Commit aba16408 authored Sep 21, 2022 by Zhihao Cheng Committed by Zheng Zengkai Sep 21, 2022

quota: Check next/prev free block number after reading from quota file

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5QH0X
CVE: NA

--------------------------------

Following process:
 Init: v2_read_file_info: <3> dqi_free_blk 0 dqi_free_entry 5 dqi_blks 6

 Step 1. chown bin f_a -> dquot_acquire -> v2_write_dquot:
  qtree_write_dquot
   do_insert_tree
    find_free_dqentry
     get_free_dqblk
      write_blk(info->dqi_blocks) // info->dqi_blocks = 6, failure. The
	   content in physical block (corresponding to blk 6) is random.

 Step 2. chown root f_a -> dquot_transfer -> dqput_all -> dqput ->
         ext4_release_dquot -> v2_release_dquot -> qtree_delete_dquot:
  dquot_release
   remove_tree
    free_dqentry
     put_free_dqblk(6)
      info->dqi_free_blk = blk    // info->dqi_free_blk = 6

 Step 3. drop cache (buffer head for block 6 is released)

 Step 4. chown bin f_b -> dquot_acquire -> commit_dqblk -> v2_write_dquot:
  qtree_write_dquot
   do_insert_tree
    find_free_dqentry
     get_free_dqblk
      dh = (struct qt_disk_dqdbheader *)buf
      blk = info->dqi_free_blk     // 6
      ret = read_blk(info, blk, buf)  // The content of buf is random
      info->dqi_free_blk = le32_to_cpu(dh->dqdh_next_free)  // random blk

 Step 5. chown bin f_c -> notify_change -> ext4_setattr -> dquot_transfer:
  dquot = dqget -> acquire_dquot -> ext4_acquire_dquot -> dquot_acquire ->
          commit_dqblk -> v2_write_dquot -> dq_insert_tree:
   do_insert_tree
    find_free_dqentry
     get_free_dqblk
      blk = info->dqi_free_blk    // If blk < 0 and blk is not an error
				     code, it will be returned as dquot

  transfer_to[USRQUOTA] = dquot  // A random negative value
  __dquot_transfer(transfer_to)
   dquot_add_inodes(transfer_to[cnt])
    spin_lock(&dquot->dq_dqb_lock)  // page fault

, which will lead to kernel page fault:
 Quota error (device sda): qtree_write_dquot: Error -8000 occurred
 while creating quota
 BUG: unable to handle page fault for address: ffffffffffffe120
 #PF: supervisor write access in kernel mode
 #PF: error_code(0x0002) - not-present page
 Oops: 0002 [#1] PREEMPT SMP
 CPU: 0 PID: 5974 Comm: chown Not tainted 6.0.0-rc1-00004
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
 RIP: 0010:_raw_spin_lock+0x3a/0x90
 Call Trace:
  dquot_add_inodes+0x28/0x270
  __dquot_transfer+0x377/0x840
  dquot_transfer+0xde/0x540
  ext4_setattr+0x405/0x14d0
  notify_change+0x68e/0x9f0
  chown_common+0x300/0x430
  __x64_sys_fchownat+0x29/0x40

In order to avoid accessing invalid quota memory address, this patch adds
block number checking of next/prev free block read from quota file.

Fetch a reproducer in [Link].

Link: https://bugzilla.kernel.org/show_bug.cgi?id=216372


Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>

parent e89e2d3b

fs/quota/quota_tree.c

+38 −0

Original line number	Diff line number	Diff line
		@@ -80,6 +80,35 @@ static ssize_t write_blk(struct qtree_mem_dqinfo info, uint blk, char buf)
		return ret;
		}

		static inline int do_check_range(struct super_block *sb, uint val, uint max_val)
		{
		if (val >= max_val) {
		quota_error(sb, "Getting block too big (%u >= %u)",
		val, max_val);
		return -EUCLEAN;
		}

		return 0;
		}

		static int check_free_block(struct qtree_mem_dqinfo *info,
		struct qt_disk_dqdbheader *dh)
		{
		int err = 0;
		uint nextblk, prevblk;

		nextblk = le32_to_cpu(dh->dqdh_next_free);
		err = do_check_range(info->dqi_sb, nextblk, info->dqi_blocks);
		if (err)
		return err;
		prevblk = le32_to_cpu(dh->dqdh_prev_free);
		err = do_check_range(info->dqi_sb, prevblk, info->dqi_blocks);
		if (err)
		return err;

		return err;
		}

		/* Remove empty block from list and return it */
		static int get_free_dqblk(struct qtree_mem_dqinfo *info)
		{
		@@ -94,6 +123,9 @@ static int get_free_dqblk(struct qtree_mem_dqinfo *info)
		ret = read_blk(info, blk, buf);
		if (ret < 0)
		goto out_buf;
		ret = check_free_block(info, dh);
		if (ret)
		goto out_buf;
		info->dqi_free_blk = le32_to_cpu(dh->dqdh_next_free);
		}
		else {
		@@ -241,6 +273,9 @@ static uint find_free_dqentry(struct qtree_mem_dqinfo *info,
		*err = read_blk(info, blk, buf);
		if (*err < 0)
		goto out_buf;
		*err = check_free_block(info, dh);
		if (*err)
		goto out_buf;
		} else {
		blk = get_free_dqblk(info);
		if ((int)blk < 0) {
		@@ -433,6 +468,9 @@ static int free_dqentry(struct qtree_mem_dqinfo info, struct dquot dquot,
		goto out_buf;
		}
		dh = (struct qt_disk_dqdbheader *)buf;
		ret = check_free_block(info, dh);
		if (ret)
		goto out_buf;
		le16_add_cpu(&dh->dqdh_entries, -1);
		if (!le16_to_cpu(dh->dqdh_entries)) { /* Block got free? */
		ret = remove_free_dqentry(info, buf, blk);