linux-kernel - [PATCH] ubifs: Fix O_TMPFILE corner case in ubifs

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Date:   Thu, 30 Mar 2017 10:56:21 +0200
From:   Richard Weinberger <richard@....at>
To:     linux-mtd@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, adrian.hunter@...el.com,
        dedekind1@...il.com, richard@....at, stable@...r.kernel.org,
        Ralph Sennhauser <ralph.sennhauser@...il.com>,
        Amir Goldstein <amir73il@...il.com>
Subject: [PATCH] ubifs: Fix O_TMPFILE corner case in ubifs_link()

It is perfectly fine to link a tmpfile back using linkat().
Since tmpfiles are created with a link count of 0 they appear
on the orphan list, upon re-linking the inode has to be removed
from the orphan list again.

Cc: <stable@...r.kernel.org>
Cc: Ralph Sennhauser <ralph.sennhauser@...il.com>
Cc: Amir Goldstein <amir73il@...il.com
Reported-by: Ralph Sennhauser <ralph.sennhauser@...il.com>
Tested-by: Ralph Sennhauser <ralph.sennhauser@...il.com>
Reported-by: Amir Goldstein <amir73il@...il.com
Fixes: 474b93704f321 ("ubifs: Implement O_TMPFILE")
Signed-off-by: Richard Weinberger <richard@....at>
---
 fs/ubifs/dir.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
index 0858213a4e63..0139155045fe 100644
--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -748,6 +748,11 @@ static int ubifs_link(struct dentry *old_dentry, struct inode *dir,
 		goto out_fname;
 
 	lock_2_inodes(dir, inode);
+
+	/* Handle O_TMPFILE corner case, it is allowed to link a O_TMPFILE. */
+	if (inode->i_nlink == 0)
+		ubifs_delete_orphan(c, inode->i_ino);
+
 	inc_nlink(inode);
 	ihold(inode);
 	inode->i_ctime = ubifs_current_time(inode);
-- 
2.7.3