linux-kernel - [PATCH stable v6.6] riscv: kprobes: Fix wrong lengths passed to patch_text

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Message-Id: <20250429161418.838564-1-namcao@linutronix.de>
Date: Tue, 29 Apr 2025 18:14:18 +0200
From: Nam Cao <namcao@...utronix.de>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org
Cc: Kai Zhang <zhangkai@...as.ac.cn>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Alexandre Ghiti <alex@...ti.fr>,
	Samuel Holland <samuel.holland@...ive.com>,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Nam Cao <namcao@...utronix.de>
Subject: [PATCH stable v6.6] riscv: kprobes: Fix wrong lengths passed to patch_text_nosync()

Unlike patch_text(), patch_text_nosync() takes the length in bytes, not
number of instructions. It is therefore wrong for arch_prepare_ss_slot() to
pass length=1 while patching one instruction.

This bug was introduced by commit b1756750a397 ("riscv: kprobes: Use
patch_text_nosync() for insn slots"). It has been fixed upstream by commit
51781ce8f448 ("riscv: Pass patch_text() the length in bytes"). However,
beside fixing this bug, this commit does many other things, making it
unsuitable for backporting.

Fix it by properly passing the lengths in bytes.

Fixes: b1756750a397 ("riscv: kprobes: Use patch_text_nosync() for insn slots")
Signed-off-by: Nam Cao <namcao@...utronix.de>
---
 arch/riscv/kernel/probes/kprobes.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c
index 4fbc70e823f0..dc431b965bc3 100644
--- a/arch/riscv/kernel/probes/kprobes.c
+++ b/arch/riscv/kernel/probes/kprobes.c
@@ -28,8 +28,8 @@ static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
 
 	p->ainsn.api.restore = (unsigned long)p->addr + offset;
 
-	patch_text_nosync(p->ainsn.api.insn, &p->opcode, 1);
-	patch_text_nosync((void *)p->ainsn.api.insn + offset, &insn, 1);
+	patch_text_nosync(p->ainsn.api.insn, &p->opcode, offset);
+	patch_text_nosync((void *)p->ainsn.api.insn + offset, &insn, sizeof(insn));
 }
 
 static void __kprobes arch_prepare_simulate(struct kprobe *p)
-- 
2.39.5