From 36e678741533d8e26bf9219dae5631f37a5998a3 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Sun, 18 Jun 2023 20:29:32 +0200
Subject: [PATCH] kernel: Make sure addresses allocated by mmap() are ALWAYS
 page-aligned

Fixes a kernel crash. Thanks a lot, sysfuzz!
---
 kernel/src/sys/mmap.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/src/sys/mmap.cpp b/kernel/src/sys/mmap.cpp
index 66c89fc4..f6516d20 100644
--- a/kernel/src/sys/mmap.cpp
+++ b/kernel/src/sys/mmap.cpp
@@ -41,9 +41,9 @@ Result<u64> sys_mmap(Registers*, SyscallArgs args)
     else
     {
         // FIXME: We should be more flexible if MAP_FIXED was not specified.
-        if (!TRY(current->vm_allocator->test_and_alloc_region((u64)addr, get_blocks_from_size(len, ARCH_PAGE_SIZE))))
+        address = align_down<ARCH_PAGE_SIZE>((u64)addr);
+        if (!TRY(current->vm_allocator->test_and_alloc_region(address, get_blocks_from_size(len, ARCH_PAGE_SIZE))))
             return err(ENOMEM);
-        address = (u64)addr;
     }
 
     int mmu_flags = MMU::User | MMU::NoExecute;