From fa1936405b6a84e5c9bb440912c23d532772f958 Mon Sep 17 00:00:00 2001 From: Robin Watts Date: Thu, 21 Jul 2016 15:39:11 +0100 Subject: Bug 696941: Fix use after free. The file is HORRIBLY corrupt, and triggers Sophos to think it's PDF malware (which it isn't). It does however trigger a use after free, worked around here. --- source/pdf/pdf-xref.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/source/pdf/pdf-xref.c b/source/pdf/pdf-xref.c index 576c315d..32225998 100644 --- a/source/pdf/pdf-xref.c +++ b/source/pdf/pdf-xref.c @@ -1184,8 +1184,14 @@ pdf_load_xref(fz_context *ctx, pdf_document *doc, pdf_lexbuf *buf) fz_throw(ctx, FZ_ERROR_GENERIC, "object offset out of range: %d (%d 0 R)", (int)entry->ofs, i); } if (entry->type == 'o') - if (entry->ofs <= 0 || entry->ofs >= xref_len || pdf_get_xref_entry(ctx, doc, entry->ofs)->type != 'n') - fz_throw(ctx, FZ_ERROR_GENERIC, "invalid reference to an objstm that does not exist: %d (%d 0 R)", (int)entry->ofs, i); + { + /* Read this into a local variable here, because pdf_get_xref_entry + * may solidify the xref, hence invalidating "entry", meaning we + * need a stashed value for the throw. */ + fz_off_t ofs = entry->ofs; + if (ofs <= 0 || ofs >= xref_len || pdf_get_xref_entry(ctx, doc, ofs)->type != 'n') + fz_throw(ctx, FZ_ERROR_GENERIC, "invalid reference to an objstm that does not exist: %d (%d 0 R)", (int)ofs, i); + } } } -- cgit v1.2.3