Commit a7ec7a41 authored Aug 23, 2018 by Ernesto A. Fernández Committed by Linus Torvalds Aug 23, 2018

hfsplus: fix NULL dereference in hfsplus_lookup()

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>

parent 815f0ddb

fs/hfsplus/dir.c

+2 −2

Original line number	Original line	Diff line number	Diff line
	@@ -77,13 +77,13 @@ static struct dentry hfsplus_lookup(struct inode dir, struct dentry *dentry,
	cpu_to_be32(HFSP_HARDLINK_TYPE) &&		cpu_to_be32(HFSP_HARDLINK_TYPE) &&
	entry.file.user_info.fdCreator ==		entry.file.user_info.fdCreator ==
	cpu_to_be32(HFSP_HFSPLUS_CREATOR) &&		cpu_to_be32(HFSP_HFSPLUS_CREATOR) &&
			HFSPLUS_SB(sb)->hidden_dir &&
	(entry.file.create_date ==		(entry.file.create_date ==
	HFSPLUS_I(HFSPLUS_SB(sb)->hidden_dir)->		HFSPLUS_I(HFSPLUS_SB(sb)->hidden_dir)->
	create_date \|\|		create_date \|\|
	entry.file.create_date ==		entry.file.create_date ==
	HFSPLUS_I(d_inode(sb->s_root))->		HFSPLUS_I(d_inode(sb->s_root))->
	create_date) &&		create_date)) {
	HFSPLUS_SB(sb)->hidden_dir) {
	struct qstr str;		struct qstr str;
	char name[32];		char name[32];