[PATCH 6.6 053/105] riscv: kprobes: Fix probe address validation

Greg Kroah-Hartman
2025-10-21T19:57:47Z

From: Fabian Vogt <fvogt@suse.de>

[ Upstream commit 9e68bd803fac49274fde914466fd3b07c4d602c8 ]

When adding a kprobe such as "p:probe/tcp_sendmsg _text+15392192",
arch_check_kprobe would start iterating all instructions starting from
_text until the probed address. Not only is this very inefficient, but
literal values in there (e.g. left by function patching) are
misinterpreted in a way that causes a desync.

Fix this by doing it like x86: start the iteration at the closest
preceding symbol instead of the given starting point.

Fixes: 87f48c7ccc73 ("riscv: kprobe: Fixup kernel panic when probing an illegal position")
Signed-off-by: Fabian Vogt <fvogt@suse.de>
Signed-off-by: Marvin Friedrich <marvin.friedrich@suse.com>
Acked-by: Guo Ren <guoren@kernel.org>
Link: https://lore.kernel.org/r/6191817.lOV4Wx5bFT@fvogt-thinkpad
Signed-off-by: Paul Walmsley <pjw@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/riscv/kernel/probes/kprobes.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c
index 297427ffc4e04..8a6ea7d270188 100644
--- a/arch/riscv/kernel/probes/kprobes.c
+++ b/arch/riscv/kernel/probes/kprobes.c
@@ -48,10 +48,15 @@ static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
post_kprobe_handler(p, kcb, regs);
}

-static bool __kprobes arch_check_kprobe(struct kprobe *p)
+static bool __kprobes arch_check_kprobe(unsigned long addr)
{
- unsigned long tmp = (unsigned long)p->addr - p->offset;
- unsigned long addr = (unsigned long)p->addr;
+ unsigned long tmp, offset;
+
+ /* start iterating at the closest preceding symbol */
+ if (!kallsyms_lookup_size_offset(addr, NULL, &offset))
+ return false;
+
+ tmp = addr - offset;

while (tmp <= addr) {
if (tmp == addr)
@@ -70,7 +75,7 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
if ((unsigned long)insn & 0x1)
return -EILSEQ;

- if (!arch_check_kprobe(p))
+ if (!arch_check_kprobe((unsigned long)p->addr))
return -EILSEQ;

/* copy instruction */
--
2.51.0