Commit 005d4b0d authored by Tetsuo Handa's avatar Tetsuo Handa Committed by Viacheslav Dubeyko
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hfsplus: Verify inode mode when loading from disk 



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: default avatarsyzbot <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: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: default avatarViacheslav Dubeyko <slava@dubeyko.com>
Signed-off-by: default avatarViacheslav Dubeyko <slava@dubeyko.com>
Link: https://lore.kernel.org/r/04ded9f9-73fb-496c-bfa5-89c4f5d1d7bb@I-love.SAKURA.ne.jp


Signed-off-by: default avatarViacheslav Dubeyko <slava@dubeyko.com>
parent ed490f36

fs/hfsplus/inode.c

+28 −4
Original line number Diff line number Diff line
@@ -180,13 +180,29 @@ const struct dentry_operations hfsplus_dentry_operations = { 
	.d_compare    = hfsplus_compare_dentry,

};



static void hfsplus_get_perms(struct inode *inode,

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)