From 898cc19d8af2d6a80a9f2804b0db2e83c5dd8863 Mon Sep 17 00:00:00 2001
From: Amir Goldstein <amir73il@gmail.com>
Date: Tue, 18 Sep 2018 16:34:32 +0300
Subject: [PATCH] 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: 2a92e07edc5e ("ovl: add ovl_write_iter()")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
fs/overlayfs/file.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index aeaefd2a551b0..986313da0c889 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -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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