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Message-ID: <20251103131023.2804655-1-jkoolstra@xs4all.nl>
Date: Mon, 3 Nov 2025 14:10:10 +0100
From: Jori Koolstra <jkoolstra@...all.nl>
To: Viacheslav Dubeyko <slava@...eyko.com>,
John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
Yangtao Li <frank.li@...o.com>
Cc: jkoolstra@...all.nl,
linux-kernel@...r.kernel.org,
linux-fsdevel@...r.kernel.org,
syzbot+17cc9bb6d8d69b4139f0@...kaller.appspotmail.com
Subject: [PATCH] Replace BUG_ON with error handling in hfs_new_inode()
In a06ec283e125 next_id, folder_count, and file_count in the super block
info were expanded to 64 bits, and BUG_ONs were added to detect
overflow. This triggered an error reported by syzbot: if the MDB is
corrupted, the BUG_ON is triggered. This patch replaces this mechanism
with proper error handling and resolves the syzbot reported bug.
hfs_new_inode() is the only place were the 32-bit limits need to be
verified, since only in that function can these values be increased.
Therefore, the checks in hfs_mdb_commit() and hfs_delete_inode() are
removed.
Singed-off-by: Jori Koolstra <jkoolstra@...all.nl>
Reported-by: syzbot+17cc9bb6d8d69b4139f0@...kaller.appspotmail.com
Closes: https://syzbot.org/bug?extid=17cc9bb6d8d69b4139f0
Signed-off-by: Jori Koolstra <jkoolstra@...all.nl>
---
fs/hfs/dir.c | 8 ++++----
fs/hfs/inode.c | 30 ++++++++++++++++++++++++------
fs/hfs/mdb.c | 3 ---
3 files changed, 28 insertions(+), 13 deletions(-)
diff --git a/fs/hfs/dir.c b/fs/hfs/dir.c
index 86a6b317b474..ee1760305380 100644
--- a/fs/hfs/dir.c
+++ b/fs/hfs/dir.c
@@ -196,8 +196,8 @@ static int hfs_create(struct mnt_idmap *idmap, struct inode *dir,
int res;
inode = hfs_new_inode(dir, &dentry->d_name, mode);
- if (!inode)
- return -ENOMEM;
+ if (IS_ERR(inode))
+ return PTR_ERR(inode);
res = hfs_cat_create(inode->i_ino, dir, &dentry->d_name, inode);
if (res) {
@@ -226,8 +226,8 @@ static struct dentry *hfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
int res;
inode = hfs_new_inode(dir, &dentry->d_name, S_IFDIR | mode);
- if (!inode)
- return ERR_PTR(-ENOMEM);
+ if (IS_ERR(inode))
+ return ERR_CAST(inode);
res = hfs_cat_create(inode->i_ino, dir, &dentry->d_name, inode);
if (res) {
diff --git a/fs/hfs/inode.c b/fs/hfs/inode.c
index 9cd449913dc8..beec6fe7e801 100644
--- a/fs/hfs/inode.c
+++ b/fs/hfs/inode.c
@@ -186,16 +186,23 @@ struct inode *hfs_new_inode(struct inode *dir, const struct qstr *name, umode_t
s64 next_id;
s64 file_count;
s64 folder_count;
+ int err = -ENOMEM;
if (!inode)
- return NULL;
+ goto out_err;
+
+ err = -ENOSPC;
mutex_init(&HFS_I(inode)->extents_lock);
INIT_LIST_HEAD(&HFS_I(inode)->open_dir_list);
spin_lock_init(&HFS_I(inode)->open_dir_lock);
hfs_cat_build_key(sb, (btree_key *)&HFS_I(inode)->cat_key, dir->i_ino, name);
next_id = atomic64_inc_return(&HFS_SB(sb)->next_id);
- BUG_ON(next_id > U32_MAX);
+ if (next_id > U32_MAX) {
+ pr_err("hfs: next file ID exceeds 32-bit limit — possible "
+ "superblock corruption");
+ goto out_discard;
+ }
inode->i_ino = (u32)next_id;
inode->i_mode = mode;
inode->i_uid = current_fsuid();
@@ -209,7 +216,11 @@ struct inode *hfs_new_inode(struct inode *dir, const struct qstr *name, umode_t
if (S_ISDIR(mode)) {
inode->i_size = 2;
folder_count = atomic64_inc_return(&HFS_SB(sb)->folder_count);
- BUG_ON(folder_count > U32_MAX);
+ if (folder_count > U32_MAX) {
+ pr_err("hfs: folder count exceeds 32-bit limit — possible "
+ "superblock corruption");
+ goto out_discard;
+ }
if (dir->i_ino == HFS_ROOT_CNID)
HFS_SB(sb)->root_dirs++;
inode->i_op = &hfs_dir_inode_operations;
@@ -219,7 +230,11 @@ struct inode *hfs_new_inode(struct inode *dir, const struct qstr *name, umode_t
} else if (S_ISREG(mode)) {
HFS_I(inode)->clump_blocks = HFS_SB(sb)->clumpablks;
file_count = atomic64_inc_return(&HFS_SB(sb)->file_count);
- BUG_ON(file_count > U32_MAX);
+ if (file_count > U32_MAX) {
+ pr_err("hfs: file count exceeds 32-bit limit — possible "
+ "superblock corruption");
+ goto out_discard;
+ }
if (dir->i_ino == HFS_ROOT_CNID)
HFS_SB(sb)->root_files++;
inode->i_op = &hfs_file_inode_operations;
@@ -243,6 +258,11 @@ struct inode *hfs_new_inode(struct inode *dir, const struct qstr *name, umode_t
hfs_mark_mdb_dirty(sb);
return inode;
+
+ out_discard:
+ iput(inode);
+ out_err:
+ return ERR_PTR(err);
}
void hfs_delete_inode(struct inode *inode)
@@ -251,7 +271,6 @@ void hfs_delete_inode(struct inode *inode)
hfs_dbg("ino %lu\n", inode->i_ino);
if (S_ISDIR(inode->i_mode)) {
- BUG_ON(atomic64_read(&HFS_SB(sb)->folder_count) > U32_MAX);
atomic64_dec(&HFS_SB(sb)->folder_count);
if (HFS_I(inode)->cat_key.ParID == cpu_to_be32(HFS_ROOT_CNID))
HFS_SB(sb)->root_dirs--;
@@ -260,7 +279,6 @@ void hfs_delete_inode(struct inode *inode)
return;
}
- BUG_ON(atomic64_read(&HFS_SB(sb)->file_count) > U32_MAX);
atomic64_dec(&HFS_SB(sb)->file_count);
if (HFS_I(inode)->cat_key.ParID == cpu_to_be32(HFS_ROOT_CNID))
HFS_SB(sb)->root_files--;
diff --git a/fs/hfs/mdb.c b/fs/hfs/mdb.c
index 53f3fae60217..1c3fb631cc8e 100644
--- a/fs/hfs/mdb.c
+++ b/fs/hfs/mdb.c
@@ -273,15 +273,12 @@ void hfs_mdb_commit(struct super_block *sb)
/* These parameters may have been modified, so write them back */
mdb->drLsMod = hfs_mtime();
mdb->drFreeBks = cpu_to_be16(HFS_SB(sb)->free_ablocks);
- BUG_ON(atomic64_read(&HFS_SB(sb)->next_id) > U32_MAX);
mdb->drNxtCNID =
cpu_to_be32((u32)atomic64_read(&HFS_SB(sb)->next_id));
mdb->drNmFls = cpu_to_be16(HFS_SB(sb)->root_files);
mdb->drNmRtDirs = cpu_to_be16(HFS_SB(sb)->root_dirs);
- BUG_ON(atomic64_read(&HFS_SB(sb)->file_count) > U32_MAX);
mdb->drFilCnt =
cpu_to_be32((u32)atomic64_read(&HFS_SB(sb)->file_count));
- BUG_ON(atomic64_read(&HFS_SB(sb)->folder_count) > U32_MAX);
mdb->drDirCnt =
cpu_to_be32((u32)atomic64_read(&HFS_SB(sb)->folder_count));
--
2.51.1.dirty
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