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POCrashing MongoDB with one badly named field, what's so special about it?
 

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  1. POCrashing MongoDB with one badly named field, what's so special about it?
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    <p>Using the Java driver, we today discovered that is possible to bring a MongoDB instance down with a segmentation fault. </p> <pre><code>new Mongo().getDB("test").getCollection("test"). insert(new BasicDBObject("\u0000Žö", "")); </code></pre> <p>This will produce the following output from <code>mongod</code> before it dies:</p> <pre><code>Fri Nov 16 18:53:18 Invalid access at address: 0xbac3c5fe from thread: conn5 Fri Nov 16 18:53:18 Got signal: 11 (Segmentation fault: 11). Fri Nov 16 18:53:18 Backtrace: 0x10004241b 0x10005628b 0x100056941 0x7fff828afcfa 0x1 0x100281611 0x100288c91 0x10006c501 0x10058e50c 0x1005e31d3 0x7fff8285b8bf 0x7fff8285eb75 0 mongod 0x000000010004241b _ZN5mongo15printStackTraceERSo + 43 1 mongod 0x000000010005628b _ZN5mongo10abruptQuitEi + 987 2 mongod 0x0000000100056941 _ZN5mongo24abruptQuitWithAddrSignalEiP9__siginfoPv + 673 3 libsystem_c.dylib 0x00007fff828afcfa _sigtramp + 26 4 ??? 0x0000000000000001 0x0 + 1 5 mongod 0x0000000100281611 _ZN5mongo14receivedInsertERNS_7MessageERNS_5CurOpE + 1841 6 mongod 0x0000000100288c91 _ZN5mongo16assembleResponseERNS_7MessageERNS_10DbResponseERKNS_11HostAndPortE + 4705 7 mongod 0x000000010006c501 _ZN5mongo16MyMessageHandler7processERNS_7MessageEPNS_21AbstractMessagingPortEPNS_9LastErrorE + 257 8 mongod 0x000000010058e50c _ZN5mongo3pms9threadRunEPNS_13MessagingPortE + 1084 9 mongod 0x00000001005e31d3 thread_proxy + 163 10 libsystem_c.dylib 0x00007fff8285b8bf _pthread_start + 335 11 libsystem_c.dylib 0x00007fff8285eb75 thread_start + 13 </code></pre> <p>I've been trying to understand what on earth makes this magical field name special. Removing <strong>any</strong> of the characters involved makes mongodb survive just fine, and the stack trace isn't making me any wiser.</p> <p>I've written up a short <a href="http://jwdev.tumblr.com/post/35851221681/how-to-crash-mongodb-in-1-line-of-java" rel="nofollow">blog post</a> on the issue, and filed a <a href="https://jira.mongodb.org/browse/SERVER-7691" rel="nofollow">JIRA ticket</a> at mongodb.org, but my curiosity is killing me. Can anyone figure out what makes <code>\u0000Žö</code> special?</p> <p><strong>Edit to clarify</strong>: <code>\u0000</code> and <code>\u0000Ž</code> is fine, and so is <code>\u0000Žsomerandomtext</code> </p>
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    1. COIs this bug resolved by the lastest mongo java driver 2.10.1? I tested and find without the --objcheck turned on, the db server will still crash.
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