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This patch came from https://git.ghostscript.com/?p=mupdf.git;a=patch;h=cee7cefc610d42fd383b3c80c12cbc675443176a
and fixes CVE-2021-3407.
From cee7cefc610d42fd383b3c80c12cbc675443176a Mon Sep 17 00:00:00 2001
From: Robin Watts <Robin.Watts@artifex.com>
Date: Fri, 22 Jan 2021 17:05:15 +0000
Subject: [PATCH] Bug 703366: Fix double free of object during linearization.
This appears to happen because we parse an illegal object from
a broken file and assign it to object 0, which is defined to
be free.
Here, we fix the parsing code so this can't happen.
---
source/pdf/pdf-parse.c | 6 ++++++
source/pdf/pdf-xref.c | 2 ++
2 files changed, 8 insertions(+)
diff --git a/source/pdf/pdf-parse.c b/source/pdf/pdf-parse.c
index 7abc8c3d4..5761c3351 100644
--- a/source/pdf/pdf-parse.c
+++ b/source/pdf/pdf-parse.c
@@ -749,6 +749,12 @@ pdf_parse_ind_obj(fz_context *ctx, pdf_document *doc,
fz_throw(ctx, FZ_ERROR_SYNTAX, "expected generation number (%d ? obj)", num);
}
gen = buf->i;
+ if (gen < 0 || gen >= 65536)
+ {
+ if (try_repair)
+ *try_repair = 1;
+ fz_throw(ctx, FZ_ERROR_SYNTAX, "invalid generation number (%d)", gen);
+ }
tok = pdf_lex(ctx, file, buf);
if (tok != PDF_TOK_OBJ)
diff --git a/source/pdf/pdf-xref.c b/source/pdf/pdf-xref.c
index 1b2bdcd59..30197b4b8 100644
--- a/source/pdf/pdf-xref.c
+++ b/source/pdf/pdf-xref.c
@@ -1190,6 +1190,8 @@ pdf_read_new_xref(fz_context *ctx, pdf_document *doc, pdf_lexbuf *buf)
{
ofs = fz_tell(ctx, doc->file);
trailer = pdf_parse_ind_obj(ctx, doc, doc->file, buf, &num, &gen, &stm_ofs, NULL);
+ if (num == 0)
+ fz_throw(ctx, FZ_ERROR_GENERIC, "Trailer object number cannot be 0\n");
}
fz_catch(ctx)
{
--
2.17.1
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