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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Chao Yu <yuchao0@huawei.com>,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        Ben Hutchings <ben.hutchings@codethink.co.uk>
Subject: [PATCH 4.19 09/84] f2fs: check memory boundary by insane namelen
Date:   Fri, 17 Jan 2020 00:17:43 +0100
Message-Id: <20200116231714.655118606@linuxfoundation.org>
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From: Jaegeuk Kim <jaegeuk@kernel.org>

commit 4e240d1bab1ead280ddf5eb05058dba6bbd57d10 upstream.

If namelen is corrupted to have very long value, fill_dentries can copy
wrong memory area.

Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/f2fs/dir.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -806,6 +806,17 @@ int f2fs_fill_dentries(struct dir_contex
 		de_name.name = d->filename[bit_pos];
 		de_name.len = le16_to_cpu(de->name_len);
 
+		/* check memory boundary before moving forward */
+		bit_pos += GET_DENTRY_SLOTS(le16_to_cpu(de->name_len));
+		if (unlikely(bit_pos > d->max)) {
+			f2fs_msg(sbi->sb, KERN_WARNING,
+				"%s: corrupted namelen=%d, run fsck to fix.",
+				__func__, le16_to_cpu(de->name_len));
+			set_sbi_flag(sbi, SBI_NEED_FSCK);
+			err = -EINVAL;
+			goto out;
+		}
+
 		if (f2fs_encrypted_inode(d->inode)) {
 			int save_len = fstr->len;
 
@@ -826,7 +837,6 @@ int f2fs_fill_dentries(struct dir_contex
 		if (sbi->readdir_ra == 1)
 			f2fs_ra_node_page(sbi, le32_to_cpu(de->ino));
 
-		bit_pos += GET_DENTRY_SLOTS(le16_to_cpu(de->name_len));
 		ctx->pos = start_pos + bit_pos;
 	}
 out: