ext4: CVE-2018-1093

ext4: add validity checks for bitmap block numbers

References:
https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/commit/?id=7dac4a1726a9c64a517d595c40e95e2d0d135f6f

Change-Id: I0a523dd7ba303042c8c8ccb336c6816c8a2ef2bd
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>

2 files changed, 109 insertions, 0 deletions

diff --git a/patches/cve/4.9.x.scc b/patches/cve/4.9.x.scc
index 4e5c57f..c97927f 100644
--- a/patches/cve/4.9.x.scc
+++ b/patches/cve/4.9.x.scc
@@ -15,3 +15,6 @@ patch CVE-2018-1130-dccp-check-sk-for-closed-state-in-dccp_sendmsg.patch
 #CVEs fixed in 4.9.96:
 patch CVE-2018-1092-ext4-fail-ext4_iget-for-root-directory-if-unallocate.patch
 patch CVE-2018-1108-random-fix-crng_ready-test.patch
+
+#CVEs fixed in 4.9.98:
+patch CVE-2018-1093-ext4-add-validity-checks-for-bitmap-block-numbers.patch
diff --git a/patches/cve/CVE-2018-1093-ext4-add-validity-checks-for-bitmap-block-numbers.patch b/patches/cve/CVE-2018-1093-ext4-add-validity-checks-for-bitmap-block-numbers.patch
new file mode 100644
index 0000000..d8fcb37
--- /dev/null
+++ b/patches/cve/CVE-2018-1093-ext4-add-validity-checks-for-bitmap-block-numbers.patch
@@ -0,0 +1,106 @@
+From 7dac4a1726a9c64a517d595c40e95e2d0d135f6f Mon Sep 17 00:00:00 2001
+From: Theodore Ts'o <tytso@mit.edu>
+Date: Mon, 26 Mar 2018 23:54:10 -0400
+Subject: [PATCH] ext4: add validity checks for bitmap block numbers
+
+An privileged attacker can cause a crash by mounting a crafted ext4
+image which triggers a out-of-bounds read in the function
+ext4_valid_block_bitmap() in fs/ext4/balloc.c.
+
+This issue has been assigned CVE-2018-1093.
+
+BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=199181
+BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1560782
+Reported-by: Wen Xu <wen.xu@gatech.edu>
+Signed-off-by: Theodore Ts'o <tytso@mit.edu>
+Cc: stable@vger.kernel.org
+
+CVE: CVE-2018-1093   
+Upstream-Status: Backport  
+Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
+---
+ fs/ext4/balloc.c | 16 ++++++++++++++--
+ fs/ext4/ialloc.c |  7 +++++++
+ 2 files changed, 21 insertions(+), 2 deletions(-)
+
+diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
+index f82c496..a33d8fb 100644
+--- a/fs/ext4/balloc.c
++++ b/fs/ext4/balloc.c
+@@ -338,20 +338,25 @@ static ext4_fsblk_t ext4_valid_block_bitmap(struct super_block *sb,
+        /* check whether block bitmap block number is set */
+        blk = ext4_block_bitmap(sb, desc);
+        offset = blk - group_first_block;
+-       if (!ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
++       if (offset < 0 || EXT4_B2C(sbi, offset) >= sb->s_blocksize ||
++           !ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
+                /* bad block bitmap */
+                return blk;
+ 
+        /* check whether the inode bitmap block number is set */
+        blk = ext4_inode_bitmap(sb, desc);
+        offset = blk - group_first_block;
+-       if (!ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
++       if (offset < 0 || EXT4_B2C(sbi, offset) >= sb->s_blocksize ||
++           !ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
+                /* bad block bitmap */
+                return blk;
+ 
+        /* check whether the inode table block number is set */
+        blk = ext4_inode_table(sb, desc);
+        offset = blk - group_first_block;
++       if (offset < 0 || EXT4_B2C(sbi, offset) >= sb->s_blocksize ||
++           EXT4_B2C(sbi, offset + sbi->s_itb_per_group) >= sb->s_blocksize)
++               return blk;
+        next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
+                        EXT4_B2C(sbi, offset + sbi->s_itb_per_group),
+                        EXT4_B2C(sbi, offset));
+@@ -417,6 +422,7 @@ struct buffer_head *
+ ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
+ {
+        struct ext4_group_desc *desc;
++       struct ext4_sb_info *sbi = EXT4_SB(sb);
+        struct buffer_head *bh;
+        ext4_fsblk_t bitmap_blk;
+        int err;
+@@ -425,6 +431,12 @@ ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
+        if (!desc)
+                return ERR_PTR(-EFSCORRUPTED);
+        bitmap_blk = ext4_block_bitmap(sb, desc);
++       if ((bitmap_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
++           (bitmap_blk >= ext4_blocks_count(sbi->s_es))) {
++               ext4_error(sb, "Invalid block bitmap block %llu in "
++                          "block_group %u", bitmap_blk, block_group);
++               return ERR_PTR(-EFSCORRUPTED);
++       }
+        bh = sb_getblk(sb, bitmap_blk);
+        if (unlikely(!bh)) {
+                ext4_error(sb, "Cannot get buffer for block bitmap - "
+diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
+index 3fa9366..df92e3e 100644
+--- a/fs/ext4/ialloc.c
++++ b/fs/ext4/ialloc.c
+@@ -122,6 +122,7 @@ static struct buffer_head *
+ ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group)
+ {
+        struct ext4_group_desc *desc;
++       struct ext4_sb_info *sbi = EXT4_SB(sb);
+        struct buffer_head *bh = NULL;
+        ext4_fsblk_t bitmap_blk;
+        int err;
+@@ -131,6 +132,12 @@ ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group)
+                return ERR_PTR(-EFSCORRUPTED);
+ 
+        bitmap_blk = ext4_inode_bitmap(sb, desc);
++       if ((bitmap_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
++           (bitmap_blk >= ext4_blocks_count(sbi->s_es))) {
++               ext4_error(sb, "Invalid inode bitmap blk %llu in "
++                          "block_group %u", bitmap_blk, block_group);
++               return ERR_PTR(-EFSCORRUPTED);
++       }
+        bh = sb_getblk(sb, bitmap_blk);
+        if (unlikely(!bh)) {
+                ext4_error(sb, "Cannot read inode bitmap - "
+-- 
+2.7.4
+