Commit 9803387c authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

ext4: validate the debug_want_extra_isize mount option at parse time 

Instead of setting s_want_extra_size and then making sure that it is a
valid value afterwards, validate the field before we set it.  This
avoids races and other problems when remounting the file system.

Link: https://lore.kernel.org/r/20191215063020.GA11512@mit.edu


Cc: stable@kernel.org
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Reported-and-tested-by: default avatar <syzbot+4a39a025912b265cacef@syzkaller.appspotmail.com>
parent a70fd5ac

fs/ext4/super.c

+69 −74
Original line number Diff line number Diff line
@@ -1886,6 +1886,13 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token, 
		}

		sbi->s_commit_interval = HZ * arg;

	} else if (token == Opt_debug_want_extra_isize) {

		if ((arg & 1) ||

		    (arg < 4) ||

		    (arg > (sbi->s_inode_size - EXT4_GOOD_OLD_INODE_SIZE))) {

			ext4_msg(sb, KERN_ERR,

				 "Invalid want_extra_isize %d", arg);

			return -1;

		}

		sbi->s_want_extra_isize = arg;

	} else if (token == Opt_max_batch_time) {

		sbi->s_max_batch_time = arg;
@@ -3540,40 +3547,6 @@ int ext4_calculate_overhead(struct super_block *sb) 
	return 0;

}



static void ext4_clamp_want_extra_isize(struct super_block *sb)

{

	struct ext4_sb_info *sbi = EXT4_SB(sb);

	struct ext4_super_block *es = sbi->s_es;

	unsigned def_extra_isize = sizeof(struct ext4_inode) -

						EXT4_GOOD_OLD_INODE_SIZE;



	if (sbi->s_inode_size == EXT4_GOOD_OLD_INODE_SIZE) {

		sbi->s_want_extra_isize = 0;

		return;

	}

	if (sbi->s_want_extra_isize < 4) {

		sbi->s_want_extra_isize = def_extra_isize;

		if (ext4_has_feature_extra_isize(sb)) {

			if (sbi->s_want_extra_isize <

			    le16_to_cpu(es->s_want_extra_isize))

				sbi->s_want_extra_isize =

					le16_to_cpu(es->s_want_extra_isize);

			if (sbi->s_want_extra_isize <

			    le16_to_cpu(es->s_min_extra_isize))

				sbi->s_want_extra_isize =

					le16_to_cpu(es->s_min_extra_isize);

		}

	}

	/* Check if enough inode space is available */

	if ((sbi->s_want_extra_isize > sbi->s_inode_size) ||

	    (EXT4_GOOD_OLD_INODE_SIZE + sbi->s_want_extra_isize >

							sbi->s_inode_size)) {

		sbi->s_want_extra_isize = def_extra_isize;

		ext4_msg(sb, KERN_INFO,

			 "required extra inode space not available");

	}

}



static void ext4_set_resv_clusters(struct super_block *sb)

{

	ext4_fsblk_t resv_clusters;
@@ -3781,6 +3754,68 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) 
	 */

	sbi->s_li_wait_mult = EXT4_DEF_LI_WAIT_MULT;



	if (le32_to_cpu(es->s_rev_level) == EXT4_GOOD_OLD_REV) {

		sbi->s_inode_size = EXT4_GOOD_OLD_INODE_SIZE;

		sbi->s_first_ino = EXT4_GOOD_OLD_FIRST_INO;

	} else {

		sbi->s_inode_size = le16_to_cpu(es->s_inode_size);

		sbi->s_first_ino = le32_to_cpu(es->s_first_ino);

		if (sbi->s_first_ino < EXT4_GOOD_OLD_FIRST_INO) {

			ext4_msg(sb, KERN_ERR, "invalid first ino: %u",

				 sbi->s_first_ino);

			goto failed_mount;

		}

		if ((sbi->s_inode_size < EXT4_GOOD_OLD_INODE_SIZE) ||

		    (!is_power_of_2(sbi->s_inode_size)) ||

		    (sbi->s_inode_size > blocksize)) {

			ext4_msg(sb, KERN_ERR,

			       "unsupported inode size: %d",

			       sbi->s_inode_size);

			goto failed_mount;

		}

		/*

		 * i_atime_extra is the last extra field available for

		 * [acm]times in struct ext4_inode. Checking for that

		 * field should suffice to ensure we have extra space

		 * for all three.

		 */

		if (sbi->s_inode_size >= offsetof(struct ext4_inode, i_atime_extra) +

			sizeof(((struct ext4_inode *)0)->i_atime_extra)) {

			sb->s_time_gran = 1;

			sb->s_time_max = EXT4_EXTRA_TIMESTAMP_MAX;

		} else {

			sb->s_time_gran = NSEC_PER_SEC;

			sb->s_time_max = EXT4_NON_EXTRA_TIMESTAMP_MAX;

		}

		sb->s_time_min = EXT4_TIMESTAMP_MIN;

	}

	if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE) {

		sbi->s_want_extra_isize = sizeof(struct ext4_inode) -

			EXT4_GOOD_OLD_INODE_SIZE;

		if (ext4_has_feature_extra_isize(sb)) {

			unsigned v, max = (sbi->s_inode_size -

					   EXT4_GOOD_OLD_INODE_SIZE);



			v = le16_to_cpu(es->s_want_extra_isize);

			if (v > max) {

				ext4_msg(sb, KERN_ERR,

					 "bad s_want_extra_isize: %d", v);

				goto failed_mount;

			}

			if (sbi->s_want_extra_isize < v)

				sbi->s_want_extra_isize = v;



			v = le16_to_cpu(es->s_min_extra_isize);

			if (v > max) {

				ext4_msg(sb, KERN_ERR,

					 "bad s_min_extra_isize: %d", v);

				goto failed_mount;

			}

			if (sbi->s_want_extra_isize < v)

				sbi->s_want_extra_isize = v;

		}

	}



	if (sbi->s_es->s_mount_opts[0]) {

		char *s_mount_opts = kstrndup(sbi->s_es->s_mount_opts,

					      sizeof(sbi->s_es->s_mount_opts),
@@ -4019,42 +4054,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) 
						      has_huge_files);

	sb->s_maxbytes = ext4_max_size(sb->s_blocksize_bits, has_huge_files);



	if (le32_to_cpu(es->s_rev_level) == EXT4_GOOD_OLD_REV) {

		sbi->s_inode_size = EXT4_GOOD_OLD_INODE_SIZE;

		sbi->s_first_ino = EXT4_GOOD_OLD_FIRST_INO;

	} else {

		sbi->s_inode_size = le16_to_cpu(es->s_inode_size);

		sbi->s_first_ino = le32_to_cpu(es->s_first_ino);

		if (sbi->s_first_ino < EXT4_GOOD_OLD_FIRST_INO) {

			ext4_msg(sb, KERN_ERR, "invalid first ino: %u",

				 sbi->s_first_ino);

			goto failed_mount;

		}

		if ((sbi->s_inode_size < EXT4_GOOD_OLD_INODE_SIZE) ||

		    (!is_power_of_2(sbi->s_inode_size)) ||

		    (sbi->s_inode_size > blocksize)) {

			ext4_msg(sb, KERN_ERR,

			       "unsupported inode size: %d",

			       sbi->s_inode_size);

			goto failed_mount;

		}

		/*

		 * i_atime_extra is the last extra field available for [acm]times in

		 * struct ext4_inode. Checking for that field should suffice to ensure

		 * we have extra space for all three.

		 */

		if (sbi->s_inode_size >= offsetof(struct ext4_inode, i_atime_extra) +

			sizeof(((struct ext4_inode *)0)->i_atime_extra)) {

			sb->s_time_gran = 1;

			sb->s_time_max = EXT4_EXTRA_TIMESTAMP_MAX;

		} else {

			sb->s_time_gran = NSEC_PER_SEC;

			sb->s_time_max = EXT4_NON_EXTRA_TIMESTAMP_MAX;

		}



		sb->s_time_min = EXT4_TIMESTAMP_MIN;

	}



	sbi->s_desc_size = le16_to_cpu(es->s_desc_size);

	if (ext4_has_feature_64bit(sb)) {

		if (sbi->s_desc_size < EXT4_MIN_DESC_SIZE_64BIT ||
@@ -4503,8 +4502,6 @@ no_journal: 
	} else if (ret)

		goto failed_mount4a;



	ext4_clamp_want_extra_isize(sb);



	ext4_set_resv_clusters(sb);



	err = ext4_setup_system_zone(sb);
@@ -5292,8 +5289,6 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data) 
		goto restore_opts;

	}



	ext4_clamp_want_extra_isize(sb);



	if ((old_opts.s_mount_opt & EXT4_MOUNT_JOURNAL_CHECKSUM) ^

	    test_opt(sb, JOURNAL_CHECKSUM)) {

		ext4_msg(sb, KERN_ERR, "changing journal_checksum "

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