From: Kees Cook <keescook@chromium.org>
To: Andrew Jeffery <andrew@aj.id.au>
Cc: linux-kernel@vger.kernel.org, linux@armlinux.org.uk,
mathieu.desnoyers@efficios.com, mhiramat@kernel.org,
labbott@redhat.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] ARM: kprobes: Avoid fortify_panic() when copying optprobe template
Date: Sun, 17 May 2020 14:48:52 -0700 [thread overview]
Message-ID: <202005171447.00CFE0C@keescook> (raw)
In-Reply-To: <20200517153959.293224-1-andrew@aj.id.au>
On Mon, May 18, 2020 at 01:09:59AM +0930, Andrew Jeffery wrote:
> As mentioned, a couple of attempts have been made to address the issue
> by casting a pointer to optprobe_template_entry before providing it to
> memcpy(), however gccs such as Ubuntu 20.04's arm-linux-gnueabi-gcc
> 9.3.0 (Ubuntu 9.3.0-10ubuntu1) see through these efforts.
Ah, dang. :P
How about converting them all to unsized arrays, which would also allow
the code to drop the "&" everywhere, I think. This is untested:
diff --git a/arch/arm/include/asm/kprobes.h b/arch/arm/include/asm/kprobes.h
index 213607a1f45c..e26a278d301a 100644
--- a/arch/arm/include/asm/kprobes.h
+++ b/arch/arm/include/asm/kprobes.h
@@ -44,20 +44,20 @@ int kprobe_exceptions_notify(struct notifier_block *self,
unsigned long val, void *data);
/* optinsn template addresses */
-extern __visible kprobe_opcode_t optprobe_template_entry;
-extern __visible kprobe_opcode_t optprobe_template_val;
-extern __visible kprobe_opcode_t optprobe_template_call;
-extern __visible kprobe_opcode_t optprobe_template_end;
-extern __visible kprobe_opcode_t optprobe_template_sub_sp;
-extern __visible kprobe_opcode_t optprobe_template_add_sp;
-extern __visible kprobe_opcode_t optprobe_template_restore_begin;
-extern __visible kprobe_opcode_t optprobe_template_restore_orig_insn;
-extern __visible kprobe_opcode_t optprobe_template_restore_end;
+extern __visible kprobe_opcode_t optprobe_template_entry[];
+extern __visible kprobe_opcode_t optprobe_template_val[];
+extern __visible kprobe_opcode_t optprobe_template_call[];
+extern __visible kprobe_opcode_t optprobe_template_end[];
+extern __visible kprobe_opcode_t optprobe_template_sub_sp[];
+extern __visible kprobe_opcode_t optprobe_template_add_sp[];
+extern __visible kprobe_opcode_t optprobe_template_restore_begin[];
+extern __visible kprobe_opcode_t optprobe_template_restore_orig_insn[];
+extern __visible kprobe_opcode_t optprobe_template_restore_end[];
#define MAX_OPTIMIZED_LENGTH 4
#define MAX_OPTINSN_SIZE \
- ((unsigned long)&optprobe_template_end - \
- (unsigned long)&optprobe_template_entry)
+ ((unsigned long)optprobe_template_end - \
+ (unsigned long)optprobe_template_entry)
#define RELATIVEJUMP_SIZE 4
struct arch_optimized_insn {
diff --git a/arch/arm/probes/kprobes/opt-arm.c b/arch/arm/probes/kprobes/opt-arm.c
index 7a449df0b359..c78180172120 100644
--- a/arch/arm/probes/kprobes/opt-arm.c
+++ b/arch/arm/probes/kprobes/opt-arm.c
@@ -85,21 +85,21 @@ asm (
"optprobe_template_end:\n");
#define TMPL_VAL_IDX \
- ((unsigned long *)&optprobe_template_val - (unsigned long *)&optprobe_template_entry)
+ ((unsigned long *)optprobe_template_val - (unsigned long *)optprobe_template_entry)
#define TMPL_CALL_IDX \
- ((unsigned long *)&optprobe_template_call - (unsigned long *)&optprobe_template_entry)
+ ((unsigned long *)optprobe_template_call - (unsigned long *)optprobe_template_entry)
#define TMPL_END_IDX \
- ((unsigned long *)&optprobe_template_end - (unsigned long *)&optprobe_template_entry)
+ ((unsigned long *)optprobe_template_end - (unsigned long *)optprobe_template_entry)
#define TMPL_ADD_SP \
- ((unsigned long *)&optprobe_template_add_sp - (unsigned long *)&optprobe_template_entry)
+ ((unsigned long *)optprobe_template_add_sp - (unsigned long *)optprobe_template_entry)
#define TMPL_SUB_SP \
- ((unsigned long *)&optprobe_template_sub_sp - (unsigned long *)&optprobe_template_entry)
+ ((unsigned long *)optprobe_template_sub_sp - (unsigned long *)optprobe_template_entry)
#define TMPL_RESTORE_BEGIN \
- ((unsigned long *)&optprobe_template_restore_begin - (unsigned long *)&optprobe_template_entry)
+ ((unsigned long *)optprobe_template_restore_begin - (unsigned long *)optprobe_template_entry)
#define TMPL_RESTORE_ORIGN_INSN \
- ((unsigned long *)&optprobe_template_restore_orig_insn - (unsigned long *)&optprobe_template_entry)
+ ((unsigned long *)optprobe_template_restore_orig_insn - (unsigned long *)optprobe_template_entry)
#define TMPL_RESTORE_END \
- ((unsigned long *)&optprobe_template_restore_end - (unsigned long *)&optprobe_template_entry)
+ ((unsigned long *)optprobe_template_restore_end - (unsigned long *)optprobe_template_entry)
/*
* ARM can always optimize an instruction when using ARM ISA, except
@@ -234,7 +234,7 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *or
}
/* Copy arch-dep-instance from template. */
- memcpy(code, (unsigned long *)&optprobe_template_entry,
+ memcpy(code, (unsigned long *)optprobe_template_entry,
TMPL_END_IDX * sizeof(kprobe_opcode_t));
/* Adjust buffer according to instruction. */
--
Kees Cook
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-05-17 21:48 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-17 15:39 [PATCH] ARM: kprobes: Avoid fortify_panic() when copying optprobe template Andrew Jeffery
2020-05-17 16:02 ` Russell King - ARM Linux admin
2020-05-18 8:10 ` Andrew Jeffery
2020-05-17 21:48 ` Kees Cook [this message]
2020-05-18 0:49 ` Andrew Jeffery
2020-05-18 2:20 ` Masami Hiramatsu
2020-05-19 0:22 ` Andrew Jeffery
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