[PATCH v2 2/3] mm/usercopy: Detect vmalloc overruns
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Date: 2021-10-06 12:45:17
Subsystem:
kernel hardening (not covered by other areas), memory management, the rest · Maintainers:
Kees Cook, Andrew Morton, Linus Torvalds
If you have a vmalloc() allocation, or an address from calling vmap(), you cannot overrun the vm_area which describes it, regardless of the size of the underlying allocation. This probably doesn't do much for security because vmalloc comes with guard pages these days, but it prevents usercopy aborts when copying to a vmap() of smaller pages. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Acked-by: Kees Cook <redacted> --- mm/usercopy.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/mm/usercopy.c b/mm/usercopy.c
index 8c039302465f..63476e1506e0 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c@@ -17,6 +17,7 @@ #include <linux/sched/task.h> #include <linux/sched/task_stack.h> #include <linux/thread_info.h> +#include <linux/vmalloc.h> #include <linux/atomic.h> #include <linux/jump_label.h> #include <asm/sections.h>
@@ -237,6 +238,21 @@ static inline void check_heap_object(const void *ptr, unsigned long n, return; } + if (is_vmalloc_addr(ptr)) { + struct vm_struct *vm = find_vm_area(ptr); + unsigned long offset; + + if (!vm) { + usercopy_abort("vmalloc", "no area", to_user, 0, n); + return; + } + + offset = ptr - vm->addr; + if (offset + n > vm->size) + usercopy_abort("vmalloc", NULL, to_user, offset, n); + return; + } + page = virt_to_head_page(ptr); if (PageSlab(page)) {
--
2.32.0