hfsplus: fix NULL dereference in hfsplus_lookup() (CVE-2018-14617)

debian/changelog

@@ -14,6 +14,7 @@ linux (4.18.6-2) UNRELEASED; urgency=medium
     (Closes: #887045, #886292)
   * btrfs: relocation: Only remove reloc rb_trees if reloc control has been
     initialized (CVE-2018-14609)
+  * hfsplus: fix NULL dereference in hfsplus_lookup() (CVE-2018-14617)
 
  -- Ben Hutchings <ben@decadent.org.uk>  Sat, 08 Sep 2018 23:24:31 +0100
 

debian/patches/bugfix/all/hfsplus-fix-NULL-dereference-in-hfsplus_lookup.patch

@@ -0,0 +1,56 @@
+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: hfsplus: fix NULL dereference in hfsplus_lookup()
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+Origin: https://git.kernel.org/linus/a7ec7a4193a2eb3b5341243fc0b621c1ac9e4ec4
+
+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
+
+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>
+---
+ 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 c5a70f83dbe7..f37662675c3a 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];
+ 
+-- 
+2.19.0
+

debian/patches/series

@@ -144,6 +144,7 @@ features/all/lockdown/arm64-add-kernel-config-option-to-lock-down-when.patch
 debian/i386-686-pae-pci-set-pci-nobios-by-default.patch
 bugfix/all/Revert-net-increase-fragment-memory-usage-limits.patch
 bugfix/all/btrfs-relocation-Only-remove-reloc-rb_trees-if-reloc.patch
+bugfix/all/hfsplus-fix-NULL-dereference-in-hfsplus_lookup.patch
 
 # Fix exported symbol versions
 bugfix/all/module-disable-matching-missing-version-crc.patch