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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.1 (by Flathub.org) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2026-09-21 at 17:37 +0200, Bruno Produit wrote: > B-tree nodes with a zero reference count remain in the node hash > until > folio reclaim or tree teardown frees them.=C2=A0 The folio release > callbacks > remove nodes while holding hash_lock, but hfs_btree_close() walks and > frees the same hash without that lock.=C2=A0 Reclaim can therefore unhash > and > free a node after close has loaded its pointer, causing a use-after- > free > or double-free.=20 >=20 > The following syzkaller crashes seem to be the same UAF in=20 > {hfs,hfsplus}_btree_close() (or {hfs,hfsplus}_bnode_unhash()) and > follow=20 > the same pattern, but do not contain a reproducer to confirm.=20 >=20 > Detach each node with hfs_bnode_unhash() while holding hash_lock > before > inspecting and freeing it.=C2=A0 Drop the lock before hfs_bnode_free() so > a > large tree is not freed while holding a spinlock.=C2=A0 Apply the same fi= x > to > the matching HFS+ implementation. >=20 > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Reported-by: syzbot+d729df28d933979e017a@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=3Dd729df28d933979e017a > Reported-by: syzbot+2eac7d175baf21e6a5d5@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=3D2eac7d175baf21e6a5d5 > Reported-by: syzbot+7155b2fe09e033c91381@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=3D7155b2fe09e033c91381 > Reported-by: syzbot+adeb387cede15eb11607@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=3Dadeb387cede15eb11607 > Reported-by: syzbot+ae7f2423f3648100506d@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=3Dae7f2423f3648100506d I still don't see Cc: stable@vger.kernel.org here. > Assisted-by: Codex:gpt-5.6-sol > Reported-by: Kyle Zeng > Signed-off-by: Kyle Zeng > Signed-off-by: Bruno Produit > --- > =C2=A0fs/hfs/btree.c=C2=A0=C2=A0=C2=A0=C2=A0 | 7 +++++-- > =C2=A0fs/hfsplus/btree.c | 7 +++++-- > =C2=A02 files changed, 10 insertions(+), 4 deletions(-) >=20 > diff --git a/fs/hfs/btree.c b/fs/hfs/btree.c > index 41b4e8fc9..4f0ddc76e 100644 > --- a/fs/hfs/btree.c > +++ b/fs/hfs/btree.c > @@ -310,14 +310,17 @@ void hfs_btree_close(struct hfs_btree *tree) > =C2=A0 return; > =C2=A0 > =C2=A0 for (i =3D 0; i < NODE_HASH_SIZE; i++) { > + spin_lock(&tree->hash_lock); > =C2=A0 while ((node =3D tree->node_hash[i])) { > - tree->node_hash[i] =3D node->next_hash; > + hfs_bnode_unhash(node); > + spin_unlock(&tree->hash_lock); > =C2=A0 if (atomic_read(&node->refcnt)) > =C2=A0 pr_err("node %d:%d still has %d > user(s)!\n", > =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 node->tree->cnid, node->th= is, > =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 atomic_read(&node->refcnt)= ); > =C2=A0 hfs_bnode_free(node); > - tree->node_hash_cnt--; > + spin_lock(&tree->hash_lock); > =C2=A0 } > + spin_unlock(&tree->hash_lock); > =C2=A0 } > =C2=A0 iput(tree->inode); > diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c > index 2ea8cd565..bd4dbdbc8 100644 > --- a/fs/hfsplus/btree.c > +++ b/fs/hfsplus/btree.c > @@ -417,15 +417,18 @@ void hfs_btree_close(struct hfs_btree *tree) > =C2=A0 return; > =C2=A0 > =C2=A0 for (i =3D 0; i < NODE_HASH_SIZE; i++) { > + spin_lock(&tree->hash_lock); > =C2=A0 while ((node =3D tree->node_hash[i])) { > - tree->node_hash[i] =3D node->next_hash; > + hfs_bnode_unhash(node); > + spin_unlock(&tree->hash_lock); > =C2=A0 if (atomic_read(&node->refcnt)) > =C2=A0 pr_crit("node %d:%d " > =C2=A0 "still has %d > user(s)!\n", > =C2=A0 node->tree->cnid, node- > >this, > =C2=A0 atomic_read(&node->refcnt)); > =C2=A0 hfs_bnode_free(node); > - tree->node_hash_cnt--; > + spin_lock(&tree->hash_lock); > =C2=A0 } > + spin_unlock(&tree->hash_lock); > =C2=A0 } > =C2=A0 iput(tree->inode); I haven't any comments for the fix. But let me run xfstests for the patch (at minimum for HFS+). Thanks, Slava.