x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 204 insertions, 0 deletions

diff --git a/drivers/ssb/sprom.c b/drivers/ssb/sprom.c
new file mode 100644
index 000000000..7cd553127
--- /dev/null
+++ b/drivers/ssb/sprom.c
@@ -0,0 +1,204 @@
+/*
+ * Sonics Silicon Backplane
+ * Common SPROM support routines
+ *
+ * Copyright (C) 2005-2008 Michael Buesch <m@bues.ch>
+ * Copyright (C) 2005 Martin Langer <martin-langer@gmx.de>
+ * Copyright (C) 2005 Stefano Brivio <st3@riseup.net>
+ * Copyright (C) 2005 Danny van Dyk <kugelfang@gentoo.org>
+ * Copyright (C) 2005 Andreas Jaggi <andreas.jaggi@waterwave.ch>
+ *
+ * Licensed under the GNU/GPL. See COPYING for details.
+ */
+
+#include "ssb_private.h"
+
+#include <linux/ctype.h>
+#include <linux/slab.h>
+
+
+static int(*get_fallback_sprom)(struct ssb_bus *dev, struct ssb_sprom *out);
+
+
+static int sprom2hex(const u16 *sprom, char *buf, size_t buf_len,
+		     size_t sprom_size_words)
+{
+	int i, pos = 0;
+
+	for (i = 0; i < sprom_size_words; i++)
+		pos += scnprintf(buf + pos, buf_len - pos - 1,
+				"%04X", swab16(sprom[i]) & 0xFFFF);
+	pos += scnprintf(buf + pos, buf_len - pos - 1, "\n");
+
+	return pos + 1;
+}
+
+static int hex2sprom(u16 *sprom, const char *dump, size_t len,
+		     size_t sprom_size_words)
+{
+	char c, tmp[5] = { 0 };
+	int err, cnt = 0;
+	unsigned long parsed;
+
+	/* Strip whitespace at the end. */
+	while (len) {
+		c = dump[len - 1];
+		if (!isspace(c) && c != '\0')
+			break;
+		len--;
+	}
+	/* Length must match exactly. */
+	if (len != sprom_size_words * 4)
+		return -EINVAL;
+
+	while (cnt < sprom_size_words) {
+		memcpy(tmp, dump, 4);
+		dump += 4;
+		err = kstrtoul(tmp, 16, &parsed);
+		if (err)
+			return err;
+		sprom[cnt++] = swab16((u16)parsed);
+	}
+
+	return 0;
+}
+
+/* Common sprom device-attribute show-handler */
+ssize_t ssb_attr_sprom_show(struct ssb_bus *bus, char *buf,
+			    int (*sprom_read)(struct ssb_bus *bus, u16 *sprom))
+{
+	u16 *sprom;
+	int err = -ENOMEM;
+	ssize_t count = 0;
+	size_t sprom_size_words = bus->sprom_size;
+
+	sprom = kcalloc(sprom_size_words, sizeof(u16), GFP_KERNEL);
+	if (!sprom)
+		goto out;
+
+	/* Use interruptible locking, as the SPROM write might
+	 * be holding the lock for several seconds. So allow userspace
+	 * to cancel operation.
+	 */
+	err = -ERESTARTSYS;
+	if (mutex_lock_interruptible(&bus->sprom_mutex))
+		goto out_kfree;
+	err = sprom_read(bus, sprom);
+	mutex_unlock(&bus->sprom_mutex);
+
+	if (!err)
+		count = sprom2hex(sprom, buf, PAGE_SIZE, sprom_size_words);
+
+out_kfree:
+	kfree(sprom);
+out:
+	return err ? err : count;
+}
+
+/* Common sprom device-attribute store-handler */
+ssize_t ssb_attr_sprom_store(struct ssb_bus *bus,
+			     const char *buf, size_t count,
+			     int (*sprom_check_crc)(const u16 *sprom, size_t size),
+			     int (*sprom_write)(struct ssb_bus *bus, const u16 *sprom))
+{
+	u16 *sprom;
+	int res = 0, err = -ENOMEM;
+	size_t sprom_size_words = bus->sprom_size;
+	struct ssb_freeze_context freeze;
+
+	sprom = kcalloc(bus->sprom_size, sizeof(u16), GFP_KERNEL);
+	if (!sprom)
+		goto out;
+	err = hex2sprom(sprom, buf, count, sprom_size_words);
+	if (err) {
+		err = -EINVAL;
+		goto out_kfree;
+	}
+	err = sprom_check_crc(sprom, sprom_size_words);
+	if (err) {
+		err = -EINVAL;
+		goto out_kfree;
+	}
+
+	/* Use interruptible locking, as the SPROM write might
+	 * be holding the lock for several seconds. So allow userspace
+	 * to cancel operation.
+	 */
+	err = -ERESTARTSYS;
+	if (mutex_lock_interruptible(&bus->sprom_mutex))
+		goto out_kfree;
+	err = ssb_devices_freeze(bus, &freeze);
+	if (err) {
+		pr_err("SPROM write: Could not freeze all devices\n");
+		goto out_unlock;
+	}
+	res = sprom_write(bus, sprom);
+	err = ssb_devices_thaw(&freeze);
+	if (err)
+		pr_err("SPROM write: Could not thaw all devices\n");
+out_unlock:
+	mutex_unlock(&bus->sprom_mutex);
+out_kfree:
+	kfree(sprom);
+out:
+	if (res)
+		return res;
+	return err ? err : count;
+}
+
+/**
+ * ssb_arch_register_fallback_sprom - Registers a method providing a
+ * fallback SPROM if no SPROM is found.
+ *
+ * @sprom_callback: The callback function.
+ *
+ * With this function the architecture implementation may register a
+ * callback handler which fills the SPROM data structure. The fallback is
+ * only used for PCI based SSB devices, where no valid SPROM can be found
+ * in the shadow registers.
+ *
+ * This function is useful for weird architectures that have a half-assed
+ * SSB device hardwired to their PCI bus.
+ *
+ * Note that it does only work with PCI attached SSB devices. PCMCIA
+ * devices currently don't use this fallback.
+ * Architectures must provide the SPROM for native SSB devices anyway, so
+ * the fallback also isn't used for native devices.
+ *
+ * This function is available for architecture code, only. So it is not
+ * exported.
+ */
+int ssb_arch_register_fallback_sprom(int (*sprom_callback)(struct ssb_bus *bus,
+				     struct ssb_sprom *out))
+{
+	if (get_fallback_sprom)
+		return -EEXIST;
+	get_fallback_sprom = sprom_callback;
+
+	return 0;
+}
+
+int ssb_fill_sprom_with_fallback(struct ssb_bus *bus, struct ssb_sprom *out)
+{
+	if (!get_fallback_sprom)
+		return -ENOENT;
+
+	return get_fallback_sprom(bus, out);
+}
+
+/* https://bcm-v4.sipsolutions.net/802.11/IsSpromAvailable */
+bool ssb_is_sprom_available(struct ssb_bus *bus)
+{
+	/* status register only exists on chipcomon rev >= 11 and we need check
+	 * for >= 31 only
+	 */
+	/* this routine differs from specs as we do not access SPROM directly
+	 * on PCMCIA
+	 */
+	if (bus->bustype == SSB_BUSTYPE_PCI &&
+	    bus->chipco.dev &&	/* can be unavailable! */
+	    bus->chipco.dev->id.revision >= 31)
+		return bus->chipco.capabilities & SSB_CHIPCO_CAP_SPROM;
+
+	return true;
+}