From: Myoungwon Oh <myoungwon.oh@samsung.com>
Date: Thu, 31 Aug 2023 02:43:24 +0000 (+0900)
Subject: crimson/os/seastore/cbj: fix a potential overflow bug
X-Git-Tag: v19.0.0~463^2
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=36982b66574ff277e04a02d5b9a28e80d0790778;p=ceph.git

crimson/os/seastore/cbj: fix a potential overflow bug

CircularBoundedJournal is similar to circular queue, so segment_seq
increases after rolling. However, current implementation always
increases segment_seq_t when rolling occurs, resulting in
the overflow if segment_seq_t hits MAX_SEG_SEQ.

To mitigate this, this commit changes the type of the segment_seq_t
to uint64_t.

Signed-off-by: Myoungwon Oh <myoungwon.oh@samsung.com>
---

diff --git a/src/crimson/os/seastore/journal/circular_journal_space.cc b/src/crimson/os/seastore/journal/circular_journal_space.cc
index c36064acb12..123bb91353c 100644
--- a/src/crimson/os/seastore/journal/circular_journal_space.cc
+++ b/src/crimson/os/seastore/journal/circular_journal_space.cc
@@ -42,8 +42,10 @@ CircularJournalSpace::roll_ertr::future<> CircularJournalSpace::roll() {
     get_records_start(),
     get_device_id());
   auto seq = get_written_to();
+  seq.segment_seq++;
+  assert(seq.segment_seq < MAX_SEG_SEQ);
   set_written_to(
-    journal_seq_t{++seq.segment_seq, paddr});
+    journal_seq_t{seq.segment_seq, paddr});
   return roll_ertr::now();
 }
 
diff --git a/src/crimson/os/seastore/seastore_types.h b/src/crimson/os/seastore/seastore_types.h
index 26c5017aadb..0b4ad853687 100644
--- a/src/crimson/os/seastore/seastore_types.h
+++ b/src/crimson/os/seastore/seastore_types.h
@@ -210,7 +210,7 @@ constexpr segment_id_t NULL_SEG_ID = MAX_SEG_ID;
 
 /* Monotonically increasing segment seq, uniquely identifies
  * the incarnation of a segment */
-using segment_seq_t = uint32_t;
+using segment_seq_t = uint64_t;
 static constexpr segment_seq_t MAX_SEG_SEQ =
   std::numeric_limits<segment_seq_t>::max();
 static constexpr segment_seq_t NULL_SEG_SEQ = MAX_SEG_SEQ;