Passing $where predicate to db.currentOp() crashes mongod

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    • Type: Bug
    • Resolution: Done
    • Priority: Major - P3
    • 2.2.7, 2.4.9
    • Affects Version/s: 2.2.5, 2.4.5
    • Component/s: Admin
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    • ALL
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    • 3
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      Issue Status as of December 30th, 2013

      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:
0x10044c60b 0x100001121 0x1000013a2 0x7fff979285aa 0 0x10021a733 0x10021d43b 0x10021dcb9 0x10021e657 0x10021c14e 0x10021d619 0x10021dcb9 0x1002b472a 0x1002b2628 0x1002a7464 0x1002dbcf2 0x100240b14 0x1001ee10f 0x10000b682 0x100441fd9 
 0   mongod                              0x000000010044c60b _ZN5mongo15printStackTraceERSo + 43
 1   mongod                              0x0000000100001121 _ZN5mongo10abruptQuitEi + 225
 2   mongod                              0x00000001000013a2 _ZN5mongo24abruptQuitWithAddrSignalEiP9__siginfoPv + 242
 3   libsystem_platform.dylib            0x00007fff979285aa _sigtramp + 26
 4   ???                                 0x0000000000000000 0x0 + 0
 5   mongod                              0x000000010021a733 _ZN5mongo7Matcher10parseWhereERKNS_11BSONElementE + 
...

      SOLUTION
      Mongod now returns the following error message when $where is used in db.currentOp():

      no valid context found for $where

      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;}})
Fri Aug 16 04:45:35.459 trying reconnect to 127.0.0.1:27017

      Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffeb733700 (LWP 5112)]
mongo::Matcher::parseWhere (this=0x7ffff6b7a3c0, e=...) at src/mongo/db/matcher.cpp:432
warning: Source file is more recent than executable.
432	        _where = new Where( cc().ns() );
(gdb) bt
#0  mongo::Matcher::parseWhere (this=0x7ffff6b7a3c0, e=...) at src/mongo/db/matcher.cpp:432
#1  0x0000000000a47083 in mongo::Matcher::parseMatchExpressionElement (this=0x7ffff6b7a3c0, e=...,
    nested=false) at src/mongo/db/matcher.cpp:454
#2  0x0000000000a478c5 in mongo::Matcher::Matcher (this=0x7ffff6b7a3c0, jsobj=..., nested=false)
    at src/mongo/db/matcher.cpp:541
#3  0x00000000009f5aa8 in mongo::inProgCmd (m=..., dbresponse=...) at src/mongo/db/instance.cpp:170
#4  0x00000000009f82a1 in mongo::assembleResponse (m=..., dbresponse=..., remote=...)
    at src/mongo/db/instance.cpp:350
#5  0x00000000006e8b68 in mongo::MyMessageHandler::process (this=<optimized out>, m=...,
    port=0x7ffff6d00b80, le=0x7ffff6d01640) at src/mongo/db/db.cpp:194
#6  0x0000000000dc659e in mongo::PortMessageServer::handleIncomingMsg (arg=0x7ffff6a87ab0)
    at src/mongo/util/net/message_server_port.cpp:206
#7  0x00007ffff7bc4e9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#8  0x00007ffff6eda4bd in clone () from /lib/x86_64-linux-gnu/libc.so.6
#9  0x0000000000000000 in ?? ()
(gdb)

      Verified affects 2.2.5 and 2.4.5, and does not affect 2.0.9 and 2.5.1.

            Assignee:
            Matt Dannenberg (Inactive)
            Reporter:
            J Rassi (Inactive)
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              Created:
              Updated:
              Resolved: