[PATCH] Before adding to usablemem_rgns, check if the memory range is already included.

[Chen Haixiang]

When kexec_iomem_for_each_line() reads from /proc/iomem,
concurrent modifications to /proc/iomem may lead to
usablemem_rgns recording duplicate Crash kernel segments.
This can result in the number of retrieved Crash kernel
segments exceeding CRASH_MAX_RESERVED_RANGES, triggering
a realloc of the crash_reserved_mem in usablemem_rgns,
which could crash the process. We should ensure that each
range added to usablemem_rgns is unique to prevent these issues.
---
 kexec/arch/arm64/crashdump-arm64.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/kexec/arch/arm64/crashdump-arm64.c b/kexec/arch/arm64/crashdump-arm64.c
index 3098315..f23b2bf 100644
--- a/kexec/arch/arm64/crashdump-arm64.c
+++ b/kexec/arch/arm64/crashdump-arm64.c
@@ -63,10 +63,22 @@ static int iomem_range_callback(void *UNUSED(data), int UNUSED(nr),
 				char *str, unsigned long long base,
 				unsigned long long length)
 {
-	if (strncmp(str, CRASH_KERNEL, strlen(CRASH_KERNEL)) == 0)
+	int i;
+
+	if (strncmp(str, CRASH_KERNEL, strlen(CRASH_KERNEL)) == 0) {
+		/*
+		 * Checks whether the area exists in crash_reserved_mem.
+		 */
+		for (i = 0; i < usablemem_rgns.max_size; i++) {
+			if (usablemem_rgns.ranges[i].start == base) {
+				fprintf(stderr, "Warning, the range already exists in usablemem_rgns, base=%lx, length=%lx\n",
+						base, length);
+				return 0;
+			}
+		}
 		return mem_regions_alloc_and_add(&usablemem_rgns,
 						base, length, RANGE_RAM);
-	else if (strncmp(str, SYSTEM_RAM, strlen(SYSTEM_RAM)) == 0)
+	} else if (strncmp(str, SYSTEM_RAM, strlen(SYSTEM_RAM)) == 0)
 		return mem_regions_alloc_and_add(&system_memory_rgns,
 						base, length, RANGE_RAM);
 	else if (strncmp(str, KERNEL_CODE, strlen(KERNEL_CODE)) == 0) {
-- 
2.41.0