slice bounds out of range in tree.go

[boindil]

Description

I stumbled upon this problem where gin seems trying to extend the slice further than the capacity allows.

I am unsure of the actual reason since my route looks pretty simple and its actually only affecting one of the routes (the others work fine).

The error only occurs, when the route is accessed.

2021/08/11 11:04:37 http: panic serving 10.42.28.200:59776: runtime error: slice bounds out of range [:4] with capacity 3
goroutine 241 [running]:
net/http.(*conn).serve.func1(0xc000366280)
	/usr/lib/go-1.15/src/net/http/server.go:1801 +0x147
panic(0xd26e60, 0xc0015d6be0)
	/usr/lib/go-1.15/src/runtime/panic.go:975 +0x47a
github.com/gin-gonic/gin.(*node).getValue(0xc0001ca380, 0xc00004b140, 0xa, 0xc0015da900, 0x486200, 0x0, 0x0, 0x0, 0xc0015da900, 0x0, ...)
	/build/myservice-0.0.0/obj-x86_64-linux-gnu/pkg/mod/github.com/gin-gonic/gin@v1.7.3/tree.go:481 +0xc65
github.com/gin-gonic/gin.(*Engine).handleHTTPRequest(0xc0003c5520, 0xc0015aa700)
	/build/myservice-0.0.0/obj-x86_64-linux-gnu/pkg/mod/github.com/gin-gonic/gin@v1.7.3/gin.go:482 +0x1b3
github.com/gin-gonic/gin.(*Engine).ServeHTTP(0xc0003c5520, 0xea7360, 0xc0015ae8c0, 0xc0001e8c00)
	/build/myservice-0.0.0/obj-x86_64-linux-gnu/pkg/mod/github.com/gin-gonic/gin@v1.7.3/gin.go:445 +0x15c
net/http.serverHandler.ServeHTTP(0xc0000f41c0, 0xea7360, 0xc0015ae8c0, 0xc0001e8c00)
	/usr/lib/go-1.15/src/net/http/server.go:2843 +0xa3
net/http.(*conn).serve(0xc000366280, 0xeaf2a0, 0xc0000fef80)
	/usr/lib/go-1.15/src/net/http/server.go:1925 +0x8ad
created by net/http.(*Server).Serve
	/usr/lib/go-1.15/src/net/http/server.go:2969 +0x36c

How to reproduce

unsure, route is called as following: "/servicename/api/v1/:paramname/myresource/:paramname2"

minimal example as to how the routes are built

	routes := router.Group("/servicename")
	privRoutes := routes.Group("/api/v1")
	privRoutesMyResource := privRoutes.Group("/:paramname/myresource")
	privRoutesMyResource .GET("/:paramname2", getResource)

Expectations

No error

Actual result

runrime error

Environment

• go version: Go 1.15.9
• gin version (or commit ref): 1.7.3
• operating system: debian/sid

[jimbirthday]

@boindil
I'm sorry I can't reproduce your mistake, can you give a more detailed code or use case?

func main() {
	router := gin.Default()
	routes := router.Group("/servicename")
	privRoutes := routes.Group("/api/v1")
	privRoutesMyResource := privRoutes.Group("/:paramname/myresource")
	privRoutesMyResource.GET("/:paramname2", getResource)
	router.Run(":8080")
}

func getResource(c *gin.Context) {
	c.JSON(200, gin.H{
		"dada": "ok",
	})
}

As you can see, I did not appear abnormal

[git-hulk]

Should be the same problem with this PR: #2820

[boindil]

@jimbirthday @git-hulk would make sense. I probably have a typo in one of my calling services which would be the reason for it only affecting this one route and me not being able to reproduce this right.

Good find, thanks @git-hulk !

[appleboy]

@boindil OK. I closed the issue.