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commit 49d0fe2a14f2a23da2fe299643379b8c1d37df73
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Author: Theodore Ts'o <tytso@mit.edu>
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Date: Fri Feb 6 12:46:39 2015 -0500
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libext2fs: fix potential buffer overflow in closefs()
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The bug fix in f66e6ce4446: "libext2fs: avoid buffer overflow if
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s_first_meta_bg is too big" had a typo in the fix for
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ext2fs_closefs(). In practice most of the security exposure was from
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the openfs path, since this meant if there was a carefully crafted
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file system, buffer overrun would be triggered when the file system was
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opened.
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However, if corrupted file system didn't trip over some corruption
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check, and then the file system was modified via tune2fs or debugfs,
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such that the superblock was marked dirty and then written out via the
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closefs() path, it's possible that the buffer overrun could be
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triggered when the file system is closed.
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Also clear up a signed vs unsigned warning while we're at it.
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Thanks to Nick Kralevich <nnk@google.com> for asking me to look at
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compiler warning in the code in question, which led me to notice the
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bug in f66e6ce4446.
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Addresses: CVE-2015-1572
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Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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Index: e2fsprogs-1.42.9/lib/ext2fs/closefs.c
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===================================================================
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--- e2fsprogs-1.42.9.orig/lib/ext2fs/closefs.c
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+++ e2fsprogs-1.42.9/lib/ext2fs/closefs.c
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@@ -279,7 +279,7 @@ errcode_t ext2fs_flush2(ext2_filsys fs,
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dgrp_t j;
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#endif
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char *group_ptr;
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- int old_desc_blocks;
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+ blk64_t old_desc_blocks;
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struct ext2fs_numeric_progress_struct progress;
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EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
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@@ -338,7 +338,7 @@ errcode_t ext2fs_flush2(ext2_filsys fs,
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group_ptr = (char *) group_shadow;
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if (fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG) {
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old_desc_blocks = fs->super->s_first_meta_bg;
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- if (old_desc_blocks > fs->super->s_first_meta_bg)
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+ if (old_desc_blocks > fs->desc_blocks)
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old_desc_blocks = fs->desc_blocks;
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} else
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old_desc_blocks = fs->desc_blocks;
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