xz_dec_run() could incorrectly return XZ_BUF_ERROR if all of the
following was true:
- The caller knows how many bytes of output to expect and only provides
that much output space.
- When the last output bytes are decoded, the caller-provided input
buffer ends right before the LZMA2 end of payload marker. So LZMA2
won't provide more output anymore, but it won't know it yet and thus
won't return XZ_STREAM_END yet.
- A BCJ filter is in use and it hasn't left any unfiltered bytes in the
temp buffer. This can happen with any BCJ filter, but in practice
it's more likely with filters other than the x86 BCJ.
This fixes <https://bugzilla.redhat.com/show_bug.cgi?id=735408> where
Squashfs thinks that a valid file system is corrupt.
This also fixes a similar bug in single-call mode where the uncompressed
size of a block using BCJ + LZMA2 was 0 bytes and caller provided no
output space. Many empty .xz files don't contain any blocks and thus
don't trigger this bug.
This also tweaks a closely related detail: xz_dec_bcj_run() could call
xz_dec_lzma2_run() to decode into temp buffer when it was known to be
useless. This was harmless although it wasted a minuscule number of CPU
cycles.
Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
Cc: stable <stable@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In userspace, the .lzma format has become mostly a legacy file format that
got superseded by the .xz format. Similarly, LZMA Utils was superseded by
XZ Utils.
These patches add support for XZ decompression into the kernel. Most of
the code is as is from XZ Embedded <http://tukaani.org/xz/embedded.html>.
It was written for the Linux kernel but is usable in other projects too.
Advantages of XZ over the current LZMA code in the kernel:
- Nice API that can be used by other kernel modules; it's
not limited to kernel, initramfs, and initrd decompression.
- Integrity check support (CRC32)
- BCJ filters improve compression of executable code on
certain architectures. These together with LZMA2 can
produce a few percent smaller kernel or Squashfs images
than plain LZMA without making the decompression slower.
This patch: Add the main decompression code (xz_dec), testing module
(xz_dec_test), wrapper script (xz_wrap.sh) for the xz command line tool,
and documentation. The xz_dec module is enough to have a usable XZ
decompressor e.g. for Squashfs.
Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alain Knaff <alain@knaff.lu>
Cc: Albin Tonnerre <albin.tonnerre@free-electrons.com>
Cc: Phillip Lougher <phillip@lougher.demon.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Lasse Collin