selftests/bpf: Test packet range of pointers sharing an idgrafted

Add tests where two packet pointers share an id and tightening one
pointer's umax from its var_off would put it less than their constant
distance from the other's umax: with an index & 0x38 capped at 50, the
base pointer keeps umax 50, so the pointer 8 bytes further on must keep
umax 58, even though its known bits allow at most 56.

These refused a valid program or accepted an out-of-bounds access before
the fix:

- check the advanced copy, load through the base: valid, was refused;
- check the base, load the byte at base + 1 through a copy advanced by
  8: was accepted;
- check base + 4, load 4 bytes at base + 2 through base + 8: reads two
  bytes past the checked range, was accepted;
- the same as the second with data_meta pointers checked against data:
  was accepted.

These pass with and without the fix and cover nearby paths:

- subtract an unknown scalar from a checked pointer and load below it
  (the range is kept across a new id);
- reach a load through two paths whose checks cover 8 and 7 bytes after
  the loaded pointer; the second path must not be pruned by the first;
- spill a copy of a pointer, check the pointer, fill the copy and load
  one byte past the checked range: the load is refused, and the copy
  has the range of the check.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20261001145255.855630-2-alexei.starovoitov@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

1 files changed, 80 insertions, 0 deletions

diff --git a/drivers/s390/char/ctrlchar.c b/drivers/s390/char/ctrlchar.c
new file mode 100644
index 000000000..6f2b64040
--- /dev/null
+++ b/drivers/s390/char/ctrlchar.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Unified handling of special chars.
+ *
+ *    Copyright IBM Corp. 2001
+ *    Author(s): Fritz Elfert <felfert@millenux.com> <elfert@de.ibm.com>
+ *
+ */
+
+#include <linux/stddef.h>
+#include <asm/errno.h>
+#include <linux/sysrq.h>
+#include <linux/ctype.h>
+
+#include "ctrlchar.h"
+
+#ifdef CONFIG_MAGIC_SYSRQ
+static struct sysrq_work ctrlchar_sysrq;
+
+static void
+ctrlchar_handle_sysrq(struct work_struct *work)
+{
+	struct sysrq_work *sysrq = container_of(work, struct sysrq_work, work);
+
+	handle_sysrq(sysrq->key);
+}
+
+void schedule_sysrq_work(struct sysrq_work *sw)
+{
+	INIT_WORK(&sw->work, ctrlchar_handle_sysrq);
+	schedule_work(&sw->work);
+}
+#endif
+
+
+/**
+ * ctrlchar_handle - check for special chars at start of input
+ *
+ * @buf: console input buffer
+ * @len: length of valid data in buffer
+ * @tty: the tty struct for this console
+ *
+ * Return: CTRLCHAR_NONE, if nothing matched,
+ *         CTRLCHAR_SYSRQ, if sysrq was encountered
+ *         otherwise char to be inserted logically or'ed
+ *         with CTRLCHAR_CTRL
+ */
+unsigned int
+ctrlchar_handle(const unsigned char *buf, int len, struct tty_struct *tty)
+{
+	if ((len < 2) || (len > 3))
+		return CTRLCHAR_NONE;
+
+	/* hat is 0xb1 in codepage 037 (US etc.) and thus */
+	/* converted to 0x5e in ascii ('^') */
+	if ((buf[0] != '^') && (buf[0] != '\252'))
+		return CTRLCHAR_NONE;
+
+#ifdef CONFIG_MAGIC_SYSRQ
+	/* racy */
+	if (len == 3 && buf[1] == '-') {
+		ctrlchar_sysrq.key = buf[2];
+		schedule_sysrq_work(&ctrlchar_sysrq);
+		return CTRLCHAR_SYSRQ;
+	}
+#endif
+
+	if (len != 2)
+		return CTRLCHAR_NONE;
+
+	switch (tolower(buf[1])) {
+	case 'c':
+		return INTR_CHAR(tty) | CTRLCHAR_CTRL;
+	case 'd':
+		return EOF_CHAR(tty)  | CTRLCHAR_CTRL;
+	case 'z':
+		return SUSP_CHAR(tty) | CTRLCHAR_CTRL;
+	}
+	return CTRLCHAR_NONE;
+}