Unverified Commit 8c97a6dd authored by Jori Koolstra's avatar Jori Koolstra Committed by Christian Brauner
Browse files

minix: Add required sanity checking to minix_check_superblock() 



The fs/minix implementation of the minix filesystem does not currently
support any other value for s_log_zone_size than 0. This is also the
only value supported in util-linux; see mkfs.minix.c line 511. In
addition, this patch adds some sanity checking for the other minix
superblock fields, and moves the minix_blocks_needed() checks for the
zmap and imap also to minix_check_super_block().

This also closes a related syzbot bug report.

Signed-off-by: default avatarJori Koolstra <jkoolstra@xs4all.nl>
Link: https://patch.msgid.link/20251208153947.108343-1-jkoolstra@xs4all.nl


Reviewed-by: default avatarJan Kara <jack@suse.cz>
Reported-by: default avatar <syzbot+5ad0824204c7bf9b67f2@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=5ad0824204c7bf9b67f2


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 8f0b4cce

fs/minix/inode.c

+29 −21
Original line number Diff line number Diff line
@@ -170,9 +170,37 @@ static int minix_reconfigure(struct fs_context *fc) 
static bool minix_check_superblock(struct super_block *sb)

{

	struct minix_sb_info *sbi = minix_sb(sb);

	unsigned long block;



	if (sbi->s_imap_blocks == 0 || sbi->s_zmap_blocks == 0)

	if (sbi->s_log_zone_size != 0) {

		printk("minix-fs error: zone size must equal block size. "

		       "s_log_zone_size > 0 is not supported.\n");

		return false;

	}



	if (sbi->s_ninodes < 1 || sbi->s_firstdatazone <= 4 ||

	    sbi->s_firstdatazone >= sbi->s_nzones)

		return false;



	/* Apparently minix can create filesystems that allocate more blocks for

	 * the bitmaps than needed.  We simply ignore that, but verify it didn't

	 * create one with not enough blocks and bail out if so.

	 */

	block = minix_blocks_needed(sbi->s_ninodes, sb->s_blocksize);

	if (sbi->s_imap_blocks < block) {

		printk("MINIX-fs: file system does not have enough "

		       "imap blocks allocated. Refusing to mount.\n");

		return false;

	}



	block = minix_blocks_needed(

			(sbi->s_nzones - sbi->s_firstdatazone + 1),

			sb->s_blocksize);

	if (sbi->s_zmap_blocks < block) {

		printk("MINIX-fs: file system does not have enough "

		       "zmap blocks allocated. Refusing to mount.\n");

		return false;

	}



	/*

	 * s_max_size must not exceed the block mapping limitation.  This check
@@ -293,26 +321,6 @@ static int minix_fill_super(struct super_block *s, struct fs_context *fc) 
	minix_set_bit(0,sbi->s_imap[0]->b_data);

	minix_set_bit(0,sbi->s_zmap[0]->b_data);



	/* Apparently minix can create filesystems that allocate more blocks for

	 * the bitmaps than needed.  We simply ignore that, but verify it didn't

	 * create one with not enough blocks and bail out if so.

	 */

	block = minix_blocks_needed(sbi->s_ninodes, s->s_blocksize);

	if (sbi->s_imap_blocks < block) {

		printk("MINIX-fs: file system does not have enough "

				"imap blocks allocated.  Refusing to mount.\n");

		goto out_no_bitmap;

	}



	block = minix_blocks_needed(

			(sbi->s_nzones - sbi->s_firstdatazone + 1),

			s->s_blocksize);

	if (sbi->s_zmap_blocks < block) {

		printk("MINIX-fs: file system does not have enough "

				"zmap blocks allocated.  Refusing to mount.\n");

		goto out_no_bitmap;

	}



	/* set up enough so that it can read an inode */

	s->s_op = &minix_sops;

	s->s_time_min = 0;