From 8dbe7b475ec5e91ed767239f0e85880f416fc384 Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso@mit.edu>
Date: Sun, 1 Sep 2019 00:59:16 -0400
Subject: [PATCH] libsupport: add checks to prevent buffer overrun bugs in
 quota code

A maliciously corrupted file systems can trigger buffer overruns in
the quota code used by e2fsck.  To fix this, add sanity checks to the
quota header fields as well as to block number references in the quota
tree.

Addresses: CVE-2019-5094
Addresses: TALOS-2019-0887
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---
 lib/support/mkquota.c      |  1 +
 lib/support/quotaio_tree.c | 71 ++++++++++++++++++++++++++++++----------------
 lib/support/quotaio_v2.c   | 28 ++++++++++++++++++
 3 files changed, 76 insertions(+), 24 deletions(-)

diff --git a/lib/support/mkquota.c b/lib/support/mkquota.c
index 0b9e766..ddb5312 100644
--- a/lib/support/mkquota.c
+++ b/lib/support/mkquota.c
@@ -671,6 +671,7 @@ errcode_t quota_compare_and_update(quota_ctx_t qctx, enum quota_type qtype,
 	err = qh.qh_ops->scan_dquots(&qh, scan_dquots_callback, &scan_data);
 	if (err) {
 		log_debug("Error scanning dquots");
+		*usage_inconsistent = 1;
 		goto out_close_qh;
 	}
 
diff --git a/lib/support/quotaio_tree.c b/lib/support/quotaio_tree.c
index a7c2028..6cc4fb5 100644
--- a/lib/support/quotaio_tree.c
+++ b/lib/support/quotaio_tree.c
@@ -540,6 +540,17 @@ struct dquot *qtree_read_dquot(struct quota_handle *h, qid_t id)
 	return dquot;
 }
 
+static int check_reference(struct quota_handle *h, unsigned int blk)
+{
+	if (blk >= h->qh_info.u.v2_mdqi.dqi_qtree.dqi_blocks) {
+		log_err("Illegal reference (%u >= %u) in %s quota file",
+			blk, h->qh_info.u.v2_mdqi.dqi_qtree.dqi_blocks,
+			quota_type2name(h->qh_type));
+		return -1;
+	}
+	return 0;
+}
+
 /*
  * Scan all dquots in file and call callback on each
  */
@@ -558,7 +569,7 @@ static int report_block(struct dquot *dquot, unsigned int blk, char *bitmap,
 	int entries, i;
 
 	if (!buf)
-		return 0;
+		return -1;
 
 	set_bit(bitmap, blk);
 	read_blk(dquot->dq_h, blk, buf);
@@ -580,23 +591,12 @@ static int report_block(struct dquot *dquot, unsigned int blk, char *bitmap,
 	return entries;
 }
 
-static void check_reference(struct quota_handle *h, unsigned int blk)
-{
-	if (blk >= h->qh_info.u.v2_mdqi.dqi_qtree.dqi_blocks)
-		log_err("Illegal reference (%u >= %u) in %s quota file. "
-			"Quota file is probably corrupted.\n"
-			"Please run e2fsck (8) to fix it.",
-			blk,
-			h->qh_info.u.v2_mdqi.dqi_qtree.dqi_blocks,
-			quota_type2name(h->qh_type));
-}
-
 static int report_tree(struct dquot *dquot, unsigned int blk, int depth,
 		       char *bitmap,
 		       int (*process_dquot) (struct dquot *, void *),
 		       void *data)
 {
-	int entries = 0, i;
+	int entries = 0, ret, i;
 	dqbuf_t buf = getdqbuf();
 	__le32 *ref = (__le32 *) buf;
 
@@ -607,22 +607,40 @@ static int report_tree(struct dquot *dquot, unsigned int blk, int depth,
 	if (depth == QT_TREEDEPTH - 1) {
 		for (i = 0; i < QT_BLKSIZE >> 2; i++) {
 			blk = ext2fs_le32_to_cpu(ref[i]);
-			check_reference(dquot->dq_h, blk);
-			if (blk && !get_bit(bitmap, blk))
-				entries += report_block(dquot, blk, bitmap,
-							process_dquot, data);
+			if (check_reference(dquot->dq_h, blk)) {
+				entries = -1;
+				goto errout;
+			}
+			if (blk && !get_bit(bitmap, blk)) {
+				ret = report_block(dquot, blk, bitmap,
+						   process_dquot, data);
+				if (ret < 0) {
+					entries = ret;
+					goto errout;
+				}
+				entries += ret;
+			}
 		}
 	} else {
 		for (i = 0; i < QT_BLKSIZE >> 2; i++) {
 			blk = ext2fs_le32_to_cpu(ref[i]);
 			if (blk) {
-				check_reference(dquot->dq_h, blk);
-				entries += report_tree(dquot, blk, depth + 1,
-						       bitmap, process_dquot,
-						       data);
+				if (check_reference(dquot->dq_h, blk)) {
+					entries = -1;
+					goto errout;
+				}
+				ret = report_tree(dquot, blk, depth + 1,
+						  bitmap, process_dquot,
+						  data);
+				if (ret < 0) {
+					entries = ret;
+					goto errout;
+				}
+				entries += ret;
 			}
 		}
 	}
+errout:
 	freedqbuf(buf);
 	return entries;
 }
@@ -642,6 +660,7 @@ int qtree_scan_dquots(struct quota_handle *h,
 		      int (*process_dquot) (struct dquot *, void *),
 		      void *data)
 {
+	int ret;
 	char *bitmap;
 	struct v2_mem_dqinfo *v2info = &h->qh_info.u.v2_mdqi;
 	struct qtree_mem_dqinfo *info = &v2info->dqi_qtree;
@@ -655,10 +674,14 @@ int qtree_scan_dquots(struct quota_handle *h,
 		ext2fs_free_mem(&dquot);
 		return -1;
 	}
-	v2info->dqi_used_entries = report_tree(dquot, QT_TREEOFF, 0, bitmap,
-					       process_dquot, data);
+	ret = report_tree(dquot, QT_TREEOFF, 0, bitmap, process_dquot, data);
+	if (ret < 0)
+		goto errout;
+	v2info->dqi_used_entries = ret;
 	v2info->dqi_data_blocks = find_set_bits(bitmap, info->dqi_blocks);
+	ret = 0;
+errout:
 	ext2fs_free_mem(&bitmap);
 	ext2fs_free_mem(&dquot);
-	return 0;
+	return ret;
 }
diff --git a/lib/support/quotaio_v2.c b/lib/support/quotaio_v2.c
index 38be2a3..7390667 100644
--- a/lib/support/quotaio_v2.c
+++ b/lib/support/quotaio_v2.c
@@ -175,6 +175,8 @@ static int v2_check_file(struct quota_handle *h, int type, int fmt)
 static int v2_init_io(struct quota_handle *h)
 {
 	struct v2_disk_dqinfo ddqinfo;
+	struct v2_mem_dqinfo *info;
+	__u64 filesize;
 
 	h->qh_info.u.v2_mdqi.dqi_qtree.dqi_entry_size =
 		sizeof(struct v2r1_disk_dqblk);
@@ -185,6 +187,32 @@ static int v2_init_io(struct quota_handle *h)
 			 sizeof(ddqinfo)) != sizeof(ddqinfo))
 		return -1;
 	v2_disk2memdqinfo(&h->qh_info, &ddqinfo);
+
+	/* Check to make sure quota file info is sane */
+	info = &h->qh_info.u.v2_mdqi;
+	if (ext2fs_file_get_lsize(h->qh_qf.e2_file, &filesize))
+		return -1;
+	if ((filesize > (1U << 31)) ||
+	    (info->dqi_qtree.dqi_blocks >
+	     (filesize + QT_BLKSIZE - 1) >> QT_BLKSIZE_BITS)) {
+		log_err("Quota inode %u corrupted: file size %llu; "
+			"dqi_blocks %u", h->qh_qf.ino,
+			filesize, info->dqi_qtree.dqi_blocks);
+		return -1;
+	}
+	if (info->dqi_qtree.dqi_free_blk >= info->dqi_qtree.dqi_blocks) {
+		log_err("Quota inode %u corrupted: free_blk %u; dqi_blocks %u",
+			h->qh_qf.ino, info->dqi_qtree.dqi_free_blk,
+			info->dqi_qtree.dqi_blocks);
+		return -1;
+	}
+	if (info->dqi_qtree.dqi_free_entry >= info->dqi_qtree.dqi_blocks) {
+		log_err("Quota inode %u corrupted: free_entry %u; "
+			"dqi_blocks %u", h->qh_qf.ino,
+			info->dqi_qtree.dqi_free_entry,
+			info->dqi_qtree.dqi_blocks);
+		return -1;
+	}
 	return 0;
 }
 
-- 
1.8.3.1

