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From ff6679208f45975a090b1260367f1fc5a17b3db7 Mon Sep 17 00:00:00 2001
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From: Lukas Czerner <lczerner@redhat.com>
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Date: Thu, 21 Apr 2022 19:31:48 +0200
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Subject: [PATCH] libext2fs: add sanity check to extent manipulation
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Content-Type: text/plain
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It is possible to have a corrupted extent tree in such a way that a leaf
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node contains zero extents in it. Currently if that happens and we try
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to traverse the tree we can end up accessing wrong data, or possibly
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even uninitialized memory. Make sure we don't do that.
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Additionally make sure that we have a sane number of bytes passed to
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memmove() in ext2fs_extent_delete().
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Note that e2fsck is currently unable to spot and fix such corruption in
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pass1.
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Signed-off-by: Lukas Czerner <lczerner@redhat.com>
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Reported-by: Nils Bars <nils_bars@t-online.de>
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Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=2068113
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Addresses: CVE-2022-1304
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Addresses-Debian-Bug: #1010263
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Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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(cherry picked from commit ab51d587bb9b229b1fade1afd02e1574c1ba5c76)
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---
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lib/ext2fs/extent.c | 8 ++++++++
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1 file changed, 8 insertions(+)
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diff --git a/lib/ext2fs/extent.c b/lib/ext2fs/extent.c
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index b324c7b0..1a206a16 100644
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--- a/lib/ext2fs/extent.c
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+++ b/lib/ext2fs/extent.c
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@@ -495,6 +495,10 @@ retry:
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ext2fs_le16_to_cpu(eh->eh_entries);
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newpath->max_entries = ext2fs_le16_to_cpu(eh->eh_max);
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+ /* Make sure there is at least one extent present */
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+ if (newpath->left <= 0)
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+ return EXT2_ET_EXTENT_NO_DOWN;
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+
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if (path->left > 0) {
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ix++;
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newpath->end_blk = ext2fs_le32_to_cpu(ix->ei_block);
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@@ -1630,6 +1634,10 @@ errcode_t ext2fs_extent_delete(ext2_extent_handle_t handle, int flags)
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cp = path->curr;
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+ /* Sanity check before memmove() */
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+ if (path->left < 0)
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+ return EXT2_ET_EXTENT_LEAF_BAD;
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+
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if (path->left) {
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memmove(cp, cp + sizeof(struct ext3_extent_idx),
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path->left * sizeof(struct ext3_extent_idx));
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--
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2.35.3
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