From 112d963a0542b1280667e2eb2727a8946d9bcf8d Mon Sep 17 00:00:00 2001
From: Tobias Stoeckmann <stoeckmann@users.noreply.github.com>
Date: Mon, 13 Mar 2017 08:14:42 +0100
Subject: [PATCH] journal: prevent integer overflow while validating header
 (#5569)

It is possible to overflow uint64_t while validating the header of
a journal file. To prevent this, the addition itself is checked to
be within the limits of UINT64_MAX first.

To keep this readable, I have introduced two stack variables which
hold the converted values during validation.
(cherry picked from commit 6f94e420e8355421fc31713a0df760d6b20473ac)
---
 src/journal/journal-file.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/journal/journal-file.c b/src/journal/journal-file.c
index a6ccb67..14cb01a 100644
--- a/src/journal/journal-file.c
+++ b/src/journal/journal-file.c
@@ -546,6 +546,8 @@ static bool warn_wrong_flags(const JournalFile *f, bool compatible) {
 }
 
 static int journal_file_verify_header(JournalFile *f) {
+        uint64_t arena_size, header_size;
+
         assert(f);
         assert(f->header);
 
@@ -564,17 +566,21 @@ static int journal_file_verify_header(JournalFile *f) {
         if (f->header->state >= _STATE_MAX)
                 return -EBADMSG;
 
+        header_size = le64toh(f->header->header_size);
+
         /* The first addition was n_data, so check that we are at least this large */
-        if (le64toh(f->header->header_size) < HEADER_SIZE_MIN)
+        if (header_size < HEADER_SIZE_MIN)
                 return -EBADMSG;
 
         if (JOURNAL_HEADER_SEALED(f->header) && !JOURNAL_HEADER_CONTAINS(f->header, n_entry_arrays))
                 return -EBADMSG;
 
-        if ((le64toh(f->header->header_size) + le64toh(f->header->arena_size)) > (uint64_t) f->last_stat.st_size)
+        arena_size = le64toh(f->header->arena_size);
+
+        if (UINT64_MAX - header_size < arena_size || header_size + arena_size > (uint64_t) f->last_stat.st_size)
                 return -ENODATA;
 
-        if (le64toh(f->header->tail_object_offset) > (le64toh(f->header->header_size) + le64toh(f->header->arena_size)))
+        if (le64toh(f->header->tail_object_offset) > header_size + arena_size)
                 return -ENODATA;
 
         if (!VALID64(le64toh(f->header->data_hash_table_offset)) ||
-- 
2.9.3