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From a7ec7a4193a2eb3b5341243fc0b621c1ac9e4ec4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ernesto=20A=2E=20Fern=C3=A1ndez?=
<ernesto.mnd.fernandez@gmail.com>
Date: Thu, 23 Aug 2018 17:00:25 -0700
Subject: [PATCH] hfsplus: fix NULL dereference in hfsplus_lookup()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
An HFS+ filesystem can be mounted read-only without having a metadata
directory, which is needed to support hardlinks. But if the catalog
data is corrupted, a directory lookup may still find dentries claiming
to be hardlinks.
hfsplus_lookup() does check that ->hidden_dir is not NULL in such a
situation, but mistakenly does so after dereferencing it for the first
time. Reorder this check to prevent a crash.
This happens when looking up corrupted catalog data (dentry) on a
filesystem with no metadata directory (this could only ever happen on a
read-only mount). Wen Xu sent the replication steps in detail to the
fsdevel list: https://bugzilla.kernel.org/show_bug.cgi?id=200297
CVE: CVE-2018-14617
Upstream-Status: Backport
Link: http://lkml.kernel.org/r/20180712215344.q44dyrhymm4ajkao@eaf
Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Reported-by: Wen Xu <wen.xu@gatech.edu>
Cc: Viacheslav Dubeyko <slava@dubeyko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
---
fs/hfsplus/dir.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/hfsplus/dir.c b/fs/hfsplus/dir.c
index c5a70f8..f376626 100644
--- a/fs/hfsplus/dir.c
+++ b/fs/hfsplus/dir.c
@@ -77,13 +77,13 @@ static struct dentry *hfsplus_lookup(struct inode *dir, struct dentry *dentry,
cpu_to_be32(HFSP_HARDLINK_TYPE) &&
entry.file.user_info.fdCreator ==
cpu_to_be32(HFSP_HFSPLUS_CREATOR) &&
+ HFSPLUS_SB(sb)->hidden_dir &&
(entry.file.create_date ==
HFSPLUS_I(HFSPLUS_SB(sb)->hidden_dir)->
create_date ||
entry.file.create_date ==
HFSPLUS_I(d_inode(sb->s_root))->
- create_date) &&
- HFSPLUS_SB(sb)->hidden_dir) {
+ create_date)) {
struct qstr str;
char name[32];
--
2.7.4
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