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([2600:1700:6476:1430:3705:6d89:7b16:2a59]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-6681fe46cd8sm1082059d50.15.2026.07.15.10.37.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Jul 2026 10:37:34 -0700 (PDT) Message-ID: <771aefbfbf18e60ee6c36698dece92c082a9a389.camel@dubeyko.com> Subject: Re: [PATCH v5] hfs: port HFS+ b-tree bitmap corruption check From: Viacheslav Dubeyko To: Aditya Prakash Srivastava Cc: glaubitz@physik.fu-berlin.de, frank.li@vivo.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 15 Jul 2026 10:37:32 -0700 In-Reply-To: <20260715033829.1698-1-aditya.ansh182@gmail.com> References: <20260715033829.1698-1-aditya.ansh182@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 Wed, 2026-07-15 at 03:38 +0000, Aditya Prakash Srivastava wrote: > In HFS+ filesystems, during b-tree open (hfs_btree_open()), the code > verifies that the allocation map bit for the tree header (node 0) is > set. If not, it indicates a corrupted map record/bitmap and mounts > the volume as read-only (SB_RDONLY) to prevent further damage. >=20 > HFS filesystems share the same b-tree structure but currently lack > this corruption detection check. >=20 > Port this check to HFS, aligning its implementation with HFS+ to > maintain consistent b-tree logic across both filesystems: > 1. Define struct hfs_bmap_ctx, and define HFS_TREE_HEAD and the > relevant > =C2=A0=C2=A0 map record indices in include/linux/hfs_common.h. > 2. Implement static hfs_bmap_get_map_page() in fs/hfs/btree.c, and > port > =C2=A0=C2=A0 the necessary offset and length validation helpers to > fs/hfs/btree.h > =C2=A0=C2=A0 as static inline functions with robust null pointer checks. > 3. Implement static hfs_bmap_test_bit() in fs/hfs/btree.c to inspect > =C2=A0=C2=A0 the B-tree bitmap using the new get_map_page helper. > 4. In hfs_btree_open(), retrieve the header node via > hfs_bnode_find(), > =C2=A0=C2=A0 test its allocation bit with hfs_bmap_test_bit(), and releas= e it > =C2=A0=C2=A0 using hfs_bnode_put(). >=20 > Suggested-by: Viacheslav Dubeyko > Link: > https://lore.kernel.org/all/6a36101b.be22b350.2a3e9.0001.GAE@google.com/T= /#r446d0fed2a2900bd805534bbcb799d86619ae2ea > Signed-off-by: Aditya Prakash Srivastava > --- > =C2=A0fs/hfs/bnode.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0 | 42 ------------------- > =C2=A0fs/hfs/btree.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0 | 84 > ++++++++++++++++++++++++++++++++++++++ > =C2=A0fs/hfs/btree.h=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0 | 40 ++++++++++++++++++ > =C2=A0include/linux/hfs_common.h | 13 ++++-- > =C2=A04 files changed, 134 insertions(+), 45 deletions(-) >=20 > diff --git a/fs/hfs/bnode.c b/fs/hfs/bnode.c > index da8e5342c91c..1b331108d9c0 100644 > --- a/fs/hfs/bnode.c > +++ b/fs/hfs/bnode.c > @@ -15,48 +15,6 @@ > =C2=A0 > =C2=A0#include "btree.h" > =C2=A0 > -static inline > -bool is_bnode_offset_valid(struct hfs_bnode *node, u32 off) > -{ > - bool is_valid =3D off < node->tree->node_size; > - > - if (!is_valid) { > - pr_err("requested invalid offset: " > - =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 "NODE: id %u, type %#x, height %u= , " > - =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 "node_size %u, offset %u\n", > - =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 node->this, node->type, node->hei= ght, > - =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 node->tree->node_size, off); > - } > - > - return is_valid; > -} > - > -static inline > -u32 check_and_correct_requested_length(struct hfs_bnode *node, u32 > off, u32 len) > -{ > - unsigned int node_size; > - > - if (!is_bnode_offset_valid(node, off)) > - return 0; > - > - node_size =3D node->tree->node_size; > - > - if ((u64)off + len > node_size) { > - u32 new_len =3D node_size - off; > - > - pr_err("requested length has been corrected: " > - =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 "NODE: id %u, type %#x, height %u= , " > - =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 "node_size %u, offset %u, " > - =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 "requested_len %u, corrected_len = %u\n", > - =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 node->this, node->type, node->hei= ght, > - =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 node->tree->node_size, off, len, = new_len); > - > - return new_len; > - } > - > - return len; > -} > - > =C2=A0void hfs_bnode_read(struct hfs_bnode *node, void *buf, u32 off, u32 > len) > =C2=A0{ > =C2=A0 struct page *page; > diff --git a/fs/hfs/btree.c b/fs/hfs/btree.c > index 2eb37a2f64e8..88810b1c90c3 100644 > --- a/fs/hfs/btree.c > +++ b/fs/hfs/btree.c > @@ -15,6 +15,75 @@ > =C2=A0 > =C2=A0#include "btree.h" > =C2=A0 > +/* Context for iterating b-tree map pages > + * @page_idx: The index of the page within the b-node's page array > + * @off: The byte offset within the mapped page > + * @len: The remaining length of the map record > + */ > +struct hfs_bmap_ctx { > + unsigned int page_idx; > + unsigned int off; > + u16 len; > +}; > + > +static struct page *hfs_bmap_get_map_page(struct hfs_bnode *node, > + =C2=A0 struct hfs_bmap_ctx *ctx, > + =C2=A0 u32 byte_offset) We have really nice comments of functions [3,4] for the case of HFS+. I believe it makes to keep the comments for the case of HFS too. Mostly, patch looks good. However, we have one critical issue in the patch. Current code uses hfs_bmap_get_map_page() only in hfs_bmap_test_bit(). But, we have the same logic in hfs_bmap_alloc() [1, 2]. It is not good to have the same logic implemented several times in different places. Also, hfs_bmap_free() could benefit from hfs_bmap_clear_bit() function. Could you please improve your patch? > +{ > + u16 rec_idx, off16; > + unsigned int page_off; > + > + if (node->this =3D=3D HFS_TREE_HEAD) { > + if (node->type !=3D HFS_NODE_HEADER) { > + pr_err("hfs: invalid btree header node\n"); > + return ERR_PTR(-EIO); > + } > + rec_idx =3D HFS_BTREE_HDR_MAP_REC_INDEX; > + } else { > + if (node->type !=3D HFS_NODE_MAP) { > + pr_err("hfs: invalid btree map node\n"); > + return ERR_PTR(-EIO); > + } > + rec_idx =3D HFS_BTREE_MAP_NODE_REC_INDEX; > + } > + > + ctx->len =3D hfs_brec_lenoff(node, rec_idx, &off16); > + if (!ctx->len) > + return ERR_PTR(-ENOENT); > + > + if (!is_bnode_offset_valid(node, off16)) > + return ERR_PTR(-EIO); > + > + ctx->len =3D check_and_correct_requested_length(node, off16, > ctx->len); > + > + if (byte_offset >=3D ctx->len) > + return ERR_PTR(-EINVAL); > + > + page_off =3D (u32)off16 + node->page_offset + byte_offset; > + ctx->page_idx =3D page_off >> PAGE_SHIFT; > + ctx->off =3D page_off & ~PAGE_MASK; > + > + return node->page[ctx->page_idx]; > +} > + > +static bool hfs_bmap_test_bit(struct hfs_bnode *node, u32 > node_bit_idx) > +{ > + struct hfs_bmap_ctx ctx; > + struct page *page; > + u8 *bmap, byte, mask; > + > + page =3D hfs_bmap_get_map_page(node, &ctx, node_bit_idx / > BITS_PER_BYTE); > + if (IS_ERR(page)) > + return false; > + > + bmap =3D kmap_local_page(page); > + byte =3D bmap[ctx.off]; > + kunmap_local(bmap); > + > + mask =3D 1 << (7 - (node_bit_idx % BITS_PER_BYTE)); > + return (byte & mask) !=3D 0; > +} > + > =C2=A0/* Get a reference to a B*Tree and do some initial checks */ > =C2=A0struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id, > btree_keycmp keycmp) > =C2=A0{ > @@ -23,6 +92,7 @@ struct hfs_btree *hfs_btree_open(struct super_block > *sb, u32 id, btree_keycmp ke > =C2=A0 struct address_space *mapping; > =C2=A0 struct folio *folio; > =C2=A0 struct buffer_head *bh; > + struct hfs_bnode *node; > =C2=A0 unsigned int size; > =C2=A0 u16 dblock; > =C2=A0 sector_t start_block; > @@ -155,6 +225,20 @@ struct hfs_btree *hfs_btree_open(struct > super_block *sb, u32 id, btree_keycmp ke > =C2=A0 kunmap_local(head); > =C2=A0 folio_unlock(folio); > =C2=A0 folio_put(folio); > + > + node =3D hfs_bnode_find(tree, HFS_TREE_HEAD); > + if (IS_ERR(node)) > + goto free_inode; > + > + if (!hfs_bmap_test_bit(node, HFS_TREE_HEAD)) { > + pr_warn("(%s): %s (cnid 0x%x) bitmap corrupted, > forcing rdonly\n", > + sb->s_id, id =3D=3D HFS_EXT_CNID ? "extents" : > "catalog", id); > + pr_warn("Run fsck.hfs to repair.\n"); > + sb->s_flags |=3D SB_RDONLY; > + } > + > + hfs_bnode_put(node); > + > =C2=A0 return tree; > =C2=A0 > =C2=A0fail_folio: > diff --git a/fs/hfs/btree.h b/fs/hfs/btree.h > index 99be858b2446..f8afa33f709a 100644 > --- a/fs/hfs/btree.h > +++ b/fs/hfs/btree.h > @@ -129,3 +129,43 @@ extern int __hfs_brec_find(struct hfs_bnode > *bnode, struct hfs_find_data *fd); > =C2=A0extern int hfs_brec_find(struct hfs_find_data *fd); > =C2=A0extern int hfs_brec_read(struct hfs_find_data *fd, void *rec, u32 > rec_len); > =C2=A0extern int hfs_brec_goto(struct hfs_find_data *fd, int cnt); > + > +static inline bool is_bnode_offset_valid(struct hfs_bnode *node, u32 > off) > +{ > + bool is_valid; > + > + if (!node || !node->tree) > + return false; > + > + is_valid =3D off < node->tree->node_size; > + > + if (!is_valid) { > + pr_err("invalid offset: id %u, type %x, h %u, sz %u, > off %u\n", type %#x > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 node->this, node->type, node->hei= ght, > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 node->tree->node_size, off); > + } > + > + return is_valid; > +} > + > +static inline u32 check_and_correct_requested_length(struct > hfs_bnode *node, u32 off, u32 len) > +{ > + unsigned int node_size; > + > + if (!is_bnode_offset_valid(node, off)) > + return 0; > + > + node_size =3D node->tree->node_size; > + > + if ((u64)off + len > node_size) { > + u32 new_len =3D node_size - off; > + > + pr_err("corrected len: id %u, type %x, h %u, sz %u, > off %u, len %u->%u\n", type %#x > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 node->this, node->type, node->hei= ght, > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 node_size, off, len, new_len); > + > + return new_len; > + } > + > + return len; > +} > diff --git a/include/linux/hfs_common.h b/include/linux/hfs_common.h > index 45fb4c9ff9f5..d6a615e74b26 100644 > --- a/include/linux/hfs_common.h > +++ b/include/linux/hfs_common.h > @@ -510,14 +510,21 @@ struct hfs_btree_header_rec { > =C2=A0 =C2=A0=C2=A0 b-tree but not in > extents > =C2=A0 =C2=A0=C2=A0 b-tree (hfsplus). > */ > =C2=A0 > +/* HFS BTree misc info */ > +#define HFS_TREE_HEAD 0 > +#define HFS_BTREE_HDR_MAP_REC_INDEX 2 /* Map > (bitmap) record in Header node */ > +#define HFS_BTREE_MAP_NODE_REC_INDEX 0 /* Map > record in Map Node */ > + > =C2=A0/* HFS+ BTree misc info */ > -#define HFSPLUS_TREE_HEAD 0 > +#define HFSPLUS_TREE_HEAD HFS_TREE_HEAD > =C2=A0#define HFSPLUS_NODE_MXSZ 32768 > =C2=A0#define HFSPLUS_NODE_MINSZ 512 > =C2=A0#define HFSPLUS_ATTR_TREE_NODE_SIZE 8192 > =C2=A0#define HFSPLUS_BTREE_HDR_NODE_RECS_COUNT 3 > -#define HFSPLUS_BTREE_HDR_MAP_REC_INDEX 2 /* > Map (bitmap) record in Header node */ > -#define HFSPLUS_BTREE_MAP_NODE_REC_INDEX 0 /* Map > record in Map Node */ > +/* Map (bitmap) record in Header node */ > +#define > HFSPLUS_BTREE_HDR_MAP_REC_INDEX HFS_BTREE_HDR_MAP_REC_INDEX > +/* Map record in Map Node */ > +#define > HFSPLUS_BTREE_MAP_NODE_REC_INDEX HFS_BTREE_MAP_NODE_REC_INDEX > =C2=A0#define HFSPLUS_BTREE_HDR_USER_BYTES 128 > =C2=A0#define HFSPLUS_BTREE_MAP_NODE_RECS_COUNT 2 > =C2=A0#define HFSPLUS_BTREE_MAP_NODE_RESERVED_BYTES 2 Thanks, Slava. [1] https://elixir.bootlin.com/linux/v7.2-rc3/source/fs/hfs/btree.c#L307 [2] https://elixir.bootlin.com/linux/v7.2-rc3/source/fs/hfs/btree.c#L352 [3] https://elixir.bootlin.com/linux/v7.2-rc3/source/fs/hfsplus/btree.c#L144 [4] https://elixir.bootlin.com/linux/v7.2-rc3/source/fs/hfsplus/btree.c#L190