linux-kernel - [PATCH v6.6] riscv: uprobes: Add missing fence.i after building the XOL buffer

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Message-Id: <20260114011830.2045424-1-black.hawk@163.com>
Date: Wed, 14 Jan 2026 09:18:30 +0800
From: Rahul Sharma <black.hawk@....com>
To: gregkh@...uxfoundation.org,
	stable@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	Björn Töpel <bjorn@...osinc.com>,
	Guo Ren <guoren@...nel.org>,
	Palmer Dabbelt <palmer@...osinc.com>,
	Rahul Sharma <black.hawk@....com>
Subject: [PATCH v6.6] riscv: uprobes: Add missing fence.i after building the XOL buffer

From: Björn Töpel <bjorn@...osinc.com>

[ Upstream commit 7d1d19a11cfbfd8bae1d89cc010b2cc397cd0c48 ]

The XOL (execute out-of-line) buffer is used to single-step the
replaced instruction(s) for uprobes. The RISC-V port was missing a
proper fence.i (i$ flushing) after constructing the XOL buffer, which
can result in incorrect execution of stale/broken instructions.

This was found running the BPF selftests "test_progs:
uprobe_autoattach, attach_probe" on the Spacemit K1/X60, where the
uprobes tests randomly blew up.

Reviewed-by: Guo Ren <guoren@...nel.org>
Fixes: 74784081aac8 ("riscv: Add uprobes supported")
Signed-off-by: Björn Töpel <bjorn@...osinc.com>
Link: https://lore.kernel.org/r/20250419111402.1660267-2-bjorn@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@...osinc.com>
Signed-off-by: Rahul Sharma <black.hawk@....com>
---
 arch/riscv/kernel/probes/uprobes.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/arch/riscv/kernel/probes/uprobes.c b/arch/riscv/kernel/probes/uprobes.c
index 4b3dc8beaf77..cc15f7ca6cc1 100644
--- a/arch/riscv/kernel/probes/uprobes.c
+++ b/arch/riscv/kernel/probes/uprobes.c
@@ -167,6 +167,7 @@ void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
 	/* Initialize the slot */
 	void *kaddr = kmap_atomic(page);
 	void *dst = kaddr + (vaddr & ~PAGE_MASK);
+	unsigned long start = (unsigned long)dst;
 
 	memcpy(dst, src, len);
 
@@ -176,13 +177,6 @@ void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
 		*(uprobe_opcode_t *)dst = __BUG_INSN_32;
 	}
 
+	flush_icache_range(start, start + len);
 	kunmap_atomic(kaddr);
-
-	/*
-	 * We probably need flush_icache_user_page() but it needs vma.
-	 * This should work on most of architectures by default. If
-	 * architecture needs to do something different it can define
-	 * its own version of the function.
-	 */
-	flush_dcache_page(page);
 }
-- 
2.34.1