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, 110 insertions, 0 deletions

diff --git a/arch/m68k/atari/atasound.c b/arch/m68k/atari/atasound.c
new file mode 100644
index 000000000..c38ef0e60
--- /dev/null
+++ b/arch/m68k/atari/atasound.c
@@ -0,0 +1,110 @@
+/*
+ * linux/arch/m68k/atari/atasound.c
+ *
+ * ++Geert: Moved almost all stuff to linux/drivers/sound/
+ *
+ * The author of atari_nosound, atari_mksound and atari_microwire_cmd is
+ * unknown. (++roman: That's me... :-)
+ *
+ * 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.
+ *
+ * 1998-05-31 ++andreas: atari_mksound rewritten to always use the envelope,
+ *			 no timer, atari_nosound removed.
+ *
+ */
+
+
+#include <linux/sched.h>
+#include <linux/timer.h>
+#include <linux/major.h>
+#include <linux/fcntl.h>
+#include <linux/errno.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+
+#include <asm/atarihw.h>
+#include <asm/irq.h>
+#include <asm/atariints.h>
+
+#include "atari.h"
+
+/*
+ * stuff from the old atasound.c
+ */
+
+void atari_microwire_cmd (int cmd)
+{
+	tt_microwire.mask = 0x7ff;
+	tt_microwire.data = MW_LM1992_ADDR | cmd;
+
+	/* Busy wait for data being completely sent :-( */
+	while( tt_microwire.mask != 0x7ff)
+		;
+}
+EXPORT_SYMBOL(atari_microwire_cmd);
+
+
+/* PSG base frequency */
+#define	PSG_FREQ	125000
+/* PSG envelope base frequency times 10 */
+#define PSG_ENV_FREQ_10	78125
+
+void atari_mksound (unsigned int hz, unsigned int ticks)
+{
+	/* Generates sound of some frequency for some number of clock
+	   ticks.  */
+	unsigned long flags;
+	unsigned char tmp;
+	int period;
+
+	local_irq_save(flags);
+
+
+	/* Disable generator A in mixer control.  */
+	sound_ym.rd_data_reg_sel = 7;
+	tmp = sound_ym.rd_data_reg_sel;
+	tmp |= 011;
+	sound_ym.wd_data = tmp;
+
+	if (hz) {
+	    /* Convert from frequency value to PSG period value (base
+	       frequency 125 kHz).  */
+
+	    period = PSG_FREQ / hz;
+
+	    if (period > 0xfff) period = 0xfff;
+
+	/* Set generator A frequency to hz.  */
+	sound_ym.rd_data_reg_sel = 0;
+	sound_ym.wd_data = period & 0xff;
+	sound_ym.rd_data_reg_sel = 1;
+	sound_ym.wd_data = (period >> 8) & 0xf;
+	if (ticks) {
+		/* Set length of envelope (max 8 sec).  */
+		int length = (ticks * PSG_ENV_FREQ_10) / HZ / 10;
+
+		if (length > 0xffff) length = 0xffff;
+		sound_ym.rd_data_reg_sel = 11;
+		sound_ym.wd_data = length & 0xff;
+		sound_ym.rd_data_reg_sel = 12;
+		sound_ym.wd_data = length >> 8;
+		/* Envelope form: max -> min single.  */
+		sound_ym.rd_data_reg_sel = 13;
+		sound_ym.wd_data = 0;
+		/* Use envelope for generator A.  */
+		sound_ym.rd_data_reg_sel = 8;
+		sound_ym.wd_data = 0x10;
+	} else {
+		/* Set generator A level to maximum, no envelope.  */
+		sound_ym.rd_data_reg_sel = 8;
+		sound_ym.wd_data = 15;
+	}
+	/* Turn on generator A in mixer control.  */
+	sound_ym.rd_data_reg_sel = 7;
+	tmp &= ~1;
+	sound_ym.wd_data = tmp;
+	}
+	local_irq_restore(flags);
+}