From 01cfb7937a9af2abb1136c7e89fbf3fd92952956 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Sun, 29 Jul 2018 12:44:46 -0700
Subject: [PATCH] squashfs: be more careful about metadata corruption
Git-commit: 01cfb7937a9af2abb1136c7e89fbf3fd92952956
Patch-mainline: v4.18-rc7
References: bsc#1051510
Anatoly Trosinenko reports that a corrupted squashfs image can cause a
kernel oops. It turns out that squashfs can end up being confused about
negative fragment lengths.
The regular squashfs_read_data() does check for negative lengths, but
squashfs_read_metadata() did not, and the fragment size code just
blindly trusted the on-disk value. Fix both the fragment parsing and
the metadata reading code.
Reported-by: Anatoly Trosinenko <anatoly.trosinenko@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Phillip Lougher <phillip@squashfs.org.uk>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
fs/squashfs/cache.c | 3 +++
fs/squashfs/file.c | 8 ++++++--
fs/squashfs/fragment.c | 4 +---
fs/squashfs/squashfs_fs.h | 6 ++++++
4 files changed, 16 insertions(+), 5 deletions(-)
diff --git a/fs/squashfs/cache.c b/fs/squashfs/cache.c
index 23813c078cc9..0839efa720b3 100644
--- a/fs/squashfs/cache.c
+++ b/fs/squashfs/cache.c
@@ -350,6 +350,9 @@ int squashfs_read_metadata(struct super_block *sb, void *buffer,
TRACE("Entered squashfs_read_metadata [%llx:%x]\n", *block, *offset);
+ if (unlikely(length < 0))
+ return -EIO;
+
while (length) {
entry = squashfs_cache_get(sb, msblk->block_cache, *block, 0);
if (entry->error) {
diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c
index 13d80947bf9e..fcff2e0487fe 100644
--- a/fs/squashfs/file.c
+++ b/fs/squashfs/file.c
@@ -194,7 +194,11 @@ static long long read_indexes(struct super_block *sb, int n,
}
for (i = 0; i < blocks; i++) {
- int size = le32_to_cpu(blist[i]);
+ int size = squashfs_block_size(blist[i]);
+ if (size < 0) {
+ err = size;
+ goto failure;
+ }
block += SQUASHFS_COMPRESSED_SIZE_BLOCK(size);
}
n -= blocks;
@@ -367,7 +371,7 @@ static int read_blocklist(struct inode *inode, int index, u64 *block)
sizeof(size));
if (res < 0)
return res;
- return le32_to_cpu(size);
+ return squashfs_block_size(size);
}
/* Copy data into page cache */
diff --git a/fs/squashfs/fragment.c b/fs/squashfs/fragment.c
index 0ed6edbc5c71..86ad9a4b8c36 100644
--- a/fs/squashfs/fragment.c
+++ b/fs/squashfs/fragment.c
@@ -61,9 +61,7 @@ int squashfs_frag_lookup(struct super_block *sb, unsigned int fragment,
return size;
*fragment_block = le64_to_cpu(fragment_entry.start_block);
- size = le32_to_cpu(fragment_entry.size);
-
- return size;
+ return squashfs_block_size(fragment_entry.size);
}
diff --git a/fs/squashfs/squashfs_fs.h b/fs/squashfs/squashfs_fs.h
index 24d12fd14177..4e6853f084d0 100644
--- a/fs/squashfs/squashfs_fs.h
+++ b/fs/squashfs/squashfs_fs.h
@@ -129,6 +129,12 @@
#define SQUASHFS_COMPRESSED_BLOCK(B) (!((B) & SQUASHFS_COMPRESSED_BIT_BLOCK))
+static inline int squashfs_block_size(__le32 raw)
+{
+ u32 size = le32_to_cpu(raw);
+ return (size >> 25) ? -EIO : size;
+}
+
/*
* Inode number ops. Inodes consist of a compressed block number, and an
* uncompressed offset within that block
--
2.19.0