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!201 [sync] PR-200: fs/minix: Avoid mistakenly probing ext2 filesystems

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From: @openeuler-sync-bot 
Reviewed-by: @t_feng 
Signed-off-by: @t_feng
This commit is contained in:
openeuler-ci-bot 2022-12-09 09:54:02 +00:00 committed by Gitee
commit 273df661b8
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GPG Key ID: 173E9B9CA92EEF8F
3 changed files with 88 additions and 1 deletions
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80
backport-fs-minix-Avoid-mistakenly-probing-ext2-filesystems.patch Normal file
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@ -0,0 +1,80 @@
From 25d64bb273c09d6346c0703b378f6e4f1d6d67c2 Mon Sep 17 00:00:00 2001
From: Daniel Drake <drake@endlessm.com>
Date: Fri, 12 Mar 2021 12:05:08 -0600
Subject: [PATCH] fs/minix: Avoid mistakenly probing ext2 filesystems
The ext2 (and ext3, ext4) filesystems write the number of free inodes to
location 0x410.
On a MINIX filesystem, that same location is used for the MINIX superblock
magic number.
If the number of free inodes on an ext2 filesystem is equal to any
of the four MINIX superblock magic values plus any multiple of 65536,
GRUB's MINIX filesystem code will probe it as a MINIX filesystem.
In the case of an OS using ext2 as the root filesystem, since there will
ordinarily be some amount of file creation and deletion on every bootup,
it effectively means that this situation has a 1:16384 chance of being hit
on every reboot.
This will cause GRUB's filesystem probing code to mistakenly identify an
ext2 filesystem as MINIX. This can be seen by e.g. "search --label"
incorrectly indicating that no such ext2 partition with matching label
exists, whereas in fact it does.
After spotting the rough cause of the issue I was facing here, I borrowed
much of the diagnosis/explanation from meierfra who found and investigated
the same issue in util-linux in 2010:
https://bugs.launchpad.net/ubuntu/+source/util-linux/+bug/518582
This was fixed in util-linux by having the MINIX code check for the
ext2 magic. Do the same here.
Signed-off-by: Daniel Drake <drake@endlessm.com>
Reviewed-by: Derek Foreman <derek@endlessos.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
grub-core/fs/minix.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/grub-core/fs/minix.c b/grub-core/fs/minix.c
index d0d08363c..3cd18c85b 100644
--- a/grub-core/fs/minix.c
+++ b/grub-core/fs/minix.c
@@ -38,6 +38,8 @@ GRUB_MOD_LICENSE ("GPLv3+");
#define GRUB_MINIX_MAGIC_30 0x138F
#endif
+#define EXT2_MAGIC 0xEF53
+
#define GRUB_MINIX_INODE_DIR_BLOCKS 7
#define GRUB_MINIX_LOG2_BSIZE 1
#define GRUB_MINIX_ROOT_INODE 1
@@ -466,7 +468,21 @@ grub_minix_find_file (struct grub_minix_data *data, const char *path)
static struct grub_minix_data *
grub_minix_mount (grub_disk_t disk)
{
- struct grub_minix_data *data;
+ struct grub_minix_data *data = NULL;
+ grub_uint16_t ext2_marker;
+
+ grub_disk_read (disk, 2, 56, sizeof (ext2_marker), &ext2_marker);
+ if (grub_errno != GRUB_ERR_NONE)
+ goto fail;
+
+ /*
+ * The ext2 filesystems can sometimes be mistakenly identified as MINIX, e.g.
+ * due to the number of free ext2 inodes being written to the same location
+ * where the MINIX superblock magic is found. Avoid such situations by
+ * skipping any filesystems that have the ext2 superblock magic.
+ */
+ if (ext2_marker == grub_cpu_to_le16_compile_time (EXT2_MAGIC))
+ goto fail;
data = grub_malloc (sizeof (struct grub_minix_data));
if (!data)
--
2.27.0

1
grub.patches
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@ -422,3 +422,4 @@ Patch0421: backport-font-Fix-an-integer-underflow-in-blit_comb.patch
Patch0422: backport-font-Harden-grub_font_blit_glyph-and-grub_font_blit_.patch
Patch0423: backport-font-Assign-null_font-to-glyphs-in-ascii_font_glyph.patch
Patch0424: backport-normal-charset-Fix-an-integer-overflow-in-grub_unico.patch
Patch0425: backport-fs-minix-Avoid-mistakenly-probing-ext2-filesystems.patch

8
grub2.spec
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@ -8,7 +8,7 @@
Name: grub2
Epoch: 1
Version: 2.04
Release: 26
Release: 27
Summary: Bootloader with support for Linux, Multiboot and more
License: GPLv3+
URL: http://www.gnu.org/software/grub/
@ -450,6 +450,12 @@ rm -r /boot/grub2.tmp/ || :
%{_datadir}/man/man*
%changelog
* Fri Dec 9 2022 zhangqiumiao <zhangqiumiao1@huawei.com> - 1:2.04-27
- Type:bugfix
- CVE:NA
- SUG:NA
- DESC:fs/minix: Avoid mistakenly probing ext2 filesystems
* Fri Nov 18 2022 zhangqiumiao <zhangqiumiao1@huawei.com> - 1:2.04-26
- Type:CVE
- CVE:CVE-2022-2601 CVE-2022-3775