From f7da56758e5d15416339d640f79d6eee875d22a9 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Tue, 25 Oct 2016 14:08:59 -0400
Subject: [PATCH 09/16] mke2fs: Avoid crashes / infinite loops for absurdly
 large devices

commit 101ef2e93c253ae62320628e8958067d2d2a4e2a

When a device reports absurdly high size, some arithmetics in mke2fs can
overflow (e.g. number of block descriptors) and we end in an infinite
loop. Fix that by checking and refusing insanely large devices.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---
 misc/mke2fs.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index 2787a127..7cea0330 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -1858,6 +1858,18 @@ profile_error:
 			EXT2_BLOCK_SIZE(&fs_param));
 		exit(1);
 	}
+	/*
+	 * Guard against group descriptor count overflowing... Mostly to avoid
+	 * strange results for absurdly large devices.
+	 */
+	if (fs_blocks_count > ((1ULL << (fs_param.s_log_block_size + 3 + 32)) - 1)) {
+		fprintf(stderr, _("%s: Size of device (0x%llx blocks) %s "
+				  "too big to create\n\t"
+				  "a filesystem using a blocksize of %d.\n"),
+			program_name, fs_blocks_count, device_name,
+			EXT2_BLOCK_SIZE(&fs_param));
+		exit(1);
+	}
 
 	ext2fs_blocks_count_set(&fs_param, fs_blocks_count);
 
-- 
2.20.1