Commit 40eb3104 authored by Baokun Li's avatar Baokun Li Committed by Theodore Ts'o
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ext4: WARN if a full dir leaf block has only one dentry 



The maximum length of a filename is 255 and the minimum block size is 1024,
so it is always guaranteed that the number of entries is greater than or
equal to 2 when do_split() is called. So unless ext4_dx_add_entry() and
make_indexed_dir() or some other functions are buggy, 'split == 0' will
not occur.

Setting 'continued' to 0 in this case masks the problem that the file
system has become corrupted, even though it prevents possible out-of-bounds
access. Hence WARN_ON_ONCE() is used to check if 'split' is 0, and if it is
then warns and returns an error to abort split.

Suggested-by: default avatarTheodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20240823160518.GA424729@mit.edu


Signed-off-by: default avatarBaokun Li <libaokun1@huawei.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20241008121152.3771906-1-libaokun@huaweicloud.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent fdfa648a

fs/ext4/namei.c

+12 −2
Original line number Diff line number Diff line
@@ -2000,8 +2000,17 @@ static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir, 
	else

		split = count/2;



	if (WARN_ON_ONCE(split == 0)) {

		/* Should never happen, but avoid out-of-bounds access below */

		ext4_error_inode_block(dir, (*bh)->b_blocknr, 0,

			"bad indexed directory? hash=%08x:%08x count=%d move=%u",

			hinfo->hash, hinfo->minor_hash, count, move);

		err = -EFSCORRUPTED;

		goto out;

	}



	hash2 = map[split].hash;

	continued = split > 0 ? hash2 == map[split - 1].hash : 0;

	continued = hash2 == map[split - 1].hash;

	dxtrace(printk(KERN_INFO "Split block %lu at %x, %i/%i\n",

			(unsigned long)dx_get_block(frame->at),

					hash2, split, count-split));
@@ -2043,10 +2052,11 @@ static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir, 
	return de;



journal_error:

	ext4_std_error(dir->i_sb, err);

out:

	brelse(*bh);

	brelse(bh2);

	*bh = NULL;

	ext4_std_error(dir->i_sb, err);

	return ERR_PTR(err);

}