A Sysbot [1] corrupted filesystem exposes two flaws in the handling and
sanity checking of the xattr_ids count in the filesystem. Both of these
flaws cause computation overflow due to incorrect typing.
In the corrupted filesystem the xattr_ids value is 4294967071, which
stored in a signed variable becomes the negative number -225.
Flaw 1 (64-bit systems only):
The signed integer xattr_ids variable causes sign extension.
This causes variable overflow in the SQUASHFS_XATTR_*(A) macros. The
variable is first multiplied by sizeof(struct squashfs_xattr_id) where the
type of the sizeof operator is "unsigned long".
On a 64-bit system this is 64-bits in size, and causes the negative number
to be sign extended and widened to 64-bits and then become unsigned. This
produces the very large number 18446744073709548016 or 2^64 - 3600. This
number when rounded up by SQUASHFS_METADATA_SIZE - 1 (8191 bytes) and
divided by SQUASHFS_METADATA_SIZE overflows and produces a length of 0
(stored in len).
Flaw 2 (32-bit systems only):
On a 32-bit system the integer variable is not widened by the unsigned
long type of the sizeof operator (32-bits), and the signedness of the
variable has no effect due it always being treated as unsigned.
The above corrupted xattr_ids value of 4294967071, when multiplied
overflows and produces the number 4294963696 or 2^32 - 3400. This number
when rounded up by SQUASHFS_METADATA_SIZE - 1 (8191 bytes) and divided by
SQUASHFS_METADATA_SIZE overflows again and produces a length of 0.
The effect of the 0 length computation:
In conjunction with the corrupted xattr_ids field, the filesystem also has
a corrupted xattr_table_start value, where it matches the end of
filesystem value of 850.
This causes the following sanity check code to fail because the
incorrectly computed len of 0 matches the incorrect size of the table
reported by the superblock (0 bytes).
len = SQUASHFS_XATTR_BLOCK_BYTES(*xattr_ids);
indexes = SQUASHFS_XATTR_BLOCKS(*xattr_ids);
/*
* The computed size of the index table (len bytes) should exactly
* match the table start and end points
*/
start = table_start + sizeof(*id_table);
end = msblk->bytes_used;
if (len != (end - start))
return ERR_PTR(-EINVAL);
Changing the xattr_ids variable to be "usigned int" fixes the flaw on a
64-bit system. This relies on the fact the computation is widened by the
unsigned long type of the sizeof operator.
Casting the variable to u64 in the above macro fixes this flaw on a 32-bit
system.
It also means 64-bit systems do not implicitly rely on the type of the
sizeof operator to widen the computation.
[1] https://lore.kernel.org/lkml/000000000000cd44f005f1a0f17f@google.com/
Link: https://lkml.kernel.org/r/20230127061842.10965-1-phillip@squashfs.org.uk
Fixes: 506220d2ba ("squashfs: add more sanity checks in xattr id lookup")
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Reported-by: <syzbot+082fa4af80a5bb1a9843@syzkaller.appspotmail.com>
Cc: Alexey Khoroshilov <khoroshilov@ispras.ru>
Cc: Fedor Pchelkin <pchelkin@ispras.ru>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When mouting a squashfs image created without inode compression it fails
with: "unable to read inode lookup table"
It turns out that the BLOCK_OFFSET is missing when checking the
SQUASHFS_METADATA_SIZE agaist the actual size.
Link: https://lkml.kernel.org/r/20210226092903.1473545-1-sean@geanix.com
Fixes: eabac19e40 ("squashfs: add more sanity checks in inode lookup")
Signed-off-by: Sean Nyekjaer <sean@geanix.com>
Acked-by: Phillip Lougher <phillip@squashfs.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There is a regular need in the kernel to provide a way to declare having a
dynamically sized set of trailing elements in a structure. Kernel code should
always use “flexible array members”[1] for these cases. The older style of
one-element or zero-length arrays should no longer be used[2].
[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://github.com/KSPP/linux/issues/21
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Based on 1 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 or at your option any
later version this program is distributed in the hope that it will
be useful but without any warranty without even the implied warranty
of merchantability or fitness for a particular purpose see the gnu
general public license for more details you should have received a
copy of the gnu general public license along with this program if
not write to the free software foundation 51 franklin street fifth
floor boston ma 02110 1301 usa
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-or-later
has been chosen to replace the boilerplate/reference in 23 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190520170857.458548087@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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>
Add zstd compression and decompression support to SquashFS. zstd is a
great fit for SquashFS because it can compress at ratios approaching xz,
while decompressing twice as fast as zlib. For SquashFS in particular,
it can decompress as fast as lzo and lz4. It also has the flexibility
to turn down the compression ratio for faster compression times.
The compression benchmark is run on the file tree from the SquashFS archive
found in ubuntu-16.10-desktop-amd64.iso [1]. It uses `mksquashfs` with the
default block size (128 KB) and and various compression algorithms/levels.
xz and zstd are also benchmarked with 256 KB blocks. The decompression
benchmark times how long it takes to `tar` the file tree into `/dev/null`.
See the benchmark file in the upstream zstd source repository located under
`contrib/linux-kernel/squashfs-benchmark.sh` [2] for details.
I ran the benchmarks on a Ubuntu 14.04 VM with 2 cores and 4 GiB of RAM.
The VM is running on a MacBook Pro with a 3.1 GHz Intel Core i7 processor,
16 GB of RAM, and a SSD.
| Method | Ratio | Compression MB/s | Decompression MB/s |
|----------------|-------|------------------|--------------------|
| gzip | 2.92 | 15 | 128 |
| lzo | 2.64 | 9.5 | 217 |
| lz4 | 2.12 | 94 | 218 |
| xz | 3.43 | 5.5 | 35 |
| xz 256 KB | 3.53 | 5.4 | 40 |
| zstd 1 | 2.71 | 96 | 210 |
| zstd 5 | 2.93 | 69 | 198 |
| zstd 10 | 3.01 | 41 | 225 |
| zstd 15 | 3.13 | 11.4 | 224 |
| zstd 16 256 KB | 3.24 | 8.1 | 210 |
This patch was written by Sean Purcell <me@seanp.xyz>, but I will be
taking over the submission process.
[1] http://releases.ubuntu.com/16.10/
[2] https://github.com/facebook/zstd/blob/dev/contrib/linux-kernel/squashfs-benchmark.sh
zstd source repository: https://github.com/facebook/zstd
Signed-off-by: Sean Purcell <me@seanp.xyz>
Signed-off-by: Nick Terrell <terrelln@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
Acked-by: Phillip Lougher <phillip@squashfs.org.uk>
Add support for reading file systems compressed with the
LZ4 compression algorithm.
This patch adds the LZ4 decompressor wrapper code.
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
We read the type field from disk. This value should be sanity
checked for correctness to avoid an out of bounds access when
reading the squashfs_filetype_table array.
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Most of these were never used by the kernel code, but belong to
the time when the header file was used by both the kernel code
and the user space tools.
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Its better to use defined name instead of constant
Signed-off-by: Ajeet Yadav <ajeet.yadav.77@gmail.com>
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
This commit adds an option to set the device block size used to 4K.
By default Squashfs sets the device block size (sb_min_blocksize) to 1K
or the smallest block size supported by the block device (if larger).
This, because blocks are packed together and unaligned in Squashfs,
should reduce latency.
This, however, gives poor performance on MTD NAND devices where
the optimal I/O size is 4K (even though the devices can support
smaller block sizes).
Using a 4K device block size may also improve overall I/O
performance for some file access patterns (e.g. sequential
accesses of files in filesystem order) on all media.
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
My existing email address may stop working in a month or two, so update
email to one that will continue working.
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
Extend decompressor framework to handle compression options stored in
the filesystem. These options can be used by the relevant decompressor
at initialisation time to over-ride defaults.
The presence of compression options in the filesystem is indicated by
the COMP_OPT filesystem flag. If present the data is read from the
filesystem and passed to the decompressor init function. The decompressor
init function signature has been extended to take this data.
Also update the init function signature in the glib, lzo and xz
decompressor wrappers.
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
Add support for reading file systems compressed with the
XZ compression algorithm.
This patch adds the XZ decompressor wrapper code.
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
Add new extended inode types that store the xattr_id field.
Also add the necessary code changes to make xattrs visibile.
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
This patch adds support for mapping xattr ids (stored in inodes)
into the on-disk location of the xattrs themselves.
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
Add knowledge of lzma/lzo compression formats to the decompressor
framework. For now these are added as unsupported. Without
these entries lzma/lzo compressed filesystems will be flagged as
having unknown compression which is undesirable.
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
Use the standard magic.h for btrfs and squashfs.
Signed-off-by: Qinghuang Feng <qhfeng.kernel@gmail.com>
Cc: Phillip Lougher <phillip@lougher.demon.co.uk>
Cc: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
