| From 49d0fe2a14f2a23da2fe299643379b8c1d37df73 Mon Sep 17 00:00:00 2001 |
| From: Theodore Ts'o <tytso@mit.edu> |
| Date: Fri, 6 Feb 2015 12:46:39 -0500 |
| Subject: [PATCH] libext2fs: fix potential buffer overflow in closefs() |
| |
| Upstream-Status: Backport |
| |
| The bug fix in f66e6ce4446: "libext2fs: avoid buffer overflow if |
| s_first_meta_bg is too big" had a typo in the fix for |
| ext2fs_closefs(). In practice most of the security exposure was from |
| the openfs path, since this meant if there was a carefully crafted |
| file system, buffer overrun would be triggered when the file system was |
| opened. |
| |
| However, if corrupted file system didn't trip over some corruption |
| check, and then the file system was modified via tune2fs or debugfs, |
| such that the superblock was marked dirty and then written out via the |
| closefs() path, it's possible that the buffer overrun could be |
| triggered when the file system is closed. |
| |
| Also clear up a signed vs unsigned warning while we're at it. |
| |
| Thanks to Nick Kralevich <nnk@google.com> for asking me to look at |
| compiler warning in the code in question, which led me to notice the |
| bug in f66e6ce4446. |
| |
| Addresses: CVE-2015-1572 |
| |
| Signed-off-by: Theodore Ts'o <tytso@mit.edu> |
| --- |
| lib/ext2fs/closefs.c | 4 ++-- |
| 1 file changed, 2 insertions(+), 2 deletions(-) |
| |
| diff --git a/lib/ext2fs/closefs.c b/lib/ext2fs/closefs.c |
| index 1f99113..ab5b2fb 100644 |
| --- a/lib/ext2fs/closefs.c |
| +++ b/lib/ext2fs/closefs.c |
| @@ -287,7 +287,7 @@ errcode_t ext2fs_flush2(ext2_filsys fs, int flags) |
| dgrp_t j; |
| #endif |
| char *group_ptr; |
| - int old_desc_blocks; |
| + blk64_t old_desc_blocks; |
| struct ext2fs_numeric_progress_struct progress; |
| |
| EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS); |
| @@ -346,7 +346,7 @@ errcode_t ext2fs_flush2(ext2_filsys fs, int flags) |
| group_ptr = (char *) group_shadow; |
| if (fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG) { |
| old_desc_blocks = fs->super->s_first_meta_bg; |
| - if (old_desc_blocks > fs->super->s_first_meta_bg) |
| + if (old_desc_blocks > fs->desc_blocks) |
| old_desc_blocks = fs->desc_blocks; |
| } else |
| old_desc_blocks = fs->desc_blocks; |
| -- |
| 2.1.0 |
| |