RE: [PATCH v2] fs/hfs: fix s_fs_info leak on setup_bdev_super() failure

Viacheslav Dubeyko
2025-11-26T22:30:36Z

On Wed, 2025-11-26 at 17:06 +0100, Mehdi Ben Hadj Khelifa wrote:
> On 11/26/25 2:48 PM, Christian Brauner wrote:
> > On Wed, Nov 19, 2025 at 07:58:21PM +0000, Viacheslav Dubeyko wrote:
> > > On Wed, 2025-11-19 at 08:38 +0100, Mehdi Ben Hadj Khelifa wrote:
> > > > The regression introduced by commit aca740cecbe5 ("fs: open block device
> > > > after superblock creation") allows setup_bdev_super() to fail after a new
> > > > superblock has been allocated by sget_fc(), but before hfs_fill_super()
> > > > takes ownership of the filesystem-specific s_fs_info data.
> > > >
> > > > In that case, hfs_put_super() and the failure paths of hfs_fill_super()
> > > > are never reached, leaving the HFS mdb structures attached to s->s_fs_info
> > > > unreleased.The default kill_block_super() teardown also does not free
> > > > HFS-specific resources, resulting in a memory leak on early mount failure.
> > > >
> > > > Fix this by moving all HFS-specific teardown (hfs_mdb_put()) from
> > > > hfs_put_super() and the hfs_fill_super() failure path into a dedicated
> > > > hfs_kill_sb() implementation. This ensures that both normal unmount and
> > > > early teardown paths (including setup_bdev_super() failure) correctly
> > > > release HFS metadata.
> > > >
> > > > This also preserves the intended layering: generic_shutdown_super()
> > > > handles VFS-side cleanup, while HFS filesystem state is fully destroyed
> > > > afterwards.
> > > >
> > > > Fixes: aca740cecbe5 ("fs: open block device after superblock creation")
> > > > Reported-by: syzbot+ad45f827c88778ff7df6@syzkaller.appspotmail.com
> > > > Closes: https://syzkaller.appspot.com/bug?extid=ad45f827c88778ff7df6
> > > > Tested-by: syzbot+ad45f827c88778ff7df6@syzkaller.appspotmail.com
> > > > Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
> > > > Signed-off-by: Mehdi Ben Hadj Khelifa <mehdi.benhadjkhelifa@gmail.com>
> > > > ---
> > > > ChangeLog:
> > > >
> > > > Changes from v1:
> > > >
> > > > -Changed the patch direction to focus on hfs changes specifically as
> > > > suggested by al viro
> > > >
> > > > Link:https://lore.kernel.org/all/20251114165255.101361-1-mehdi.benhadjkhelifa@gmail.com/
> > > >
> > > > Note:This patch might need some more testing as I only did run selftests
> > > > with no regression, check dmesg output for no regression, run reproducer
> > > > with no bug and test it with syzbot as well.
> > >
> > > Have you run xfstests for the patch? Unfortunately, we have multiple xfstests
> > > failures for HFS now. And you can check the list of known issues here [1]. The
> > > main point of such run of xfstests is to check that maybe some issue(s) could be
> > > fixed by the patch. And, more important that you don't introduce new issues. ;)
> > >
> > > >
> > > > fs/hfs/super.c | 16 ++++++++++++----
> > > > 1 file changed, 12 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/fs/hfs/super.c b/fs/hfs/super.c
> > > > index 47f50fa555a4..06e1c25e47dc 100644
> > > > --- a/fs/hfs/super.c
> > > > +++ b/fs/hfs/super.c
> > > > @@ -49,8 +49,6 @@ static void hfs_put_super(struct super_block *sb)
> > > > {
> > > > cancel_delayed_work_sync(&HFS_SB(sb)->mdb_work);
> > > > hfs_mdb_close(sb);
> > > > - /* release the MDB's resources */
> > > > - hfs_mdb_put(sb);
> > > > }
> > > >
> > > > static void flush_mdb(struct work_struct *work)
> > > > @@ -383,7 +381,6 @@ static int hfs_fill_super(struct super_block *sb, struct fs_context *fc)
> > > > bail_no_root:
> > > > pr_err("get root inode failed\n");
> > > > bail:
> > > > - hfs_mdb_put(sb);
> > > > return res;
> > > > }
> > > >
> > > > @@ -431,10 +428,21 @@ static int hfs_init_fs_context(struct fs_context *fc)
> > > > return 0;
> > > > }
> > > >
> > > > +static void hfs_kill_sb(struct super_block *sb)
> > > > +{
> > > > + generic_shutdown_super(sb);
> > > > + hfs_mdb_put(sb);
> > > > + if (sb->s_bdev) {
> > > > + sync_blockdev(sb->s_bdev);
> > > > + bdev_fput(sb->s_bdev_file);
> > > > + }
> > > > +
> > > > +}
> > > > +
> > > > static struct file_system_type hfs_fs_type = {
> > > > .owner = THIS_MODULE,
> > > > .name = "hfs",
> > > > - .kill_sb = kill_block_super,
> > >
> > > It looks like we have the same issue for the case of HFS+ [2]. Could you please
> > > double check that HFS+ should be fixed too?
> >
> > There's no need to open-code this unless I'm missing something. All you
> > need is the following two patches - untested. Both issues were
> > introduced by the conversion to the new mount api.
> Yes, I don't think open-code is needed here IIUC, also as I mentionned
> before I went by the suggestion of Al Viro in previous replies that's my
> main reason for doing it that way in the first place.
>
> Also me and Slava are working on testing the mentionned patches, Should
> I sent them from my part to the maintainers and mailing lists once
> testing has been done?
>
>

I have run the xfstests on the latest kernel. Everything works as expected:

sudo ./check -g auto
FSTYP -- hfsplus
PLATFORM -- Linux/x86_64 hfsplus-testing-0001 6.18.0-rc7 #97 SMP
PREEMPT_DYNAMIC Tue Nov 25 15:12:42 PST 2025
MKFS_OPTIONS -- /dev/loop51
MOUNT_OPTIONS -- /dev/loop51 /mnt/scratch

generic/001 22s ... 53s
generic/002 17s ... 43s

<skipped>

Failures: generic/003 generic/013 generic/020 generic/034 generic/037
generic/039 generic/040 generic/041 generic/056 generic/057 generic/062
generic/065 generic/066 generic/069 generic/070 generic/073 generic/074
generic/079 generic/091 generic/097 generic/101 generic/104 generic/106
generic/107 generic/113 generic/127 generic/241 generic/258 generic/263
generic/285 generic/321 generic/322 generic/335 generic/336 generic/337
generic/339 generic/341 generic/342 generic/343 generic/348 generic/363
generic/376 generic/377 generic/405 generic/412 generic/418 generic/464
generic/471 generic/475 generic/479 generic/480 generic/481 generic/489
generic/490 generic/498 generic/502 generic/510 generic/523 generic/525
generic/526 generic/527 generic/533 generic/534 generic/535 generic/547
generic/551 generic/552 generic/557 generic/563 generic/564 generic/617
generic/631 generic/637 generic/640 generic/642 generic/647 generic/650
generic/690 generic/728 generic/729 generic/760 generic/764 generic/771
generic/776
Failed 84 of 767 tests

Currently, failures are expected. But I don't see any serious crash, especially,
on every single test.

So, I can apply two patches that Christian shared and test it on my side.

I had impression that Christian has taken the patch for HFS already in his tree.
Am I wrong here? I can take both patches in HFS/HFS+ tree. Let me run xfstests
with applied patches at first.

Thanks,
Slava.