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([2600:1700:6476:1430:af0a:8535:f1b1:7cb0]) by smtp.gmail.com with ESMTPSA id 00721157ae682-8a4667cffc0sm3182727b3.43.2026.09.22.15.38.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Sep 2026 15:39:00 -0700 (PDT) Message-ID: Subject: Re: [PATCH v2] hfs/hfsplus: serialize B-tree close against folio release From: Viacheslav Dubeyko To: Bruno Produit , John Paul Adrian Glaubitz , Yangtao Li Cc: Kyle Zeng , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Dominik Czarnota , stable@vger.kernel.org, syzbot+d729df28d933979e017a@syzkaller.appspotmail.com, syzbot+2eac7d175baf21e6a5d5@syzkaller.appspotmail.com, syzbot+7155b2fe09e033c91381@syzkaller.appspotmail.com, syzbot+adeb387cede15eb11607@syzkaller.appspotmail.com, syzbot+ae7f2423f3648100506d@syzkaller.appspotmail.com Date: Tue, 22 Sep 2026 15:38:58 -0700 In-Reply-To: References: <20260921153729.600313-1-bruno.produit@trailofbits.com> Autocrypt: addr=slava@dubeyko.com; prefer-encrypt=mutual; keydata=mQINBGgaTLYBEADaJc/WqWTeunGetXyyGJ5Za7b23M/ozuDCWCp+yWUa2GqQKH40dxRIR zshgOmAue7t9RQJU9lxZ4ZHWbi1Hzz85+0omefEdAKFmxTO6+CYV0g/sapU0wPJws3sC2Pbda9/eJ ZcvScAX2n/PlhpTnzJKf3JkHh3nM1ACO3jzSe2/muSQJvqMLG2D71ccekr1RyUh8V+OZdrPtfkDam V6GOT6IvyE+d+55fzmo20nJKecvbyvdikWwZvjjCENsG9qOf3TcCJ9DDYwjyYe1To8b+mQM9nHcxp jUsUuH074BhISFwt99/htZdSgp4csiGeXr8f9BEotRB6+kjMBHaiJ6B7BIlDmlffyR4f3oR/5hxgy dvIxMocqyc03xVyM6tA4ZrshKkwDgZIFEKkx37ec22ZJczNwGywKQW2TGXUTZVbdooiG4tXbRBLxe ga/NTZ52ZdEkSxAUGw/l0y0InTtdDIWvfUT+WXtQcEPRBE6HHhoeFehLzWL/o7w5Hog+0hXhNjqte fzKpI2fWmYzoIb6ueNmE/8sP9fWXo6Av9m8B5hRvF/hVWfEysr/2LSqN+xjt9NEbg8WNRMLy/Y0MS p5fgf9pmGF78waFiBvgZIQNuQnHrM+0BmYOhR0JKoHjt7r5wLyNiKFc8b7xXndyCDYfniO3ljbr0j tXWRGxx4to6FwARAQABtCZWaWFjaGVzbGF2IER1YmV5a28gPHNsYXZhQGR1YmV5a28uY29tPokCVw QTAQoAQQIbAQUJA8JnAAULCQgHAgYVCgkICwIEFgIDAQIeAQIXgBYhBFXDC2tnzsoLQtrbBDlc2cL fhEB1BQJoGl5PAhkBAAoJEDlc2cLfhEB17DsP/jy/Dx19MtxWOniPqpQf2s65enkDZuMIQ94jSg7B F2qTKIbNR9SmsczjyjC+/J7m7WZRmcqnwFYMOyNfh12aF2WhjT7p5xEAbvfGVYwUpUrg/lcacdT0D Yk61GGc5ZB89OAWHLr0FJjI54bd7kn7E/JRQF4dqNsxU8qcPXQ0wLHxTHUPZu/w5Zu/cO+lQ3H0Pj pSEGaTAh+tBYGSvQ4YPYBcV8+qjTxzeNwkw4ARza8EjTwWKP2jWAfA/ay4VobRfqNQ2zLoo84qDtN Uxe0zPE2wobIXELWkbuW/6hoQFPpMlJWz+mbvVms57NAA1HO8F5c1SLFaJ6dN0AQbxrHi45/cQXla 9hSEOJjxcEnJG/ZmcomYHFneM9K1p1K6HcGajiY2BFWkVet9vuHygkLWXVYZ0lr1paLFR52S7T+cf 6dkxOqu1ZiRegvFoyzBUzlLh/elgp3tWUfG2VmJD3lGpB3m5ZhwQ3rFpK8A7cKzgKjwPp61Me0o9z HX53THoG+QG+o0nnIKK7M8+coToTSyznYoq9C3eKeM/J97x9+h9tbizaeUQvWzQOgG8myUJ5u5Dr4 6tv9KXrOJy0iy/dcyreMYV5lwODaFfOeA4Lbnn5vRn9OjuMg1PFhCi3yMI4lA4umXFw0V2/OI5rgW BQELhfvW6mxkihkl6KLZX8m1zcHitCpWaWFjaGVzbGF2IER1YmV5a28gPFNsYXZhLkR1YmV5a29Aa WJtLmNvbT6JAlQEEwEKAD4WIQRVwwtrZ87KC0La2wQ5XNnC34RAdQUCaBpd7AIbAQUJA8JnAAULCQ gHAgYVCgkICwIEFgIDAQIeAQIXgAAKCRA5XNnC34RAdYjFEACiWBEybMt1xjRbEgaZ3UP5i2bSway DwYDvgWW5EbRP7JcqOcZ2vkJwrK3gsqC3FKpjOPh7ecE0I4vrabH1Qobe2N8B2Y396z24mGnkTBbb 16Uz3PC93nFN1BA0wuOjlr1/oOTy5gBY563vybhnXPfSEUcXRd28jI7z8tRyzXh2tL8ZLdv1u4vQ8 E0O7lVJ55p9yGxbwgb5vXU4T2irqRKLxRvU80rZIXoEM7zLf5r7RaRxgwjTKdu6rYMUOfoyEQQZTD 4Xg9YE/X8pZzcbYFs4IlscyK6cXU0pjwr2ssjearOLLDJ7ygvfOiOuCZL+6zHRunLwq2JH/RmwuLV mWWSbgosZD6c5+wu6DxV15y7zZaR3NFPOR5ErpCFUorKzBO1nA4dwOAbNym9OGkhRgLAyxwpea0V0 ZlStfp0kfVaSZYo7PXd8Bbtyjali0niBjPpEVZdgtVUpBlPr97jBYZ+L5GF3hd6WJFbEYgj+5Af7C UjbX9DHweGQ/tdXWRnJHRzorxzjOS3003ddRnPtQDDN3Z/XzdAZwQAs0RqqXrTeeJrLppFUbAP+HZ TyOLVJcAAlVQROoq8PbM3ZKIaOygjj6Yw0emJi1D9OsN2UKjoe4W185vamFWX4Ba41jmCPrYJWAWH fAMjjkInIPg7RLGs8FiwxfcpkILP0YbVWHiNAabQoVmlhY2hlc2xhdiBEdWJleWtvIDx2ZHViZXlr b0BrZXJuZWwub3JnPokCVAQTAQoAPhYhBFXDC2tnzsoLQtrbBDlc2cLfhEB1BQJoVemuAhsBBQkDw mcABQsJCAcCBhUKCQgLAgQWAgMBAh4BAheAAAoJEDlc2cLfhEB1GRwP/1scX5HO9Sk7dRicLD/fxo ipwEs+UbeA0/TM8OQfdRI4C/tFBYbQCR7lD05dfq8VsYLEyrgeLqP/iRhabLky8LTaEdwoAqPDc/O 9HRffx/faJZqkKc1dZryjqS6b8NExhKOVWmDqN357+Cl/H4hT9wnvjCj1YEqXIxSd/2Pc8+yw/KRC AP7jtRzXHcc/49Lpz/NU5irScusxy2GLKa5o/13jFK3F1fWX1wsOJF8NlTx3rLtBy4GWHITwkBmu8 zI4qcJGp7eudI0l4xmIKKQWanEhVdzBm5UnfyLIa7gQ2T48UbxJlWnMhLxMPrxgtC4Kos1G3zovEy Ep+fJN7D1pwN9aR36jVKvRsX7V4leIDWGzCdfw1FGWkMUfrRwgIl6i3wgqcCP6r9YSWVQYXdmwdMu 1RFLC44iF9340S0hw9+30yGP8TWwd1mm8V/+zsdDAFAoAwisi5QLLkQnEsJSgLzJ9daAsE8KjMthv hUWHdpiUSjyCpigT+KPl9YunZhyrC1jZXERCDPCQVYgaPt+Xbhdjcem/ykv8UVIDAGVXjuk4OW8la nf8SP+uxkTTDKcPHOa5rYRaeNj7T/NClRSd4z6aV3F6pKEJnEGvv/DFMXtSHlbylhyiGKN2Amd0b4 9jg+DW85oNN7q2UYzYuPwkHsFFq5iyF1QggiwYYTpoVXsw Content-Type: text/plain; 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 12:51 -0700, Viacheslav Dubeyko wrote: > 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 > > fix > > 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 >=20 > I still don't see Cc: stable@vger.kernel.org=C2=A0here. >=20 > > 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- > > >this, > > =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); >=20 > I haven't any comments for the fix. But let me run xfstests for the > patch (at minimum for HFS+). >=20 >=20 I don't see any xfstests degradation for the case of HFS+. The patch looks good. Reviewed-by: Viacheslav Dubeyko Tested-by: Viacheslav Dubeyko Thanks, Slava.