diff mbox series

[2/4] mm/usercopy: Detect vmalloc overruns

Message ID 20220110231530.665970-3-willy@infradead.org (mailing list archive)
State New
Headers show
Series Assorted improvements to usercopy | expand

Commit Message

Matthew Wilcox Jan. 10, 2022, 11:15 p.m. UTC 
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 <keescook@chromium.org>
---
 mm/usercopy.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
diff mbox series

Patch

diff --git a/mm/usercopy.c b/mm/usercopy.c
index 2d13bc3bd83b..dcf71b7e3098 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>
@@ -238,6 +239,21 @@  static inline void check_heap_object(const void *ptr, unsigned long n,
 		return;
 	}
 
+	if (is_vmalloc_addr(ptr)) {
+		struct vm_struct *area = find_vm_area(ptr);
+		unsigned long offset;
+
+		if (!area) {
+			usercopy_abort("vmalloc", "no area", to_user, 0, n);
+			return;
+		}
+
+		offset = ptr - area->addr;
+		if (offset + n > get_vm_area_size(area))
+			usercopy_abort("vmalloc", NULL, to_user, offset, n);
+		return;
+	}
+
 	folio = virt_to_folio(ptr);
 
 	if (folio_test_slab(folio)) {