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-rw-r--r--arch/x86/boot/compressed/pgtable_64.c13
1 files changed, 10 insertions, 3 deletions
diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c
index 5f2d03067ae5..2faddeb0398a 100644
--- a/arch/x86/boot/compressed/pgtable_64.c
+++ b/arch/x86/boot/compressed/pgtable_64.c
@@ -72,6 +72,8 @@ static unsigned long find_trampoline_placement(void)
/* Find the first usable memory region under bios_start. */
for (i = boot_params->e820_entries - 1; i >= 0; i--) {
+ unsigned long new;
+
entry = &boot_params->e820_table[i];
/* Skip all entries above bios_start. */
@@ -84,15 +86,20 @@ static unsigned long find_trampoline_placement(void)
/* Adjust bios_start to the end of the entry if needed. */
if (bios_start > entry->addr + entry->size)
- bios_start = entry->addr + entry->size;
+ new = entry->addr + entry->size;
/* Keep bios_start page-aligned. */
- bios_start = round_down(bios_start, PAGE_SIZE);
+ new = round_down(new, PAGE_SIZE);
/* Skip the entry if it's too small. */
- if (bios_start - TRAMPOLINE_32BIT_SIZE < entry->addr)
+ if (new - TRAMPOLINE_32BIT_SIZE < entry->addr)
continue;
+ /* Protect against underflow. */
+ if (new - TRAMPOLINE_32BIT_SIZE > bios_start)
+ break;
+
+ bios_start = new;
break;
}