From 04f052c56ded5ab6a904e3a264a73dc0412b2e78 Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Tue, 15 Jun 2021 15:07:57 +0200 Subject: unlzma: fix a case where we could read before beginning of buffer Testcase: 21 01 01 00 00 00 00 00 e7 01 01 01 ef 00 df b6 00 17 02 10 11 0f ff 00 16 00 00 Unfortunately, the bug is not reliably causing a segfault, the behavior depends on what's in memory before the buffer. function old new delta unpack_lzma_stream 2762 2768 +6 Signed-off-by: Denys Vlasenko --- archival/libarchive/decompress_unlzma.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'archival/libarchive') diff --git a/archival/libarchive/decompress_unlzma.c b/archival/libarchive/decompress_unlzma.c index 0744f23..fb5aac8 100644 --- a/archival/libarchive/decompress_unlzma.c +++ b/archival/libarchive/decompress_unlzma.c @@ -290,8 +290,11 @@ unpack_lzma_stream(transformer_state_t *xstate) uint32_t pos; pos = buffer_pos - rep0; - if ((int32_t)pos < 0) + if ((int32_t)pos < 0) { pos += header.dict_size; + if ((int32_t)pos < 0) + goto bad; + } match_byte = buffer[pos]; do { int bit; -- cgit v1.1