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([2600:1700:6476:1430:9da4:6df:559d:f4cd]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-6740ef87db6sm5265370d50.17.2026.09.28.13.57.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Sep 2026 13:57:02 -0700 (PDT) Message-ID: Subject: Re: [PATCH 1/2] hfs: bound the partition-table hop in hfs_mdb_get() From: Viacheslav Dubeyko To: Matthias Goergens Cc: John Paul Adrian Glaubitz , Yangtao Li , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Mon, 28 Sep 2026 13:57:01 -0700 In-Reply-To: <20260926084010.569552-2-matthias.goergens@gmail.com> References: <20260926084010.569552-1-matthias.goergens@gmail.com> <20260926084010.569552-2-matthias.goergens@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 Sat, 2026-09-26 at 16:40 +0800, Matthias Goergens wrote: > hfs_mdb_get() loops "while (1)" around hfs_part_find(), rereading the > volume header wherever the partition table points.=C2=A0 A partition entr= y > with a zero start (pdStart or pmPyPartStart) leaves part_start where > it > was, and the loop reads the same blocks forever. >=20 > An Apple partition map sits at the start of the raw device: the boot > ROM > reads it from block 1 (TN1189), and nothing Apple documents nests one > inside a partition.=C2=A0 Follow at most one partition-table hop and fail > with -EIO after that, as for a table that cannot be parsed.=C2=A0 A zero > start is caught on the second pass, when the loop comes round again. >=20 > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Cc: stable@vger.kernel.org > Signed-off-by: Matthias Goergens > --- > A partition entry pointing at its own table hangs the mount forever > without this patch and fails at once with it: >=20 > =C2=A0 img=3Dhfs-partmap-loop.img > =C2=A0 put() { printf "$2" | dd of=3D$img bs=3D1 seek=3D$1 conv=3Dnotrunc > status=3Dnone; } > =C2=A0 truncate --size=3D64K $img > =C2=A0 put $((512+0x00)) '\x50\x4d'=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0 # pmSig 'PM' > =C2=A0 put $((512+0x04)) '\x00\x00\x00\x01'=C2=A0 # pmMapBlkCnt 1 > =C2=A0 put $((512+0x08)) '\x00\x00\x00\x00'=C2=A0 # pmPyPartStart 0 (self= ) > =C2=A0 put $((512+0x0c)) '\x00\x00\x00\x64'=C2=A0 # pmPartBlkCnt 100 > =C2=A0 put $((512+0x30)) 'Apple_HFS'=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0 # pmPartType > =C2=A0 mount -o ro,loop -t hfs $img /mnt > --- > =C2=A0fs/hfs/mdb.c | 10 +++++++++- > =C2=A01 file changed, 9 insertions(+), 1 deletion(-) >=20 > diff --git a/fs/hfs/mdb.c b/fs/hfs/mdb.c > index 277de712f9d4..1704f332e28d 100644 > --- a/fs/hfs/mdb.c > +++ b/fs/hfs/mdb.c > @@ -134,6 +134,7 @@ int hfs_mdb_get(struct super_block *sb) > =C2=A0 sector_t part_start, part_size; > =C2=A0 loff_t off; > =C2=A0 __be16 attrib; > + bool part_hop_done =3D false; > =C2=A0 > =C2=A0 /* set the device driver to 512-byte blocks */ > =C2=A0 size =3D sb_min_blocksize(sb, HFS_SECTOR_SIZE); > @@ -152,11 +153,18 @@ int hfs_mdb_get(struct super_block *sb) > =C2=A0 break; > =C2=A0 brelse(bh); > =C2=A0 > - /* check for a partition block > + /* > + * check for a partition block > =C2=A0 * (should do this only for cdrom/loop though) > + * > + * The partition map is at the start of the device: > follow > + * it once, or an entry pointing at itself loops > forever. > =C2=A0 */ > + if (part_hop_done) > + return -EIO; > =C2=A0 if (hfs_part_find(sb, &part_start, &part_size)) If I understood the problem correctly, then we have issue in hfs_part_find(). This method should have the proper sanity check. Thanks, Slava. > =C2=A0 return -EIO; > + part_hop_done =3D true; > =C2=A0 } > =C2=A0 > =C2=A0 HFS_SB(sb)->alloc_blksz =3D size =3D be32_to_cpu(mdb- > >drAlBlkSiz); >=20 > base-commit: 6812ce4e4379ffc99c52401ec28f0d7ffbc36206