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[162.197.212.70]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-30f0b7bb8fasm13237482eec.1.2026.07.02.16.59.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Jul 2026 16:59:42 -0700 (PDT) Message-ID: Subject: Re: [PATCH] hfs: validate catalog CNIDs before instantiating inodes From: Viacheslav Dubeyko To: David Maximiliano Hermitte , Jori Koolstra Cc: George Anthony Vernon , Tetsuo Handa , John Paul Adrian Glaubitz , Yangtao Li , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+97e301b4b82ae803d21b@syzkaller.appspotmail.com Date: Thu, 02 Jul 2026 16:59:41 -0700 In-Reply-To: <20260702183800.1119202-1-davemadmaxxx@gmail.com> References: <20260702183800.1119202-1-davemadmaxxx@gmail.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 Thu, 2026-07-02 at 18:38 +0000, David Maximiliano Hermitte wrote: > hfs_cat_find_brec() first resolves a catalog thread record by CNID > and > then looks up the corresponding catalog record by parent/name. On a > corrupted filesystem image, the second lookup may find a record whose > CNID does not match the CNID that was requested. >=20 > Validate the catalog record found by the second lookup before > returning > it to callers. Inspect the already-found record with > hfs_bnode_read(), > not hfs_brec_read(), and reject records whose CNID is invalid for > their > record type or does not match the requested CNID. >=20 > Also validate CNIDs in hfs_read_inode() before the inode is > populated, > and propagate hfs_read_inode() errors from the resource-fork lookup > path. > For the root inode path, require the root catalog record to be a > directory > with DirID =3D=3D HFS_ROOT_CNID, and drop the root inode reference if it > was > instantiated as a bad inode. >=20 > This keeps hfs_write_inode() unchanged and prevents corrupted catalog > records from reaching the existing reserved-CNID BUG() path during > writeback. >=20 > Reported-by: syzbot+97e301b4b82ae803d21b@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=3D97e301b4b82ae803d21b > Cc: George Anthony Vernon > Cc: Tetsuo Handa > Signed-off-by: David Maximiliano Hermitte > --- > =C2=A0fs/hfs/catalog.c | 48 > +++++++++++++++++++++++++++++++++++++++++++++++- > =C2=A0fs/hfs/hfs_fs.h=C2=A0 | 19 +++++++++++++++++++ > =C2=A0fs/hfs/inode.c=C2=A0=C2=A0 |=C2=A0 9 ++++++++- > =C2=A0fs/hfs/super.c=C2=A0=C2=A0 |=C2=A0 8 +++++++- > =C2=A04 files changed, 81 insertions(+), 3 deletions(-) >=20 > diff --git a/fs/hfs/catalog.c b/fs/hfs/catalog.c > index 1bfa36d71e24..fa2a0a5975e3 100644 > --- a/fs/hfs/catalog.c > +++ b/fs/hfs/catalog.c > @@ -182,6 +182,47 @@ int hfs_cat_keycmp(const btree_key *key1, const > btree_key *key2) > =C2=A0 =C2=A0 key2->cat.CName.name, key2- > >cat.CName.len); > =C2=A0} > =C2=A0 > +static int hfs_cat_validate_found_cnid(struct hfs_find_data *fd, u32 > cnid) > +{ > + hfs_cat_rec rec; > + u32 found_cnid; > + unsigned int rec_len; I prefer to see the size_t here. > + size_t cnid_off; > + > + if (fd->entrylength <=3D 0) > + return -EIO; > + > + if ((unsigned int)fd->entrylength > sizeof(rec)) The hfs_cat_rec union is big enough to keep any type of record in Catalog File. If fd->entrylength is bigger one, then it sounds like a incorrect behavior or corruption. We cannot silently process such situation. > + rec_len =3D sizeof(rec); > + else > + rec_len =3D fd->entrylength; > + > + memset(&rec, 0, sizeof(rec)); > + hfs_bnode_read(fd->bnode, &rec, fd->entryoffset, rec_len); > + > + switch (rec.type) { > + case HFS_CDR_FIL: > + cnid_off =3D offsetof(struct hfs_cat_file, FlNum); > + if ((size_t)rec_len < cnid_off + > sizeof(rec.file.FlNum)) > + return -EIO; If you would like to check that size of the record, then you don't need to do this weird logic. typedef union hfs_cat_rec { s8 type; /* The type of entry */ struct hfs_cat_file file; struct hfs_cat_dir dir; struct hfs_cat_thread thread; } hfs_cat_rec; You can simply compare with particular structure size. > + found_cnid =3D be32_to_cpu(rec.file.FlNum); > + break; > + case HFS_CDR_DIR: > + cnid_off =3D offsetof(struct hfs_cat_dir, DirID); > + if ((size_t)rec_len < cnid_off + > sizeof(rec.dir.DirID)) > + return -EIO; Ditto. > + found_cnid =3D be32_to_cpu(rec.dir.DirID); > + break; > + default: > + return -EIO; Are we sure that thread record cannot be checked by this logic? > + } > + > + if (!hfs_is_valid_cnid(found_cnid, rec.type) || found_cnid > !=3D cnid) We don't need to call hfs_is_valid_cnid() because found_cnid !=3D cnid is completely enough. > + return -EIO; > + > + return 0; > +} > + > =C2=A0/* Try to get a catalog entry for given catalog id */ > =C2=A0// move to read_super??? > =C2=A0int hfs_cat_find_brec(struct super_block *sb, u32 cnid, > @@ -208,7 +249,12 @@ int hfs_cat_find_brec(struct super_block *sb, > u32 cnid, > =C2=A0 return -EIO; > =C2=A0 } > =C2=A0 memcpy(fd->search_key->cat.CName.name, > rec.thread.CName.name, len); > - return hfs_brec_find(fd); > + > + res =3D hfs_brec_find(fd); > + if (res) > + return res; > + > + return hfs_cat_validate_found_cnid(fd, cnid); > =C2=A0} > =C2=A0 > =C2=A0static inline > diff --git a/fs/hfs/hfs_fs.h b/fs/hfs/hfs_fs.h > index f3624514fcb0..670638f17438 100644 > --- a/fs/hfs/hfs_fs.h > +++ b/fs/hfs/hfs_fs.h > @@ -155,6 +155,25 @@ extern int hfs_cat_move(u32 cnid, struct inode > *src_dir, > =C2=A0extern void hfs_cat_build_key(struct super_block *sb, btree_key > *key, > =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 u32 parent, const struct qstr *na= me); > =C2=A0 > +/* > + * Validate the CNID of a catalog record. > + */ > +static inline bool hfs_is_valid_cnid(u32 cnid, u8 type) > +{ > + if (likely(cnid >=3D HFS_FIRSTUSER_CNID)) > + return true; > + > + switch (cnid) { > + case HFS_ROOT_CNID: > + return type =3D=3D HFS_CDR_DIR; > + case HFS_EXT_CNID: > + case HFS_CAT_CNID: > + return type =3D=3D HFS_CDR_FIL; > + default: > + return false; > + } > +} > + > =C2=A0/* dir.c */ > =C2=A0extern const struct file_operations hfs_dir_operations; > =C2=A0extern const struct inode_operations hfs_dir_inode_operations; > diff --git a/fs/hfs/inode.c b/fs/hfs/inode.c > index ac4a9055c5c0..c685f1bb7009 100644 > --- a/fs/hfs/inode.c > +++ b/fs/hfs/inode.c > @@ -367,6 +367,9 @@ static int hfs_read_inode(struct inode *inode, > void *data) > =C2=A0 rec =3D idata->rec; > =C2=A0 switch (rec->type) { > =C2=A0 case HFS_CDR_FIL: > + if (!hfs_is_valid_cnid(be32_to_cpu(rec->file.FlNum), > rec->type)) > + return -EIO; > + > =C2=A0 if (!HFS_IS_RSRC(inode)) { > =C2=A0 hfs_inode_read_fork(inode, rec->file.ExtRec, > rec->file.LgLen, > =C2=A0 =C2=A0=C2=A0=C2=A0 rec->file.PyLen, > be16_to_cpu(rec->file.ClpSize)); > @@ -390,6 +393,9 @@ static int hfs_read_inode(struct inode *inode, > void *data) > =C2=A0 inode->i_mapping->a_ops =3D &hfs_aops; > =C2=A0 break; > =C2=A0 case HFS_CDR_DIR: > + if (!hfs_is_valid_cnid(be32_to_cpu(rec->dir.DirID), > rec->type)) > + return -EIO; > + > =C2=A0 inode->i_ino =3D be32_to_cpu(rec->dir.DirID); > =C2=A0 inode->i_size =3D be16_to_cpu(rec->dir.Val) + 2; > =C2=A0 HFS_I(inode)->fs_blocks =3D 0; > @@ -571,7 +577,8 @@ static struct dentry *hfs_file_lookup(struct > inode *dir, struct dentry *dentry, > =C2=A0 res =3D hfs_brec_read(&fd, &rec, sizeof(rec)); > =C2=A0 if (!res) { > =C2=A0 struct hfs_iget_data idata =3D { NULL, &rec }; > - hfs_read_inode(inode, &idata); > + Do we really need empty line here? > + res =3D hfs_read_inode(inode, &idata); > =C2=A0 } > =C2=A0 hfs_find_exit(&fd); I believe we need something like this here: if (res || is_bad_inode(inode)) { iput(inode); return ERR_PTR(-EIO); } > =C2=A0 if (res) { > diff --git a/fs/hfs/super.c b/fs/hfs/super.c > index a466c401f6bb..5275936304c7 100644 > --- a/fs/hfs/super.c > +++ b/fs/hfs/super.c > @@ -361,7 +361,8 @@ static int hfs_fill_super(struct super_block *sb, > struct fs_context *fc) > =C2=A0 goto bail_hfs_find; > =C2=A0 } > =C2=A0 hfs_bnode_read(fd.bnode, &rec, fd.entryoffset, > fd.entrylength); > - if (rec.type !=3D HFS_CDR_DIR) > + if (rec.type !=3D HFS_CDR_DIR || > + =C2=A0=C2=A0=C2=A0 be32_to_cpu(rec.dir.DirID) !=3D HFS_ROOT_CNID) This check is completely not necessary here because hfs_cat_validate_found_cnid() will execute the CNID check. Thanks, Slava. > =C2=A0 res =3D -EIO; > =C2=A0 } > =C2=A0 if (res) > @@ -372,6 +373,11 @@ static int hfs_fill_super(struct super_block > *sb, struct fs_context *fc) > =C2=A0 if (!root_inode) > =C2=A0 goto bail_no_root; > =C2=A0 > + if (is_bad_inode(root_inode)) { > + iput(root_inode); > + goto bail_no_root; > + } > + > =C2=A0 set_default_d_op(sb, &hfs_dentry_operations); > =C2=A0 res =3D -ENOMEM; > =C2=A0 sb->s_root =3D d_make_root(root_inode);