Commit 898cc19d authored Sep 18, 2018 by Amir Goldstein Committed by Miklos Szeredi Sep 24, 2018

ovl: fix freeze protection bypass in ovl_write_iter()



Tested by re-writing to an open overlayfs file while upper ext4 is frozen:

  xfs_io -f /ovl/x
  xfs_io> pwrite 0 4096
                             fsfreeze -f /ext4
  xfs_io> pwrite 0 4096

  WARNING: CPU: 0 PID: 1492 at fs/ext4/ext4_jbd2.c:53 \
           ext4_journal_check_start+0x48/0x82

After the fix, the second write blocks in ovl_write_iter() and avoids
hitting WARN_ON(sb->s_writers.frozen == SB_FREEZE_COMPLETE) in
ext4_journal_check_start().

Fixes: 2a92e07e ("ovl: add ovl_write_iter()")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

parent 63e13252

fs/overlayfs/file.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -240,8 +240,10 @@ static ssize_t ovl_write_iter(struct kiocb iocb, struct iov_iter iter)
		goto out_unlock;

		old_cred = ovl_override_creds(file_inode(file)->i_sb);
		file_start_write(real.file);
		ret = vfs_iter_write(real.file, iter, &iocb->ki_pos,
		ovl_iocb_to_rwf(iocb));
		file_end_write(real.file);
		revert_creds(old_cred);

		/* Update size */

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