This is a note to let you know that I've just added the patch titled ubifs: Fix O_TMPFILE corner case in ubifs_link() to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: ubifs-fix-o_tmpfile-corner-case-in-ubifs_link.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 32fe905c17f001c0eee13c59afddd0bf2eed509c Mon Sep 17 00:00:00 2001 From: Richard Weinberger <richard@xxxxxx> Date: Thu, 30 Mar 2017 10:50:49 +0200 Subject: ubifs: Fix O_TMPFILE corner case in ubifs_link() From: Richard Weinberger <richard@xxxxxx> commit 32fe905c17f001c0eee13c59afddd0bf2eed509c upstream. 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. Ralph faced a filesystem corruption in combination with overlayfs due to this bug. Cc: Ralph Sennhauser <ralph.sennhauser@xxxxxxxxx> Cc: Amir Goldstein <amir73il@xxxxxxxxx> Reported-by: Ralph Sennhauser <ralph.sennhauser@xxxxxxxxx> Tested-by: Ralph Sennhauser <ralph.sennhauser@xxxxxxxxx> Reported-by: Amir Goldstein <amir73il@xxxxxxxxx> Fixes: 474b93704f321 ("ubifs: Implement O_TMPFILE") Signed-off-by: Richard Weinberger <richard@xxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/ubifs/dir.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/fs/ubifs/dir.c +++ b/fs/ubifs/dir.c @@ -622,6 +622,11 @@ static int ubifs_link(struct dentry *old return err; 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); @@ -641,6 +646,8 @@ out_cancel: dir->i_size -= sz_change; dir_ui->ui_size = dir->i_size; drop_nlink(inode); + if (inode->i_nlink == 0) + ubifs_add_orphan(c, inode->i_ino); unlock_2_inodes(dir, inode); ubifs_release_budget(c, &req); iput(inode); Patches currently in stable-queue which might be from richard@xxxxxx are queue-4.9/ubifs-fix-rename_whiteout-support.patch queue-4.9/ubi-upd-always-flush-after-prepared-for-an-update.patch queue-4.9/ubifs-fix-o_tmpfile-corner-case-in-ubifs_link.patch