Major Description
While debugging an issue with cbbackupmgr (MB-37869) I managed to get a segmentation fault while canceling a set with meta operation. Below I've provided the stack trace which shows that I got a nil pointer dereference on the mutex lock. For me to call 'Cancel' on the operation it mustn't have been nil at the time (in backup).
panic: runtime error: invalid memory address or nil pointer dereference
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[signal SIGSEGV: segmentation violation code=0x1 addr=0xbc pc=0x78306d]
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goroutine 82 [running]:
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sync.(*Mutex).Lock(...)
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/usr/lib/go/src/sync/mutex.go:74
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github.com/couchbase/gocbcore%2ev8.(*memdQRequest).Cancel(0x0, 0xc000269dd0)
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/home/james/Projects/couchbase-build/godeps/src/github.com/couchbase/gocbcore.v8/memdqpackets.go:103 +0x2d
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github.com/couchbase/backup/couchbase.(*operation).complete(0xc00066c780, 0x0, 0x0)
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/home/james/Projects/couchbase-build/goproj/src/github.com/couchbase/backup/couchbase/operation.go:113 +0xca
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github.com/couchbase/backup/couchbase.(*SetWithMeta).callback(...)
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/home/james/Projects/couchbase-build/goproj/src/github.com/couchbase/backup/couchbase/operation.go:240
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github.com/couchbase/gocbcore%2ev8.(*Agent).SetMetaEx.func1(0xc00053d0e0, 0xc00066c870, 0x0, 0x0)
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/home/james/Projects/couchbase-build/godeps/src/github.com/couchbase/gocbcore.v8/agentops_internal.go:121 +0xd7
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github.com/couchbase/gocbcore%2ev8.(*memdQRequest).tryCallback(0xc00066c870, 0xc00053d0e0, 0x0, 0x0, 0xc0005616a0)
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/home/james/Projects/couchbase-build/godeps/src/github.com/couchbase/gocbcore.v8/memdqpackets.go:90 +0xbc
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github.com/couchbase/gocbcore%2ev8.(*memdClient).resolveRequest(0xc0000b5220, 0xc00053d0e0)
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/home/james/Projects/couchbase-build/godeps/src/github.com/couchbase/gocbcore.v8/memdclient.go:241 +0x2ae
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github.com/couchbase/gocbcore%2ev8.(*memdClient).run.func2(0xc0000b5220, 0xc00002c840, 0xc00002c900, 0xc00002c960)
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/home/james/Projects/couchbase-build/godeps/src/github.com/couchbase/gocbcore.v8/memdclient.go:345 +0x295
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created by github.com/couchbase/gocbcore%2ev8.(*memdClient).run
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/home/james/Projects/couchbase-build/godeps/src/github.com/couchbase/gocbcore.v8/memdclient.go:272 +0x105
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Expected results:
If a user calls 'Cancel' on an inflight operation (at the time a non nil pointer) it should return whether or not the operation succeeds (e.g. it shouldn't panic).
Actual results:
Got a nil pointer dereference when trying to aquire exclusive access to the 'memdQRequest'
Version:
gocbcore.v8 - '63dd10dcba15d5d9253774df778d36635c337b67'
I understand that this is a slightly older version of gocbcore, however, I've look at the code in master (although in a different location) it appears that this panic would still be possible.