| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.6 188/203] ovl: verify upper dentry in ovl_remove_and_whiteout() | Date | Mon, 25 Jul 2016 13:56:43 -0700 |
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4.6-stable review patch. If anyone has any objections, please let me know.
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From: Maxim Patlasov <mpatlasov@virtuozzo.com>
commit cfc9fde0b07c3b44b570057c5f93dda59dca1c94 upstream.
The upper dentry may become stale before we call ovl_lock_rename_workdir. For example, someone could (mistakenly or maliciously) manually unlink(2) it directly from upperdir.
To ensure it is not stale, let's lookup it after ovl_lock_rename_workdir and and check if it matches the upper dentry.
Essentially, it is the same problem and similar solution as in commit 11f3710417d0 ("ovl: verify upper dentry before unlink and rename").
Signed-off-by: Maxim Patlasov <mpatlasov@virtuozzo.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- fs/overlayfs/dir.c | 56 +++++++++++++++++++++++------------------------------ 1 file changed, 25 insertions(+), 31 deletions(-)
--- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -511,6 +511,7 @@ static int ovl_remove_and_whiteout(struc struct dentry *upper; struct dentry *opaquedir = NULL; int err; + int flags = 0; if (WARN_ON(!workdir)) return -EROFS; @@ -540,46 +541,39 @@ static int ovl_remove_and_whiteout(struc if (err) goto out_dput; + upper = lookup_one_len(dentry->d_name.name, upperdir, + dentry->d_name.len); + err = PTR_ERR(upper); + if (IS_ERR(upper)) + goto out_unlock; + + err = -ESTALE; + if ((opaquedir && upper != opaquedir) || + (!opaquedir && ovl_dentry_upper(dentry) && + upper != ovl_dentry_upper(dentry))) { + goto out_dput_upper; + } + whiteout = ovl_whiteout(workdir, dentry); err = PTR_ERR(whiteout); if (IS_ERR(whiteout)) - goto out_unlock; + goto out_dput_upper; - upper = ovl_dentry_upper(dentry); - if (!upper) { - upper = lookup_one_len(dentry->d_name.name, upperdir, - dentry->d_name.len); - err = PTR_ERR(upper); - if (IS_ERR(upper)) - goto kill_whiteout; - - err = ovl_do_rename(wdir, whiteout, udir, upper, 0); - dput(upper); - if (err) - goto kill_whiteout; - } else { - int flags = 0; - - if (opaquedir) - upper = opaquedir; - err = -ESTALE; - if (upper->d_parent != upperdir) - goto kill_whiteout; - - if (is_dir) - flags |= RENAME_EXCHANGE; - - err = ovl_do_rename(wdir, whiteout, udir, upper, flags); - if (err) - goto kill_whiteout; + if (d_is_dir(upper)) + flags = RENAME_EXCHANGE; + + err = ovl_do_rename(wdir, whiteout, udir, upper, flags); + if (err) + goto kill_whiteout; + if (flags) + ovl_cleanup(wdir, upper); - if (is_dir) - ovl_cleanup(wdir, upper); - } ovl_dentry_version_inc(dentry->d_parent); out_d_drop: d_drop(dentry); dput(whiteout); +out_dput_upper: + dput(upper); out_unlock: unlock_rename(workdir, upperdir); out_dput:
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