f_mode & FMODE_NOCMTIME)) {
+			ret = file_update_time(file_out);
+			if (ret)
+				goto out_unlock;
+		}
+
+		/*
+		 * ...clear the security bits if the process is not being run
+		 * by root.  This keeps people from modifying setuid and setgid
+		 * binaries.
+		 */
+		ret = file_remove_privs(file_out);
+		if (ret)
+			goto out_unlock;
+	}
+
 	return 0;
 out_unlock:
 	xfs_reflink_remap_unlock(file_in, file_out);