On Tue, Apr 12, 2016 at 11:33:03PM +0100, Al Viro wrote:
> On Tue, Apr 12, 2016 at 10:27:20AM -0700, Jaegeuk Kim wrote:
> > This patch updates fscrypto along with the below ext4 crypto change.
> >
> > Fixes: 3d43bcfef5f0 ("ext4 crypto: use dget_parent() in ext4_d_revalidate()")
>
> > static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
> > {
> > - struct inode *dir = d_inode(dentry->d_parent);
> > - struct fscrypt_info *ci = dir->i_crypt_info;
> > + struct dentry *dir;
> > + struct fscrypt_info *ci;
> > int dir_has_key, cached_with_key;
> >
> > - if (!dir->i_sb->s_cop->is_encrypted(dir))
> > + dir = dget_parent(dentry);
> > + if (!d_inode(dir)->i_sb->s_cop->is_encrypted(d_inode(dir))) {
> > + dput(dir);
>
> ... and as soon as you call it from RCU mode, you are screwed.
Thank you for pointing this out.
IIUC, did you mean this?
Thanks,
>From a0ac7972189b7c366720a0b456e39516d622a6d4 Mon Sep 17 00:00:00 2001
From: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
Date: Tue, 12 Apr 2016 16:05:36 -0700
Subject: [PATCH] ext4/fscrypto: avoid RCU lookup in d_revalidate
As Al pointed, d_revalidate should return RCU lookup before using d_inode.
This was originally introduced by:
commit 34286d666230 ("fs: rcu-walk aware d_revalidate method").
Reported-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
---
fs/crypto/crypto.c | 4 ++++
fs/ext4/crypto.c | 4 ++++
2 files changed, 8 insertions(+)
diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
index da70520..2fc8c43 100644
--- a/fs/crypto/crypto.c
+++ b/fs/crypto/crypto.c
@@ -26,6 +26,7 @@
#include <linux/ratelimit.h>
#include <linux/bio.h>
#include <linux/dcache.h>
+#include <linux/namei.h>
#include <linux/fscrypto.h>
#include <linux/ecryptfs.h>
@@ -353,6 +354,9 @@ static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
struct fscrypt_info *ci;
int dir_has_key, cached_with_key;
+ if (flags & LOOKUP_RCU)
+ return -ECHILD;
+
dir = dget_parent(dentry);
if (!d_inode(dir)->i_sb->s_cop->is_encrypted(d_inode(dir))) {
dput(dir);
diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c
index db9ae6e..6a6c273 100644
--- a/fs/ext4/crypto.c
+++ b/fs/ext4/crypto.c
@@ -32,6 +32,7 @@
#include <linux/random.h>
#include <linux/scatterlist.h>
#include <linux/spinlock_types.h>
+#include <linux/namei.h>
#include "ext4_extents.h"
#include "xattr.h"
@@ -482,6 +483,9 @@ static int ext4_d_revalidate(struct dentry *dentry, unsigned int flags)
struct ext4_crypt_info *ci;
int dir_has_key, cached_with_key;
+ if (flags & LOOKUP_RCU)
+ return -ECHILD;
+
dir = dget_parent(dentry);
if (!ext4_encrypted_inode(d_inode(dir))) {
dput(dir);
--
2.6.3
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