Gitea: compare: index out of range panic on master and v1.11

[silverwind]

• Gitea version (or commit ref): https://github.com/go-gitea/gitea/commit/cc2916dc5acea2c32372082986f8c2e2c43e55fe
• Git version: 2.22.0
• Operating system: Linux
• Database (use [x]):
  
  
  
  • [ ] PostgreSQL
  
  
  • [x] MySQL
  
  
  • [ ] MSSQL
  
  
  • [ ] SQLite
  
  
• Can you reproduce the bug at https://try.gitea.io:
  
  
  
  • [ ] Yes (provide example URL)
  
  
  • [ ] No
  
  
  • [x] Not relevant
  
  

Description

Panic when opening a page compare/master...branch. Stack looks similar to https://github.com/go-gitea/gitea/issues/9173 and https://github.com/go-gitea/gitea/issues/9217 but https://github.com/go-gitea/gitea/pull/9187 did not fix it. I can reproduce on both master and v1.11 release branch. I can't share the diff, but may be able to answer questions about it.

````
2020/01/17 02:12:33 ...les/context/panic.go:35:1() [E] PANIC:: runtime error: index out of range [-1]
/usr/lib/golang/src/runtime/panic.go:75 (0x42f8b2)
goPanicIndex: panic(boundsError{x: int64(x), signed: true, y: y, code: boundsIndex})
gitea/services/gitdiff/gitdiff.go:358 (0x12fdf83)
gitea/services/gitdiff/gitdiff.go:870 (0x1301c74)
gitea/services/gitdiff/gitdiff.go:811 (0x1404a2f)
gitea/routers/repo/compare.go:282 (0x1404984)
gitea/routers/repo/compare.go:387 (0x1405f33)
/usr/lib/golang/src/reflect/value.go:460 (0x491b15)
Value.call: call(frametype, fn, args, uint32(frametype.size), uint32(retOffset))
/usr/lib/golang/src/reflect/value.go:321 (0x4912d3)
Value.Call: return v.call("Call", in)
gitea/vendor/gitea.com/macaron/inject/inject.go:177 (0x9b0ef9)
gitea/vendor/gitea.com/macaron/inject/inject.go:137 (0x9b08a9)
gitea/vendor/gitea.com/macaron/macaron/context.go:121 (0x9e1a78)
gitea/vendor/gitea.com/macaron/macaron/context.go:112 (0xfc8f01)
gitea/modules/context/repo.go:576 (0xfc8eea)
/usr/lib/golang/src/reflect/value.go:460 (0x491b15)
Value.call: call(frametype, fn, args, uint32(frametype.size), uint32(retOffset))
/usr/lib/golang/src/reflect/value.go:321 (0x4912d3)
Value.Call: return v.call("Call", in)
gitea/vendor/gitea.com/macaron/inject/inject.go:177 (0x9b0ef9)
gitea/vendor/gitea.com/macaron/inject/inject.go:137 (0x9b08a9)
gitea/vendor/gitea.com/macaron/macaron/context.go:121 (0x9e1a78)
gitea/vendor/gitea.com/macaron/macaron/context.go:112 (0xfc68f1)
gitea/modules/context/panic.go:39 (0xfc68dd)
/usr/lib/golang/src/reflect/value.go:460 (0x491b15)
Value.call: call(frametype, fn, args, uint32(frametype.size), uint32(retOffset))
/usr/lib/golang/src/reflect/value.go:321 (0x4912d3)
Value.Call: return v.call("Call", in)
gitea/vendor/gitea.com/macaron/inject/inject.go:177 (0x9b0ef9)
gitea/vendor/gitea.com/macaron/inject/inject.go:137 (0x9b08a9)
gitea/vendor/gitea.com/macaron/macaron/context.go:121 (0x9e1a78)
gitea/vendor/gitea.com/macaron/macaron/context.go:112 (0xa79cd5)

!/bin/bash

gitea/vendor/gitea.com/macaron/session/session.go:192 (0xa79cc0)
gitea/vendor/gitea.com/macaron/macaron/context.go:79 (0x9e1920)
gitea/vendor/gitea.com/macaron/inject/inject.go:157 (0x9b0c09)
gitea/vendor/gitea.com/macaron/inject/inject.go:135 (0x9b0998)
gitea/vendor/gitea.com/macaron/macaron/context.go:121 (0x9e1a78)
gitea/vendor/gitea.com/macaron/macaron/context.go:112 (0x9f3059)
gitea/vendor/gitea.com/macaron/macaron/recovery.go:161 (0x9f3047)
gitea/vendor/gitea.com/macaron/macaron/logger.go:40 (0x9e55f3)
gitea/vendor/gitea.com/macaron/inject/inject.go:157 (0x9b0c09)
gitea/vendor/gitea.com/macaron/inject/inject.go:135 (0x9b0998)
gitea/vendor/gitea.com/macaron/macaron/context.go:121 (0x9e1a78)
gitea/vendor/gitea.com/macaron/macaron/context.go:112 (0x9f2390)
gitea/vendor/gitea.com/macaron/macaron/logger.go:52 (0x9f237b)
gitea/vendor/gitea.com/macaron/macaron/logger.go:40 (0x9e55f3)
gitea/vendor/gitea.com/macaron/inject/inject.go:157 (0x9b0c09)
gitea/vendor/gitea.com/macaron/inject/inject.go:135 (0x9b0998)
gitea/vendor/gitea.com/macaron/macaron/context.go:121 (0x9e1a78)
gitea/vendor/gitea.com/macaron/macaron/router.go:187 (0x9f4276)
gitea/vendor/gitea.com/macaron/macaron/router.go:303 (0x9edc55)
gitea/vendor/gitea.com/macaron/macaron/macaron.go:218 (0x9e698a)
gitea/vendor/github.com/gorilla/context/context.go:141 (0xd1846d)
/usr/lib/golang/src/net/http/server.go:2007 (0x751bc3)
HandlerFunc.ServeHTTP: f(w, r)
/usr/lib/golang/src/net/http/server.go:2802 (0x755013)
serverHandler.ServeHTTP: handler.ServeHTTP(rw, req)
/usr/lib/golang/src/net/http/server.go:1890 (0x7509b4)
(*conn).serve: serverHandler{c.server}.ServeHTTP(w, w.req)
/usr/lib/golang/src/runtime/asm_amd64.s:1357 (0x461150)
goexit: BYTE $0x90 // NOP
````

[lafriks]

Could it be that #9808 fixed this?

[silverwind]

@lunny is it related?

[lunny]

@silverwind Maybe. I just review the code and found that. Since #9808 merged, could you confirm that? I will send back port to v1.11 and v1.10

[silverwind]

Unfortunately, no, it does not fix it. Updated stacktrace which is now for https://github.com/go-gitea/gitea/commit/cc2916dc5acea2c32372082986f8c2e2c43e55fe.

[lunny]

So there is a file has changes but there is no any section. @silverwind Could you paste that patch?

[silverwind]

Afraid I can not share the private patch data, I'll check it out myself later.

[silverwind]

@lunny It can be reproduced with a simple file mode change:

https://try.gitea.io/silverwind/symlink-test/compare/master...mode

```` diff
$ git diff master mode
diff --git a/file b/file
old mode 100644
new mode 100755