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hfsplus: Verify inode mode when loading from disk

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syzbot is reporting that S_IFMT bits of inode->i_mode can become bogus when
the S_IFMT bits of the 16bits "mode" field loaded from disk are corrupted.

According to [1], the permissions field was treated as reserved in Mac OS
8 and 9. According to [2], the reserved field was explicitly initialized
with 0, and that field must remain 0 as long as reserved. Therefore, when
the "mode" field is not 0 (i.e. no longer reserved), the file must be
S_IFDIR if dir == 1, and the file must be one of S_IFREG/S_IFLNK/S_IFCHR/
S_IFBLK/S_IFIFO/S_IFSOCK if dir == 0.

Reported-by: syzbot <syzbot+895c23f6917da440ed0d@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=895c23f6917da440ed0d
Link: https://developer.apple.com/library/archive/technotes/tn/tn1150.html#HFSPlusPermissions [1]
Link: https://developer.apple.com/library/archive/technotes/tn/tn1150.html#ReservedAndPadFields [2]
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Viacheslav Dubeyko <slava@dubeyko.com>
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>
Link: https://lore.kernel.org/r/04ded9f9-73fb-496c-bfa5-89c4f5d1d7bb@I-love.SAKURA.ne.jp
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>
This commit is contained in:
Tetsuo Handa 2025-11-15 18:18:54 +09:00 • committed by Viacheslav Dubeyko
parent ed490f36f4
commit 005d4b0d33
1 changed files with 28 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

32
fs/hfsplus/inode.c
View file

@ -180,13 +180,29 @@ const struct dentry_operations hfsplus_dentry_operations = {
.d_compare = hfsplus_compare_dentry,
};
static void hfsplus_get_perms(struct inode *inode,
struct hfsplus_perm *perms, int dir)
static int hfsplus_get_perms(struct inode *inode,
struct hfsplus_perm *perms, int dir)
{
struct hfsplus_sb_info *sbi = HFSPLUS_SB(inode->i_sb);
u16 mode;
mode = be16_to_cpu(perms->mode);
if (dir) {
if (mode && !S_ISDIR(mode))
goto bad_type;
} else if (mode) {
switch (mode & S_IFMT) {
case S_IFREG:
case S_IFLNK:
case S_IFCHR:
case S_IFBLK:
case S_IFIFO:
case S_IFSOCK:
break;
default:
goto bad_type;
}
}
i_uid_write(inode, be32_to_cpu(perms->owner));
if ((test_bit(HFSPLUS_SB_UID, &sbi->flags)) || (!i_uid_read(inode) && !mode))
@ -212,6 +228,10 @@ static void hfsplus_get_perms(struct inode *inode,
inode->i_flags |= S_APPEND;
else
inode->i_flags &= ~S_APPEND;
return 0;
bad_type:
pr_err("invalid file type 0%04o for inode %lu\n", mode, inode->i_ino);
return -EIO;
}
static int hfsplus_file_open(struct inode *inode, struct file *file)
@ -516,7 +536,9 @@ int hfsplus_cat_read_inode(struct inode *inode, struct hfs_find_data *fd)
}
hfs_bnode_read(fd->bnode, &entry, fd->entryoffset,
sizeof(struct hfsplus_cat_folder));
hfsplus_get_perms(inode, &folder->permissions, 1);
res = hfsplus_get_perms(inode, &folder->permissions, 1);
if (res)
goto out;
set_nlink(inode, 1);
inode->i_size = 2 + be32_to_cpu(folder->valence);
inode_set_atime_to_ts(inode, hfsp_mt2ut(folder->access_date));
@ -545,7 +567,9 @@ int hfsplus_cat_read_inode(struct inode *inode, struct hfs_find_data *fd)
hfsplus_inode_read_fork(inode, HFSPLUS_IS_RSRC(inode) ?
&file->rsrc_fork : &file->data_fork);
hfsplus_get_perms(inode, &file->permissions, 0);
res = hfsplus_get_perms(inode, &file->permissions, 0);
if (res)
goto out;
set_nlink(inode, 1);
if (S_ISREG(inode->i_mode)) {
if (file->permissions.dev)