net: make sockptr_is_null strict aliasing safe

Christoph Hellwig · davem330 · commit 035bfd051eae · 2020-07-28T13:43:40.000-07:00
While the kernel in general is not strict aliasing safe we can trivially
do that in sockptr_is_null without affecting code generation, so always
check the actually assigned union member.

Reported-by: Jan Engelhardt &lt;jengelh@inai.de&gt;
Signed-off-by: Christoph Hellwig &lt;hch@lst.de&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
diff --git a/include/linux/sockptr.h b/include/linux/sockptr.h
@@ -64,7 +64,9 @@ static inline int __must_check init_user_sockptr(sockptr_t *sp, void __user *p)
 
 static inline bool sockptr_is_null(sockptr_t sockptr)
 {
-	return !sockptr.user && !sockptr.kernel;
+	if (sockptr_is_kernel(sockptr))
+		return !sockptr.kernel;
+	return !sockptr.user;
 }
 
 static inline int copy_from_sockptr(void *dst, sockptr_t src, size_t size)

Original file line number	Diff line number	Diff line change
`@@ -64,7 +64,9 @@ static inline int __must_check init_user_sockptr(sockptr_t sp, void __user p)`
`64`	`64`
`65`	`65`	`static inline bool sockptr_is_null(sockptr_t sockptr)`
`66`	`66`	`{`
`67`		`- return !sockptr.user && !sockptr.kernel;`
	`67`	`+ if (sockptr_is_kernel(sockptr))`
	`68`	`+ return !sockptr.kernel;`
	`69`	`+ return !sockptr.user;`
`68`	`70`	`}`
`69`	`71`
`70`	`72`	`static inline int copy_from_sockptr(void *dst, sockptr_t src, size_t size)`