]> git.karo-electronics.de Git - karo-tx-linux.git/commit
ovl: fix d_real() for stacked fs
authorMiklos Szeredi <mszeredi@redhat.com>
Tue, 29 Nov 2016 09:20:24 +0000 (10:20 +0100)
committerMiklos Szeredi <mszeredi@redhat.com>
Tue, 29 Nov 2016 09:20:24 +0000 (10:20 +0100)
commitc4fcfc1619ea43a8a89ad2f83ff23905eee088bd
treeabf4c9aeaa627cb0c8b56cd06e0325570f055031
parentbc33b0ca11e3df467777a4fa7639ba488c9d4911
ovl: fix d_real() for stacked fs

Handling of recursion in d_real() is completely broken.  Recursion is only
done in the 'inode != NULL' case.  But when opening the file we have
'inode == NULL' hence d_real() will return an overlay dentry.  This won't
work since overlayfs doesn't define its own file operations, so all file
ops will fail.

Fix by doing the recursion first and the check against the inode second.

Bash script to reproduce the issue written by Quentin:

 - 8< - - - - - 8< - - - - - 8< - - - - - 8< - - - -
tmpdir=$(mktemp -d)
pushd ${tmpdir}

mkdir -p {upper,lower,work}
echo -n 'rocks' > lower/ksplice
mount -t overlay level_zero upper -o lowerdir=lower,upperdir=upper,workdir=work
cat upper/ksplice

tmpdir2=$(mktemp -d)
pushd ${tmpdir2}

mkdir -p {upper,work}
mount -t overlay level_one upper -o lowerdir=${tmpdir}/upper,upperdir=upper,workdir=work
ls -l upper/ksplice
cat upper/ksplice
 - 8< - - - - - 8< - - - - - 8< - - - - - 8< - - - -

Reported-by: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 2d902671ce1c ("vfs: merge .d_select_inode() into .d_real()")
Cc: <stable@vger.kernel.org> # v4.8+
fs/overlayfs/super.c