mke2fs: Avoid crashes / infinite loops for absurdly large devices

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>

diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index d98e71e0d7066e66494329d3aa8a956197da8866..6a83bd9fe2af26f974f0ad0cdfdd2a5dcb5b0334 100644 (file)
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -2089,6 +2089,18 @@ 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);