This is a note to let you know that I've just added the patch titled
ovl: verify upper dentry in ovl_remove_and_whiteout()
to the 4.6-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:
ovl-verify-upper-dentry-in-ovl_remove_and_whiteout.patch
and it can be found in the queue-4.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From cfc9fde0b07c3b44b570057c5f93dda59dca1c94 Mon Sep 17 00:00:00 2001
From: Maxim Patlasov <mpatlasov@xxxxxxxxxxxxx>
Date: Thu, 21 Jul 2016 18:24:26 -0700
Subject: ovl: verify upper dentry in ovl_remove_and_whiteout()
From: Maxim Patlasov <mpatlasov@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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:
Patches currently in stable-queue which might be from mpatlasov@xxxxxxxxxxxxx are
queue-4.6/ovl-verify-upper-dentry-in-ovl_remove_and_whiteout.patch
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