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>

3 files changed, 119 insertions, 0 deletions

diff --git a/arch/xtensa/boot/lib/.gitignore b/arch/xtensa/boot/lib/.gitignore
new file mode 100644
index 000000000..805a82492
--- /dev/null
+++ b/arch/xtensa/boot/lib/.gitignore
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
+inffast.c
+inflate.c
+inftrees.c
diff --git a/arch/xtensa/boot/lib/Makefile b/arch/xtensa/boot/lib/Makefile
new file mode 100644
index 000000000..0378a22a0
--- /dev/null
+++ b/arch/xtensa/boot/lib/Makefile
@@ -0,0 +1,34 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for some libs needed by zImage.
+#
+
+zlib	:= inffast.c inflate.c inftrees.c
+
+lib-y	+= $(zlib:.c=.o) zmem.o
+
+ccflags-y	:= -I $(srctree)/lib/zlib_inflate
+ifdef CONFIG_FUNCTION_TRACER
+CFLAGS_REMOVE_inflate.o = -pg
+CFLAGS_REMOVE_zmem.o = -pg
+CFLAGS_REMOVE_inftrees.o = -pg
+CFLAGS_REMOVE_inffast.o = -pg
+endif
+
+KASAN_SANITIZE := n
+KCSAN_SANITIZE := n
+KCOV_INSTRUMENT := n
+GCOV_PROFILE := n
+
+CFLAGS_REMOVE_inflate.o += -fstack-protector -fstack-protector-strong
+CFLAGS_REMOVE_zmem.o += -fstack-protector -fstack-protector-strong
+CFLAGS_REMOVE_inftrees.o += -fstack-protector -fstack-protector-strong
+CFLAGS_REMOVE_inffast.o += -fstack-protector -fstack-protector-strong
+
+quiet_cmd_copy_zlib = COPY    $@
+      cmd_copy_zlib = cat $< > $@
+
+$(addprefix $(obj)/,$(zlib)): $(obj)/%: $(srctree)/lib/zlib_inflate/%
+	$(call cmd,copy_zlib)
+
+clean-files	:= $(zlib)
diff --git a/arch/xtensa/boot/lib/zmem.c b/arch/xtensa/boot/lib/zmem.c
new file mode 100644
index 000000000..b89189355
--- /dev/null
+++ b/arch/xtensa/boot/lib/zmem.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/zlib.h>
+
+/* bits taken from ppc */
+
+extern void *avail_ram, *end_avail;
+void gunzip(void *dst, int dstlen, unsigned char *src, int *lenp);
+
+static void exit(void)
+{
+  for (;;);
+}
+
+static void *zalloc(unsigned int size)
+{
+        void *p = avail_ram;
+
+        size = (size + 7) & -8;
+        avail_ram += size;
+        if (avail_ram > end_avail) {
+                //puts("oops... out of memory\n");
+                //pause();
+                exit ();
+        }
+        return p;
+}
+
+#define HEAD_CRC        2
+#define EXTRA_FIELD     4
+#define ORIG_NAME       8
+#define COMMENT         0x10
+#define RESERVED        0xe0
+
+#define DEFLATED        8
+
+void gunzip (void *dst, int dstlen, unsigned char *src, int *lenp)
+{
+	z_stream s;
+	int r, i, flags;
+
+        /* skip header */
+        i = 10;
+        flags = src[3];
+        if (src[2] != DEFLATED || (flags & RESERVED) != 0) {
+                //puts("bad gzipped data\n");
+                exit();
+        }
+        if ((flags & EXTRA_FIELD) != 0)
+                i = 12 + src[10] + (src[11] << 8);
+        if ((flags & ORIG_NAME) != 0)
+                while (src[i++] != 0)
+                        ;
+        if ((flags & COMMENT) != 0)
+                while (src[i++] != 0)
+                        ;
+        if ((flags & HEAD_CRC) != 0)
+                i += 2;
+        if (i >= *lenp) {
+                //puts("gunzip: ran out of data in header\n");
+                exit();
+        }
+
+	s.workspace = zalloc(zlib_inflate_workspacesize());
+        r = zlib_inflateInit2(&s, -MAX_WBITS);
+        if (r != Z_OK) {
+                //puts("inflateInit2 returned "); puthex(r); puts("\n");
+                exit();
+        }
+        s.next_in = src + i;
+        s.avail_in = *lenp - i;
+        s.next_out = dst;
+        s.avail_out = dstlen;
+        r = zlib_inflate(&s, Z_FINISH);
+        if (r != Z_OK && r != Z_STREAM_END) {
+                //puts("inflate returned "); puthex(r); puts("\n");
+                exit();
+        }
+        *lenp = s.next_out - (unsigned char *) dst;
+        zlib_inflateEnd(&s);
+}
+