From 71755ee5350b63fb1f283de8561cdb61b47f4d1d Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 2 Aug 2018 08:43:35 -0700
Subject: [PATCH] squashfs: more metadata hardening
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Git-commit: 71755ee5350b63fb1f283de8561cdb61b47f4d1d
Patch-mainline: v4.18-rc8
References: bsc#1051510
The squashfs fragment reading code doesn't actually verify that the
fragment is inside the fragment table. The end result _is_ verified to
be inside the image when actually reading the fragment data, but before
that is done, we may end up taking a page fault because the fragment
table itself might not even exist.
Another report from Anatoly and his endless squashfs image fuzzing.
Reported-by: Анатолий Тросиненко <anatoly.trosinenko@gmail.com>
Acked-by:: Phillip Lougher <phillip.lougher@gmail.com>,
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
fs/squashfs/fragment.c | 13 +++++++++----
fs/squashfs/squashfs_fs_sb.h | 1 +
fs/squashfs/super.c | 5 +++--
3 files changed, 13 insertions(+), 6 deletions(-)
diff --git a/fs/squashfs/fragment.c b/fs/squashfs/fragment.c
index 86ad9a4b8c36..0681feab4a84 100644
--- a/fs/squashfs/fragment.c
+++ b/fs/squashfs/fragment.c
@@ -49,11 +49,16 @@ int squashfs_frag_lookup(struct super_block *sb, unsigned int fragment,
u64 *fragment_block)
{
struct squashfs_sb_info *msblk = sb->s_fs_info;
- int block = SQUASHFS_FRAGMENT_INDEX(fragment);
- int offset = SQUASHFS_FRAGMENT_INDEX_OFFSET(fragment);
- u64 start_block = le64_to_cpu(msblk->fragment_index[block]);
+ int block, offset, size;
struct squashfs_fragment_entry fragment_entry;
- int size;
+ u64 start_block;
+
+ if (fragment >= msblk->fragments)
+ return -EIO;
+ block = SQUASHFS_FRAGMENT_INDEX(fragment);
+ offset = SQUASHFS_FRAGMENT_INDEX_OFFSET(fragment);
+
+ start_block = le64_to_cpu(msblk->fragment_index[block]);
size = squashfs_read_metadata(sb, &fragment_entry, &start_block,
&offset, sizeof(fragment_entry));
diff --git a/fs/squashfs/squashfs_fs_sb.h b/fs/squashfs/squashfs_fs_sb.h
index 1da565cb50c3..ef69c31947bf 100644
--- a/fs/squashfs/squashfs_fs_sb.h
+++ b/fs/squashfs/squashfs_fs_sb.h
@@ -75,6 +75,7 @@ struct squashfs_sb_info {
unsigned short block_log;
long long bytes_used;
unsigned int inodes;
+ unsigned int fragments;
int xattr_ids;
};
#endif
diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c
index 8a73b97217c8..40e657386fa5 100644
--- a/fs/squashfs/super.c
+++ b/fs/squashfs/super.c
@@ -175,6 +175,7 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
msblk->inode_table = le64_to_cpu(sblk->inode_table_start);
msblk->directory_table = le64_to_cpu(sblk->directory_table_start);
msblk->inodes = le32_to_cpu(sblk->inodes);
+ msblk->fragments = le32_to_cpu(sblk->fragments);
flags = le16_to_cpu(sblk->flags);
TRACE("Found valid superblock on %pg\n", sb->s_bdev);
@@ -185,7 +186,7 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
TRACE("Filesystem size %lld bytes\n", msblk->bytes_used);
TRACE("Block size %d\n", msblk->block_size);
TRACE("Number of inodes %d\n", msblk->inodes);
- TRACE("Number of fragments %d\n", le32_to_cpu(sblk->fragments));
+ TRACE("Number of fragments %d\n", msblk->fragments);
TRACE("Number of ids %d\n", le16_to_cpu(sblk->no_ids));
TRACE("sblk->inode_table_start %llx\n", msblk->inode_table);
TRACE("sblk->directory_table_start %llx\n", msblk->directory_table);
@@ -272,7 +273,7 @@ static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
sb->s_export_op = &squashfs_export_ops;
handle_fragments:
- fragments = le32_to_cpu(sblk->fragments);
+ fragments = msblk->fragments;
if (fragments == 0)
goto check_directory_table;
--
2.19.0