Re: [PATCH] hfsplus: set attributes inode dirty at correct position

[Edward Adam Davis]

On Wed, 15 Apr 2026 15:11:13 -0700, Viacheslav Dubeyko wrote:
> > Syzbot reported a null-ptr-deref in [1].
> > If the attributes file is not loaded during system mount, a trigger
> > occurs [1] when setxattr is executed in userspace.
> >
> > Move the mark inode dirty operation to a point after the attr_tree has
> > been successfully acquired.
> >
> > [1]
> > KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
> > Call Trace:
> >  hfsplus_setxattr+0x124/0x340 fs/hfsplus/xattr.c:555
> >  hfsplus_trusted_setxattr+0x40/0x60 fs/hfsplus/xattr_trusted.c:30
> >  __vfs_setxattr+0x43c/0x480 fs/xattr.c:218
> >  __vfs_setxattr_noperm+0x12d/0x660 fs/xattr.c:252
> >  vfs_setxattr+0x163/0x360 fs/xattr.c:339
> >  do_setxattr fs/xattr.c:654 [inline]
> >
> > Reported-by: syzbot+bc70a12e438dadba4fb4@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Fixes: ee8422d00b7c ("hfsplus: fix potential Allocation File corruption after fsync")
> > Closes: https://syzkaller.appspot.com/bug?extid=bc70a12e438dadba4fb4
> > Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>
> > ---
> >  fs/hfsplus/xattr.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/hfsplus/xattr.c b/fs/hfsplus/xattr.c
> > index 452a1f9becb2..3e6f45b3259d 100644
> > --- a/fs/hfsplus/xattr.c
> > +++ b/fs/hfsplus/xattr.c
> > @@ -317,12 +317,14 @@ static int hfsplus_create_attributes_file(struct super_block *sb)
> >  		next_node++;
> >  	}
> >
> > -	hfsplus_mark_inode_dirty(HFSPLUS_ATTR_TREE_I(sb), HFSPLUS_I_ATTR_DIRTY);
> 
> It's really strange that xfstests didn't catch the issue. Probably, we need to
> have the specialized HFS+ tests.
> 
> >  	hfsplus_mark_inode_dirty(attr_file, HFSPLUS_I_ATTR_DIRTY);
> >
> >  	sbi->attr_tree = hfs_btree_open(sb, HFSPLUS_ATTR_CNID);
> >  	if (!sbi->attr_tree)
> >  		pr_err("failed to load attributes file\n");
> > +	else
> > +		hfsplus_mark_inode_dirty(HFSPLUS_ATTR_TREE_I(sb),
> > +					 HFSPLUS_I_ATTR_DIRTY);
> 
> As far as I can see, HFSPLUS_ATTR_TREE_I(sb) and attr_file are the same
> entities. Am I right here? :) So, we can simply remove the first
Yes, they point to the same attr inode.
> hfsplus_mark_inode_dirty(). Does it make sense?
Hmm, yes.

Edward
BR