[CASSANDRA-4111] Serializing cache can cause Segfault in 1.1

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 1.1.0
• Severity: Normal
• Assignee: Vijay
• Reporter: Vijay

Authors

Vijay

Reviewers

Jonathan Ellis

• Created: 02/Apr/12 23:29
• Updated: 16/Apr/19 09:32
• Resolved: 03/Apr/12 19:35

Description

Rare but this can happen per sure, looks like this issue is after CASSANDRA-3862 hence affectes only 1.1

FreeableMemory old = map.get(key);
if (old == null)
return false;

// see if the old value matches the one we want to replace
FreeableMemory mem = serialize(value);
if (mem == null)
return false; // out of memory. never mind.
V oldValue = deserialize(old);
boolean success = oldValue.equals(oldToReplace) && map.replace(key, old, mem);

if (success)
old.unreference();
else
mem.unreference();
return success;

in the above code block we deserialize(old) without taking reference to the old memory, this can case seg faults when the old is reclaimed (free is called)
Fix is to get the reference just for deserialization

V oldValue;
// reference old guy before de-serializing
old.reference();
try

{ oldValue = deserialize(old); }

finally

{ old.unreference(); }