linux-kernel - [PATCH] crash_core: optimize crash_exclude_mem

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Date: Wed, 20 Dec 2023 00:34:18 +0800
From: Yuntao Wang <ytcoode@...il.com>
To: akpm@...ux-foundation.org
Cc: bhe@...hat.com,
	bp@...en8.de,
	dave.hansen@...ux.intel.com,
	dyoung@...hat.com,
	hbathini@...ux.ibm.com,
	hpa@...or.com,
	kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	mingo@...hat.com,
	seanjc@...gle.com,
	tglx@...utronix.de,
	tiwai@...e.de,
	vgoyal@...hat.com,
	x86@...nel.org,
	ytcoode@...il.com
Subject: [PATCH] crash_core: optimize crash_exclude_mem_range()

Because memory ranges in mem->ranges are stored in ascending order, when we
detect `p_end < start`, we can break the for loop early, as the subsequent
memory ranges must also be outside the range we are looking for.

Signed-off-by: Yuntao Wang <ytcoode@...il.com>
---
Hi Andrew,

Patch "[PATCH 2/2] crash_core: fix out-of-bounds access check in
crash_exclude_mem_range()" can be ignored, use this patch instead.

 kernel/crash_core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 9a219a918638..d425c4a106cd 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -575,9 +575,12 @@ int crash_exclude_mem_range(struct crash_mem *mem,
 		p_start = mstart;
 		p_end = mend;
 
-		if (p_start > end || p_end < start)
+		if (p_start > end)
 			continue;
 
+		if (p_end < start)
+			break;
+
 		/* Truncate any area outside of range */
 		if (p_start < start)
 			p_start = start;
-- 
2.43.0