Details
Description
ISSUE SUMMARY
$where can cause a segfault when used in db.currentOp()
USER IMPACT
Mongod will crash with a stack trace showing an error in the mongo::Matcher::parseWhere method, similar to the following
Fri Nov 15 19:34:35.259 Backtrace:
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0x10044c60b 0x100001121 0x1000013a2 0x7fff979285aa 0 0x10021a733 0x10021d43b 0x10021dcb9 0x10021e657 0x10021c14e 0x10021d619 0x10021dcb9 0x1002b472a 0x1002b2628 0x1002a7464 0x1002dbcf2 0x100240b14 0x1001ee10f 0x10000b682 0x100441fd9
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0 mongod 0x000000010044c60b _ZN5mongo15printStackTraceERSo + 43
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1 mongod 0x0000000100001121 _ZN5mongo10abruptQuitEi + 225
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2 mongod 0x00000001000013a2 _ZN5mongo24abruptQuitWithAddrSignalEiP9__siginfoPv + 242
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3 libsystem_platform.dylib 0x00007fff979285aa _sigtramp + 26
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4 ??? 0x0000000000000000 0x0 + 0
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5 mongod 0x000000010021a733 _ZN5mongo7Matcher10parseWhereERKNS_11BSONElementE +
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...
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SOLUTION
Mongod now returns the following error message when $where is used in db.currentOp():
no valid context found for $where
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WORKAROUNDS
Users should avoid using $where in db.currentOp()
PATCHES
Production release v2.4.9 and v2.2.7 contain the fix for this issue, and production release v2.6.0 will have a brand new query engine, which does not contain this bug.
Using a $where predicate with db.currentOp() on mongod causes a null dereference. Matcher::parseWhere() accesses the current context to look up which namespace to pass to the Where constructor, but cc()->_context is null, since db.currentOp() never sets a context.
> db.currentOp({$where:function(){return true;}})
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Fri Aug 16 04:45:35.459 trying reconnect to 127.0.0.1:27017
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Program received signal SIGSEGV, Segmentation fault.
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[Switching to Thread 0x7fffeb733700 (LWP 5112)]
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mongo::Matcher::parseWhere (this=0x7ffff6b7a3c0, e=...) at src/mongo/db/matcher.cpp:432
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warning: Source file is more recent than executable.
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432 _where = new Where( cc().ns() );
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(gdb) bt
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#0 mongo::Matcher::parseWhere (this=0x7ffff6b7a3c0, e=...) at src/mongo/db/matcher.cpp:432
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#1 0x0000000000a47083 in mongo::Matcher::parseMatchExpressionElement (this=0x7ffff6b7a3c0, e=...,
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nested=false) at src/mongo/db/matcher.cpp:454
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#2 0x0000000000a478c5 in mongo::Matcher::Matcher (this=0x7ffff6b7a3c0, jsobj=..., nested=false)
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at src/mongo/db/matcher.cpp:541
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#3 0x00000000009f5aa8 in mongo::inProgCmd (m=..., dbresponse=...) at src/mongo/db/instance.cpp:170
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#4 0x00000000009f82a1 in mongo::assembleResponse (m=..., dbresponse=..., remote=...)
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at src/mongo/db/instance.cpp:350
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#5 0x00000000006e8b68 in mongo::MyMessageHandler::process (this=<optimized out>, m=...,
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port=0x7ffff6d00b80, le=0x7ffff6d01640) at src/mongo/db/db.cpp:194
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#6 0x0000000000dc659e in mongo::PortMessageServer::handleIncomingMsg (arg=0x7ffff6a87ab0)
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at src/mongo/util/net/message_server_port.cpp:206
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#7 0x00007ffff7bc4e9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
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#8 0x00007ffff6eda4bd in clone () from /lib/x86_64-linux-gnu/libc.so.6
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#9 0x0000000000000000 in ?? ()
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(gdb)
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Verified affects 2.2.5 and 2.4.5, and does not affect 2.0.9 and 2.5.1.
Attachments
Issue Links
- is duplicated by
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SERVER-12003 MongoDB server crushes when db.$cmd.sys.inprog is accessed from shell
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- Closed
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- is related to
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- Closed
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