got panic with RWMutex on 1.6.0 version

[congtranminh]

• With issues:

Description

After upgrade to 1.6.0, I got panic when use Get Set context.

panic: runtime error: invalid memory address or nil pointer dereference [recovered]
 	panic: runtime error: invalid memory address or nil pointer dereference
 [signal SIGSEGV: segmentation violation code=0x1 addr=0x10 pc=0x9193c3]
 goroutine 9 [running]:
 testing.tRunner.func1(0xc000137100)
 	/usr/local/go/src/testing/testing.go:830 +0x392
 panic(0xb33d40, 0x120e870)
 	/usr/local/go/src/runtime/panic.go:522 +0x1b5
 sync.(*RWMutex).RLock(...)
 	/usr/local/go/src/sync/rwmutex.go:48
 github.com/gin-gonic/gin.(*Context).Get(0xc0003b8000, 0xbfc6f8, 0x5, 0x2, 0x2, 0x10)
 	/go/pkg/mod/github.com/gin-gonic/gin@v1.6.1/context.go:239 +0x33

I compare with the 1.5.0 version, and saw that you used RWMutex inside the Get context function.
Please check and remove it as 1.5.0 version.

// Get returns the value for the given key, ie: (value, true).
// If the value does not exists it returns (nil, false)
func (c *Context) Get(key string) (value interface{}, exists bool) {
	c.KeysMutex.RLock()
	value, exists = c.Keys[key]
	c.KeysMutex.RUnlock()
	return
}

How to reproduce

Here my code example

type logger struct {
	GinCtx  *gin.Context
}

func (_this *logger) Set(key string, value interface{}) {
	if _this.GinCtx != nil {
		_this.GinCtx.Set(key, value)
	}
}

func (_this *logger) Get(key string) interface{} {
	if _this.GinCtx != nil {
		value, _ := _this.GinCtx.Get(key)
		return value
	}
	return nil
}

on handler package, I call this Get, Set function and got panic :(

Environment

• go version: 1.13
• gin version (or commit ref): 1.6.0, 1.6.1
• operating system: linux

[jdolitsky]

Same issue here using Gin 1.6.1, Go 1.14.1, Mac OS. Downgrading to Gin 1.5.0 fixes the issue.

[appleboy]

cc @AcoNCodes ref: #1391

[appleboy]

fix in #2305 please help to confirm PR.

[jdolitsky]

@appleboy - confirmed. Fixes things on my end.

[appleboy]

Also add unit testing:

func TestContextWithKeysMutex(t *testing.T) {
	c := &gin.Context{}
	c.Set("foo", "bar")

	value, err := c.Get("foo")
	assert.Equal(t, "bar", value)
	assert.True(t, err)

	value, err = c.Get("foo2")
	assert.Nil(t, value)
	assert.False(t, err)
}

@thinkerou Please help to review PR.

[appleboy]

bump to v1.6.2 https://github.com/gin-gonic/gin/releases/tag/v1.6.2

[congtranminh]

thank you guys.