From 49d0fe2a14f2a23da2fe299643379b8c1d37df73 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Fri, 6 Feb 2015 12:46:39 -0500 Subject: [PATCH] libext2fs: fix potential buffer overflow in closefs() References: bsc#918346 CVE-2015-1572 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 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 Acked-by: Jan Kara --- 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 1f9911311a1a..ab5b2fb2365e 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; -- 2.1.4