From 975620255015aa7611fb2d9fbd539de60df4be73 Mon Sep 17 00:00:00 2001 From: Kou Wenqi Date: Fri, 15 Jul 2022 09:46:33 +0800 Subject: [PATCH] gif: Fix LZW decoder accepting invalid LZW code. The code value after a reset wasn't being validated, which means we would accept invalid codes. This could cause an infinite loop in the decoder. Fixes CVE-2020-29385 Fixes https://gitlab.gnome.org/GNOME/gdk-pixbuf/-/issues/164 --- gdk-pixbuf/lzw.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/gdk-pixbuf/lzw.c b/gdk-pixbuf/lzw.c index 9e052a6..105daf2 100644 --- a/gdk-pixbuf/lzw.c +++ b/gdk-pixbuf/lzw.c @@ -195,19 +195,20 @@ lzw_decoder_feed (LZWDecoder *self, if (self->last_code != self->clear_code && self->code_table_size < MAX_CODES) { if (self->code < self->code_table_size) add_code (self, self->code); - else if (self->code == self->code_table_size) + else add_code (self, self->last_code); - else { - /* Invalid code received - just stop here */ - self->last_code = self->eoi_code; - return output_length; - } /* When table is full increase code size */ if (self->code_table_size == (1 << self->code_size) && self->code_size < LZW_CODE_MAX) self->code_size++; } + /* Invalid code received - just stop here */ + if (self->code >= self->code_table_size) { + self->last_code = self->eoi_code; + return output_length; + } + /* Convert codeword into indexes */ n_written += write_indexes (self, output + n_written, output_length - n_written); } -- 2.33.0