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, 121 insertions, 0 deletions

diff --git a/arch/m68k/lib/memmove.c b/arch/m68k/lib/memmove.c
new file mode 100644
index 000000000..e33f00b02
--- /dev/null
+++ b/arch/m68k/lib/memmove.c
@@ -0,0 +1,121 @@
+/*
+ * 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/string.h>
+
+void *memmove(void *dest, const void *src, size_t n)
+{
+	void *xdest = dest;
+	size_t temp;
+
+	if (!n)
+		return xdest;
+
+	if (dest < src) {
+		if ((long)dest & 1) {
+			char *cdest = dest;
+			const char *csrc = src;
+			*cdest++ = *csrc++;
+			dest = cdest;
+			src = csrc;
+			n--;
+		}
+#if defined(CONFIG_M68000)
+		if ((long)src & 1) {
+			char *cdest = dest;
+			const char *csrc = src;
+			for (; n; n--)
+				*cdest++ = *csrc++;
+			return xdest;
+		}
+#endif
+		if (n > 2 && (long)dest & 2) {
+			short *sdest = dest;
+			const short *ssrc = src;
+			*sdest++ = *ssrc++;
+			dest = sdest;
+			src = ssrc;
+			n -= 2;
+		}
+		temp = n >> 2;
+		if (temp) {
+			long *ldest = dest;
+			const long *lsrc = src;
+			temp--;
+			do
+				*ldest++ = *lsrc++;
+			while (temp--);
+			dest = ldest;
+			src = lsrc;
+		}
+		if (n & 2) {
+			short *sdest = dest;
+			const short *ssrc = src;
+			*sdest++ = *ssrc++;
+			dest = sdest;
+			src = ssrc;
+		}
+		if (n & 1) {
+			char *cdest = dest;
+			const char *csrc = src;
+			*cdest = *csrc;
+		}
+	} else {
+		dest = (char *)dest + n;
+		src = (const char *)src + n;
+		if ((long)dest & 1) {
+			char *cdest = dest;
+			const char *csrc = src;
+			*--cdest = *--csrc;
+			dest = cdest;
+			src = csrc;
+			n--;
+		}
+#if defined(CONFIG_M68000)
+		if ((long)src & 1) {
+			char *cdest = dest;
+			const char *csrc = src;
+			for (; n; n--)
+				*--cdest = *--csrc;
+			return xdest;
+		}
+#endif
+		if (n > 2 && (long)dest & 2) {
+			short *sdest = dest;
+			const short *ssrc = src;
+			*--sdest = *--ssrc;
+			dest = sdest;
+			src = ssrc;
+			n -= 2;
+		}
+		temp = n >> 2;
+		if (temp) {
+			long *ldest = dest;
+			const long *lsrc = src;
+			temp--;
+			do
+				*--ldest = *--lsrc;
+			while (temp--);
+			dest = ldest;
+			src = lsrc;
+		}
+		if (n & 2) {
+			short *sdest = dest;
+			const short *ssrc = src;
+			*--sdest = *--ssrc;
+			dest = sdest;
+			src = ssrc;
+		}
+		if (n & 1) {
+			char *cdest = dest;
+			const char *csrc = src;
+			*--cdest = *--csrc;
+		}
+	}
+	return xdest;
+}
+EXPORT_SYMBOL(memmove);