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From:   Norbert Manthey <nmanthey@amazon.de>
To:     Norbert Manthey <nmanthey@amazon.de>,
        <linux-kernel@vger.kernel.org>
CC:     David Woodhouse <dwmw@amazon.co.uk>,
        Kees Cook <keescook@chromium.org>,
        Anton Vorontsov <anton@enomsg.org>,
        Colin Cross <ccross@android.com>,
        "Tony Luck" <tony.luck@intel.com>
Subject: [PATCH pstore fix v1] pstore: fix use after free
Date:   Fri, 5 Jul 2019 15:06:00 +0200
Message-ID: <1562331960-26198-1-git-send-email-nmanthey@amazon.de>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

The pstore_mkfile() function is passed a pointer to a struct
pstore_record. On success it consumes this 'record' pointer and
references it from the created inode.

On failure, however, it may or may not free the record. There are even
two different code paths which return -ENOMEM -- one of which does and
the other doesn't free the record.

Make the behaviour deterministic by never consuming and freeing the
record when returning failure, allowing the caller to do the cleanup
consistently.

Signed-off-by: Norbert Manthey <nmanthey@amazon.de>

---
 fs/pstore/inode.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -333,7 +333,6 @@ int pstore_mkfile(struct dentry *root, struct pstore_record *record)
 	private = kzalloc(sizeof(*private), GFP_KERNEL);
 	if (!private)
 		goto fail_alloc;
-	private->record = record;
 
 	switch (record->type) {
 	case PSTORE_TYPE_DMESG:
@@ -387,6 +386,8 @@ int pstore_mkfile(struct dentry *root, struct pstore_record *record)
 	if (!dentry)
 		goto fail_private;
 
+	private->record = record;
+
 	inode->i_size = private->total_size = size;
 
 	inode->i_private = private;
-- 
2.7.4


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