x86/uaccess: Add ENDBR to __put_user_nocheck*()

The __put_user_nocheck*() inner labels are exported, so in keeping with
the "allow exported functions to be indirectly called" policy, add
ENDBR.

Fixes: ed53a0d ("x86/alternative: Use .ibt_endbr_seal to seal indirect calls")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/207f02177a23031091d1a608de6049a9e5e8ff80.1650300597.git.jpoimboe@redhat.com

Author: jpoimboe

arch/x86/lib/putuser.S

@@ -48,6 +48,7 @@ SYM_FUNC_START(__put_user_1)
 	cmp %_ASM_BX,%_ASM_CX
 	jae .Lbad_put_user
 SYM_INNER_LABEL(__put_user_nocheck_1, SYM_L_GLOBAL)
+	ENDBR
 	ASM_STAC
 1:	movb %al,(%_ASM_CX)
 	xor %ecx,%ecx
@@ -62,6 +63,7 @@ SYM_FUNC_START(__put_user_2)
 	cmp %_ASM_BX,%_ASM_CX
 	jae .Lbad_put_user
 SYM_INNER_LABEL(__put_user_nocheck_2, SYM_L_GLOBAL)
+	ENDBR
 	ASM_STAC
 2:	movw %ax,(%_ASM_CX)
 	xor %ecx,%ecx
@@ -76,6 +78,7 @@ SYM_FUNC_START(__put_user_4)
 	cmp %_ASM_BX,%_ASM_CX
 	jae .Lbad_put_user
 SYM_INNER_LABEL(__put_user_nocheck_4, SYM_L_GLOBAL)
+	ENDBR
 	ASM_STAC
 3:	movl %eax,(%_ASM_CX)
 	xor %ecx,%ecx
@@ -90,6 +93,7 @@ SYM_FUNC_START(__put_user_8)
 	cmp %_ASM_BX,%_ASM_CX
 	jae .Lbad_put_user
 SYM_INNER_LABEL(__put_user_nocheck_8, SYM_L_GLOBAL)
+	ENDBR
 	ASM_STAC
 4:	mov %_ASM_AX,(%_ASM_CX)
 #ifdef CONFIG_X86_32