linux-kernel - [PATCH 2/2] kprobes: Use struct_size() in __get_insn

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Message-Id: <20241030-kprobes-fix-counted-by-annotation-v1-2-8f266001fad0@kernel.org>
Date: Wed, 30 Oct 2024 09:14:49 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Masami Hiramatsu <mhiramat@...nel.org>, 
 Naveen N Rao <naveen@...nel.org>, 
 Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>, 
 "David S. Miller" <davem@...emloft.net>
Cc: Kees Cook <kees@...nel.org>, 
 "Gustavo A. R. Silva" <gustavoars@...nel.org>, 
 Jinjie Ruan <ruanjinjie@...wei.com>, linux-kernel@...r.kernel.org, 
 linux-trace-kernel@...r.kernel.org, linux-hardening@...r.kernel.org, 
 patches@...ts.linux.dev, Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH 2/2] kprobes: Use struct_size() in __get_insn_slot()

__get_insn_slot() allocates 'struct kprobe_insn_page' using a custom
structure size calculation macro, KPROBE_INSN_PAGE_SIZE. Replace
KPROBE_INSN_PAGE_SIZE with the struct_size() macro, which is the
preferred way to calculate the size of flexible structures in the kernel
because it handles overflow and makes it easier to change and audit how
flexible structures are allocated across the entire tree.

Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
 kernel/kprobes.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 2cf4628bc97ce2ae18547b513cd75b6350e9cc9c..d452e784b31fa69042229ce0f5ffff9d8b671e92 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -95,10 +95,6 @@ struct kprobe_insn_page {
 	char slot_used[] __counted_by(nused);
 };

-#define KPROBE_INSN_PAGE_SIZE(slots)			\
-	(offsetof(struct kprobe_insn_page, slot_used) +	\
-	 (sizeof(char) * (slots)))
-
 static int slots_per_page(struct kprobe_insn_cache *c)
 {
 	return PAGE_SIZE/(c->insn_size * sizeof(kprobe_opcode_t));
@@ -177,7 +173,7 @@ kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c)
 		goto retry;

 	/* All out of space.  Need to allocate a new page. */
-	kip = kmalloc(KPROBE_INSN_PAGE_SIZE(num_slots), GFP_KERNEL);
+	kip = kmalloc(struct_size(kip, slot_used, num_slots), GFP_KERNEL);
 	if (!kip)
 		goto out;

-- 
2.47.0