On Tue, Aug 20 2024 at 15:16, kernel test robot wrote:
> commit: dfb3911c3692e45b027f13c7dca3230921533953 ("x86/kaslr: Expose and use the end of the physical memory address space")
>
> [ 0.010309][ T0] ------------[ cut here ]------------
> [ 0.011020][ T0] kernel BUG at arch/x86/mm/physaddr.c:28!
> [ 0.026951][ T0] ? __phys_addr (ld-temp.o:?)
> [ 0.027298][ T0] ? kernel_randomize_memory (ld-temp.o:?)
Sigh. I'm a moron. This obviously needs the fix below.
The end of the region is start + size - 1. So there are two bugs:
1) It needs to be done before jumping forward to the next PUD.
2) If the direct map covers the full address space, then
__pa(vaddr) is wrong because that's the next PUD already.
I'll amend the commit and force push it. Thankfully I did not have time
on sunday to send it to Linus :)
Thanks,
tglx
---
diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
index 0f2a3a4a1078..230f1dee4f09 100644
--- a/arch/x86/mm/kaslr.c
+++ b/arch/x86/mm/kaslr.c
@@ -141,19 +141,19 @@ void __init kernel_randomize_memory(void)
vaddr += entropy;
*kaslr_regions[i].base = vaddr;
- /*
- * Jump the region and add a minimum padding based on
- * randomization alignment.
- */
+ /* Calculate the end of the region */
vaddr += get_padding(&kaslr_regions[i]);
- vaddr = round_up(vaddr + 1, PUD_SIZE);
-
/*
* KASLR trims the maximum possible size of the
* direct-map. Update the physmem_end boundary.
+ * No rounding required as the region starts
+ * PUD aligned and size is in units of TB.
*/
if (kaslr_regions[i].end)
- *kaslr_regions[i].end = __pa(vaddr) - 1;
+ *kaslr_regions[i].end = __pa_nodebug(vaddr - 1);
+
+ /* Add a minimum padding based on randomization alignment. */
+ vaddr = round_up(vaddr + 1, PUD_SIZE);
remain_entropy -= entropy;
}
}
