From: Dave Rodgman <dave.rodgman@xxxxxxx> Subject: 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@xxxxxxx Signed-off-by: Dave Rodgman <dave.rodgman@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/lzo.txt | 8 +++++--- lib/lzo/lzo1x_compress.c | 9 ++++++--- lib/lzo/lzo1x_decompress_safe.c | 4 +--- 3 files changed, 12 insertions(+), 9 deletions(-) --- a/Documentation/lzo.txt~lib-lzo-fix-bugs-for-very-short-or-empty-input +++ a/Documentation/lzo.txt @@ -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 ] --- a/lib/lzo/lzo1x_compress.c~lib-lzo-fix-bugs-for-very-short-or-empty-input +++ a/lib/lzo/lzo1x_compress.c @@ -291,13 +291,14 @@ int lzogeneric1x_1_compress(const unsign { 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 unsign 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 unsign 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; --- a/lib/lzo/lzo1x_decompress_safe.c~lib-lzo-fix-bugs-for-very-short-or-empty-input +++ a/lib/lzo/lzo1x_decompress_safe.c @@ -54,11 +54,9 @@ int lzo1x_decompress_safe(const unsigned 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; } _
