[tip: x86/urgent] x86/xen: Fix a potential problem in xen_e820_resolve_conflicts()

[tip-bot2 for Juergen Gross]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     5f8719945244dd65b5fa06195f4600db62581610
Gitweb:        https://git.kernel.org/tip/5f8719945244dd65b5fa06195f4600db62581610
Author:        Juergen Gross <jgross@xxxxxxxx>
AuthorDate:    Tue, 05 May 2026 10:06:53 +02:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Tue, 05 May 2026 10:17:00 +02:00

x86/xen: Fix a potential problem in xen_e820_resolve_conflicts()

When fixing a conflict in xen_e820_resolve_conflicts(), the loop over
the E820 map entries needs to be restarted, as the E820 map will have
been modified by the fix. Otherwise entries might be skipped by
accident.

Fixes: be35d91c8880 ("xen: tolerate ACPI NVS memory overlapping with Xen allocated memory")
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Link: https://patch.msgid.link/20260505080653.197775-1-jgross@xxxxxxxx
---
 arch/x86/xen/setup.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index ac8021c..bb95a05 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -695,17 +695,22 @@ static void __init xen_e820_resolve_conflicts(phys_addr_t start,
 		return;
 
 	end = start + size;
-	entry = xen_e820_table.entries;
+	mapcnt = 0;
 
-	for (mapcnt = 0; mapcnt < xen_e820_table.nr_entries; mapcnt++) {
+	while (mapcnt < xen_e820_table.nr_entries) {
+		entry = xen_e820_table.entries + mapcnt;
 		if (entry->addr >= end)
 			return;
 
 		if (entry->addr + entry->size > start &&
-		    entry->type == E820_TYPE_NVS)
+		    entry->type == E820_TYPE_NVS) {
 			xen_e820_swap_entry_with_ram(entry);
+			/* E820 map has been changed, restart loop! */
+			mapcnt = 0;
+			continue;
+		}
 
-		entry++;
+		mapcnt++;
 	}
 }