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Commit 011fa994 authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

ext4: prevent online resize with backup superblock 



Prevent BUG or corrupted file systems after the following:

mkfs.ext4 /dev/vdc 100M
mount -t ext4 -o sb=40961 /dev/vdc /vdc
resize2fs /dev/vdc

We previously prevented online resizing using the old resize ioctl.
Move the code to ext4_resize_begin(), so the check applies for all of
the resize ioctl's.

Reported-by: default avatarMaxim Malkov <malkov@ispras.ru>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 50db71ab

fs/ext4/resize.c

+12 −12
Original line number Diff line number Diff line
@@ -23,6 +23,18 @@ int ext4_resize_begin(struct super_block *sb) 
	if (!capable(CAP_SYS_RESOURCE))

		return -EPERM;



	/*

	 * If we are not using the primary superblock/GDT copy don't resize,

         * because the user tools have no way of handling this.  Probably a

         * bad time to do it anyways.

         */

	if (EXT4_SB(sb)->s_sbh->b_blocknr !=

	    le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block)) {

		ext4_warning(sb, "won't resize using backup superblock at %llu",

			(unsigned long long)EXT4_SB(sb)->s_sbh->b_blocknr);

		return -EPERM;

	}



	/*

	 * We are not allowed to do online-resizing on a filesystem mounted

	 * with error, because it can destroy the filesystem easily.
@@ -758,18 +770,6 @@ static int add_new_gdb(handle_t *handle, struct inode *inode, 
		       "EXT4-fs: ext4_add_new_gdb: adding group block %lu\n",

		       gdb_num);



	/*

	 * If we are not using the primary superblock/GDT copy don't resize,

         * because the user tools have no way of handling this.  Probably a

         * bad time to do it anyways.

         */

	if (EXT4_SB(sb)->s_sbh->b_blocknr !=

	    le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block)) {

		ext4_warning(sb, "won't resize using backup superblock at %llu",

			(unsigned long long)EXT4_SB(sb)->s_sbh->b_blocknr);

		return -EPERM;

	}



	gdb_bh = sb_bread(sb, gdblock);

	if (!gdb_bh)

		return -EIO;