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Mon, 15 Jun 2026 23:29:54 -0700 (PDT) Message-ID: <52bae72d5ca54eed5b4f2218fca124e5bbb0747a.camel@dubeyko.com> Subject: Re: HFS syzbot BUG: test patch validating metadata before hfs_write_inode() From: Viacheslav Dubeyko To: David Maximiliano Hermitte Cc: John Paul Adrian Glaubitz , Yangtao Li , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Mon, 15 Jun 2026 23:29:50 -0700 In-Reply-To: <20260612162043.1524591-1-davemadmaxxx@gmail.com> References: <20260612162043.1524591-1-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 Hi David, On Fri, 2026-06-12 at 16:20 +0000, David Maximiliano Hermitte wrote: > Hi Slava, >=20 > I followed the direction you pointed out and tested a small HFS > validation patch for the syzbot crash path. >=20 > This is not intended as a final upstream patch yet. I am sending it > as a test patch to demonstrate the crash direction and to ask whether > this is the right validation point. If the direction is correct, I > would appreciate guidance on the preferred upstream placement and > syntax before a formal submission. >=20 > My understanding is that the BUG() in hfs_write_inode() is the > endpoint, not the root cause. This test patch keeps hfs_write_inode() > intact and rejects corrupted HFS metadata earlier in hfs_read_inode() > and hfs_brec_read(). >=20 > Local QEMU result: >=20 > BEFORE_UNPATCHED: > - repro_started=3Dtrue > - kernel_bug_seen=3Dtrue > - verdict=3DBEFORE_BUG_REPRODUCED >=20 > AFTER_V04_PATCHED: > - repro_started=3Dtrue > - clean_hfs_rejects=3D50 > - kernel_bug=3DFalse > - oops=3DFalse > - kasan=3DFalse > - hfs_write_inode=3DFalse > - verdict=3DAFTER_REPRO_RAN_NO_BUG_SEEN >=20 > checkpatch.pl --strict: > - 0 errors, 0 warnings >=20 > The test patch is included below inline. Full QEMU serial logs are > available if useful. >=20 > Please let me know whether this validation direction matches what you > expect, or whether the fix should be placed differently. >=20 Sorry, I am in personal trip right now. And I have not much time and capabilities for deep review and discussion. I am going to be back to normal routine around June 26th. I hope our discussion and fix can wait two weeks. :) Could you please ping me and revive the discussion around that time? Thanks, Slava. > Best regards, > David >=20 > --- test patch follows --- >=20 > diff --git a/fs/hfs/bfind.c b/fs/hfs/bfind.c > index d56e47b..5f56cab 100644 > --- a/fs/hfs/bfind.c > +++ b/fs/hfs/bfind.c > @@ -174,8 +174,10 @@ int hfs_brec_read(struct hfs_find_data *fd, void > *rec, u32 rec_len) > =C2=A0 res =3D hfs_brec_find(fd); > =C2=A0 if (res) > =C2=A0 return res; > + if (fd->entryoffset < 0 || fd->entrylength <=3D 0) > + return -EFSCORRUPTED; > =C2=A0 if (fd->entrylength > rec_len) > - return -EINVAL; > + return -EFSCORRUPTED; > =C2=A0 hfs_bnode_read(fd->bnode, rec, fd->entryoffset, fd- > >entrylength); > =C2=A0 return 0; > =C2=A0} > diff --git a/fs/hfs/inode.c b/fs/hfs/inode.c > index 878535d..beefb47 100644 > --- a/fs/hfs/inode.c > +++ b/fs/hfs/inode.c > @@ -369,6 +369,8 @@ 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 (be32_to_cpu(rec->file.FlNum) < > HFS_FIRSTUSER_CNID) > + return -EFSCORRUPTED; > =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 +392,9 @@ 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 (be32_to_cpu(rec->dir.DirID) < HFS_FIRSTUSER_CNID > && > + =C2=A0=C2=A0=C2=A0 be32_to_cpu(rec->dir.DirID) !=3D HFS_ROOT_CNID) > + return -EFSCORRUPTED; > =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;