From: Ernesto A. Fernández ernesto.mnd.fernandez@gmail.com
[ Upstream commit 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 Signed-off-by: Sasha Levin alexander.levin@microsoft.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 d0f39dcbb58e..2b6e2ad57bf9 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];