bpf: mark a NULL kfunc argument precisegrafted

check_kfunc_arg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.

Fixes: 3bda08b63670 ("bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-5-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 142 insertions, 0 deletions

diff --git a/arch/m68k/lib/uaccess.c b/arch/m68k/lib/uaccess.c
new file mode 100644
index 000000000..7646e461a
--- /dev/null
+++ b/arch/m68k/lib/uaccess.c
@@ -0,0 +1,142 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/uaccess.h>
+
+unsigned long __generic_copy_from_user(void *to, const void __user *from,
+				       unsigned long n)
+{
+	unsigned long tmp, res;
+
+	asm volatile ("\n"
+		"	tst.l	%0\n"
+		"	jeq	2f\n"
+		"1:	"MOVES".l	(%1)+,%3\n"
+		"	move.l	%3,(%2)+\n"
+		"	subq.l	#1,%0\n"
+		"	jne	1b\n"
+		"2:	btst	#1,%5\n"
+		"	jeq	4f\n"
+		"3:	"MOVES".w	(%1)+,%3\n"
+		"	move.w	%3,(%2)+\n"
+		"4:	btst	#0,%5\n"
+		"	jeq	6f\n"
+		"5:	"MOVES".b	(%1)+,%3\n"
+		"	move.b  %3,(%2)+\n"
+		"6:\n"
+		"	.section .fixup,\"ax\"\n"
+		"	.even\n"
+		"10:	lsl.l	#2,%0\n"
+		"	btst	#1,%5\n"
+		"	jeq	8f\n"
+		"30:	addq.l	#2,%0\n"
+		"8:	btst	#0,%5\n"
+		"	jeq	6b\n"
+		"50:	addq.l	#1,%0\n"
+		"	jra	6b\n"
+		"	.previous\n"
+		"\n"
+		"	.section __ex_table,\"a\"\n"
+		"	.align	4\n"
+		"	.long	1b,10b\n"
+		"	.long	3b,30b\n"
+		"	.long	5b,50b\n"
+		"	.previous"
+		: "=d" (res), "+a" (from), "+a" (to), "=&d" (tmp)
+		: "0" (n / 4), "d" (n & 3));
+
+	return res;
+}
+EXPORT_SYMBOL(__generic_copy_from_user);
+
+unsigned long __generic_copy_to_user(void __user *to, const void *from,
+				     unsigned long n)
+{
+	unsigned long tmp, res;
+
+	asm volatile ("\n"
+		"	tst.l	%0\n"
+		"	jeq	4f\n"
+		"1:	move.l	(%1)+,%3\n"
+		"2:	"MOVES".l	%3,(%2)+\n"
+		"3:	subq.l	#1,%0\n"
+		"	jne	1b\n"
+		"4:	btst	#1,%5\n"
+		"	jeq	6f\n"
+		"	move.w	(%1)+,%3\n"
+		"5:	"MOVES".w	%3,(%2)+\n"
+		"6:	btst	#0,%5\n"
+		"	jeq	8f\n"
+		"	move.b	(%1)+,%3\n"
+		"7:	"MOVES".b  %3,(%2)+\n"
+		"8:\n"
+		"	.section .fixup,\"ax\"\n"
+		"	.even\n"
+		"20:	lsl.l	#2,%0\n"
+		"50:	add.l	%5,%0\n"
+		"	jra	8b\n"
+		"	.previous\n"
+		"\n"
+		"	.section __ex_table,\"a\"\n"
+		"	.align	4\n"
+		"	.long	2b,20b\n"
+		"	.long	3b,20b\n"
+		"	.long	5b,50b\n"
+		"	.long	6b,50b\n"
+		"	.long	7b,50b\n"
+		"	.long	8b,50b\n"
+		"	.previous"
+		: "=d" (res), "+a" (from), "+a" (to), "=&d" (tmp)
+		: "0" (n / 4), "d" (n & 3));
+
+	return res;
+}
+EXPORT_SYMBOL(__generic_copy_to_user);
+
+/*
+ * Zero Userspace
+ */
+
+unsigned long __clear_user(void __user *to, unsigned long n)
+{
+	unsigned long res;
+
+	asm volatile ("\n"
+		"	tst.l	%0\n"
+		"	jeq	3f\n"
+		"1:	"MOVES".l	%2,(%1)+\n"
+		"2:	subq.l	#1,%0\n"
+		"	jne	1b\n"
+		"3:	btst	#1,%4\n"
+		"	jeq	5f\n"
+		"4:	"MOVES".w	%2,(%1)+\n"
+		"5:	btst	#0,%4\n"
+		"	jeq	7f\n"
+		"6:	"MOVES".b	%2,(%1)\n"
+		"7:\n"
+		"	.section .fixup,\"ax\"\n"
+		"	.even\n"
+		"10:	lsl.l	#2,%0\n"
+		"40:	add.l	%4,%0\n"
+		"	jra	7b\n"
+		"	.previous\n"
+		"\n"
+		"	.section __ex_table,\"a\"\n"
+		"	.align	4\n"
+		"	.long	1b,10b\n"
+		"	.long	2b,10b\n"
+		"	.long	4b,40b\n"
+		"	.long	5b,40b\n"
+		"	.long	6b,40b\n"
+		"	.long	7b,40b\n"
+		"	.previous"
+		: "=d" (res), "+a" (to)
+		: "d" (0), "0" (n / 4), "d" (n & 3));
+
+    return res;
+}
+EXPORT_SYMBOL(__clear_user);