Commit b11ed18e authored by Dave Rodgman's avatar Dave Rodgman Committed by Linus Torvalds
Browse files

lib/lzo: fix bugs for very short or empty input 

For very short input data (0 - 1 bytes), lzo-rle was not behaving
correctly.  Fix this behaviour and update documentation accordingly.

For zero-length input, lzo v0 outputs an end-of-stream marker only,
which was misinterpreted by lzo-rle as a bitstream version number.
Ensure bitstream versions > 0 require a minimum stream length of 5.

Also fixes a bug in handling the tail for very short inputs when a
bitstream version is present.

Link: http://lkml.kernel.org/r/20190326165857.34613-1-dave.rodgman@arm.com


Signed-off-by: default avatarDave Rodgman <dave.rodgman@arm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6147e136

Documentation/lzo.txt

+5 −3
Original line number Diff line number Diff line
@@ -102,9 +102,11 @@ Byte sequences 
                dictionary which is empty, and that it will always be

                invalid at this place.



      17      : bitstream version. If the first byte is 17, the next byte

                gives the bitstream version (version 1 only). If the first byte

                is not 17, the bitstream version is 0.

      17      : bitstream version. If the first byte is 17, and compressed

                stream length is at least 5 bytes (length of shortest possible

                versioned bitstream), the next byte gives the bitstream version

                (version 1 only).

                Otherwise, the bitstream version is 0.



      18..21  : copy 0..3 literals

                state = (byte - 17) = 0..3  [ copy <state> literals ]

lib/lzo/lzo1x_compress.c

+6 −3
Original line number Diff line number Diff line
@@ -291,13 +291,14 @@ int lzogeneric1x_1_compress(const unsigned char *in, size_t in_len, 
{

	const unsigned char *ip = in;

	unsigned char *op = out;

	unsigned char *data_start;

	size_t l = in_len;

	size_t t = 0;

	signed char state_offset = -2;

	unsigned int m4_max_offset;



	// LZO v0 will never write 17 as first byte,

	// so this is used to version the bitstream

	// LZO v0 will never write 17 as first byte (except for zero-length

	// input), so this is used to version the bitstream

	if (bitstream_version > 0) {

		*op++ = 17;

		*op++ = bitstream_version;
@@ -306,6 +307,8 @@ int lzogeneric1x_1_compress(const unsigned char *in, size_t in_len, 
		m4_max_offset = M4_MAX_OFFSET_V0;

	}



	data_start = op;



	while (l > 20) {

		size_t ll = l <= (m4_max_offset + 1) ? l : (m4_max_offset + 1);

		uintptr_t ll_end = (uintptr_t) ip + ll;
@@ -324,7 +327,7 @@ int lzogeneric1x_1_compress(const unsigned char *in, size_t in_len, 
	if (t > 0) {

		const unsigned char *ii = in + in_len - t;



		if (op == out && t <= 238) {

		if (op == data_start && t <= 238) {

			*op++ = (17 + t);

		} else if (t <= 3) {

			op[state_offset] |= t;

lib/lzo/lzo1x_decompress_safe.c

+1 −3
Original line number Diff line number Diff line
@@ -54,11 +54,9 @@ int lzo1x_decompress_safe(const unsigned char *in, size_t in_len, 
	if (unlikely(in_len < 3))

		goto input_overrun;



	if (likely(*ip == 17)) {

	if (likely(in_len >= 5) && likely(*ip == 17)) {

		bitstream_version = ip[1];

		ip += 2;

		if (unlikely(in_len < 5))

			goto input_overrun;

	} else {

		bitstream_version = 0;

	}

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