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ext4: WARN if a full dir leaf block has only one dentry

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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: Theodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20240823160518.GA424729@mit.edu
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20241008121152.3771906-1-libaokun@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Baokun Li 2024-10-08 20:11:52 +08:00 committed by Theodore Ts'o
parent fdfa648ab9
commit 40eb3104cf
1 changed files with 12 additions and 2 deletions
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14
fs/ext4/namei.c
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@ -2000,8 +2000,17 @@ static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir,
else else
split = count/2; 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; 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", dxtrace(printk(KERN_INFO "Split block %lu at %x, %i/%i\n",
(unsigned long)dx_get_block(frame->at), (unsigned long)dx_get_block(frame->at),
hash2, split, count-split)); hash2, split, count-split));
@ -2043,10 +2052,11 @@ static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir,
return de; return de;
journal_error: journal_error:
ext4_std_error(dir->i_sb, err);
out:
brelse(*bh); brelse(*bh);
brelse(bh2); brelse(bh2);
*bh = NULL; *bh = NULL;
ext4_std_error(dir->i_sb, err);
return ERR_PTR(err); return ERR_PTR(err);
} }