[050/114] kasan, vmalloc: reset tags in vmalloc functions

Commit Message

Andrew Morton March 25, 2022, 1:11 a.m. UTC

From: Andrey Konovalov <[e-mail]>
Subject: kasan, vmalloc: reset tags in vmalloc functions

In preparation for adding vmalloc support to SW/HW_TAGS KASAN, reset
pointer tags in functions that use pointer values in range checks.

vread() is a special case here.  Despite the untagging of the addr pointer
in its prologue, the accesses performed by vread() are checked.

Instead of accessing the virtual mappings though addr directly, vread()
recovers the physical address via page_address(vmalloc_to_page()) and
acceses that.  And as page_address() recovers the pointer tag, the
accesses get checked.

Link: https://lkml.kernel.org/r/04[e-mail]
Signed-off-by: Andrey Konovalov <[e-mail]>
Acked-by: Marco Elver <[e-mail]>
Cc: Alexander Potapenko <[e-mail]>
Cc: Andrey Ryabinin <[e-mail]>
Cc: Catalin Marinas <[e-mail]>
Cc: Dmitry Vyukov <[e-mail]>
Cc: Evgenii Stepanov <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Peter Collingbourne <[e-mail]>
Cc: Vincenzo Frascino <[e-mail]>
Cc: Will Deacon <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/vmalloc.c |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

Patch

--- a/mm/vmalloc.c~kasan-vmalloc-reset-tags-in-vmalloc-functions
+++ a/mm/vmalloc.c
@@ -74,7 +74,7 @@  static const bool vmap_allow_huge = fals
 
 bool is_vmalloc_addr(const void *x)
 {
-	unsigned long addr = (unsigned long)x;
+	unsigned long addr = (unsigned long)kasan_reset_tag(x);
 
 	return addr >= VMALLOC_START && addr < VMALLOC_END;
 }
@@ -631,7 +631,7 @@  int is_vmalloc_or_module_addr(const void
 	 * just put it in the vmalloc space.
 	 */
 #if defined(CONFIG_MODULES) && defined(MODULES_VADDR)
-	unsigned long addr = (unsigned long)x;
+	unsigned long addr = (unsigned long)kasan_reset_tag(x);
 	if (addr >= MODULES_VADDR && addr < MODULES_END)
 		return 1;
 #endif
@@ -795,6 +795,8 @@  static struct vmap_area *find_vmap_area_
 	struct vmap_area *va = NULL;
 	struct rb_node *n = vmap_area_root.rb_node;
 
+	addr = (unsigned long)kasan_reset_tag((void *)addr);
+
 	while (n) {
 		struct vmap_area *tmp;
 
@@ -816,6 +818,8 @@  static struct vmap_area *__find_vmap_are
 {
 	struct rb_node *n = vmap_area_root.rb_node;
 
+	addr = (unsigned long)kasan_reset_tag((void *)addr);
+
 	while (n) {
 		struct vmap_area *va;
 
@@ -2166,7 +2170,7 @@  EXPORT_SYMBOL_GPL(vm_unmap_aliases);
 void vm_unmap_ram(const void *mem, unsigned int count)
 {
 	unsigned long size = (unsigned long)count << PAGE_SHIFT;
-	unsigned long addr = (unsigned long)mem;
+	unsigned long addr = (unsigned long)kasan_reset_tag(mem);
 	struct vmap_area *va;
 
 	might_sleep();
@@ -3424,6 +3428,8 @@  long vread(char *buf, char *addr, unsign
 	unsigned long buflen = count;
 	unsigned long n;
 
+	addr = kasan_reset_tag(addr);
+
 	/* Don't allow overflow */
 	if ((unsigned long) addr + count < count)
 		count = -(unsigned long) addr;