Merge tag 'iommu-fixes-v5.3-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git...

[sfrench/cifs-2.6.git] / arch / x86 / boot / compressed / pgtable_64.c

diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c
index 5f2d03067ae57cdb95555fe423bdafc52bbec200..c8862696a47b949be25235531a39a65db94eb8ba 100644 (file)
--- 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 = bios_start;
+
                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;
        }