From f6e39794f4b6da7ca9b77f2f9ad11fd6f0ac83e5 Mon Sep 17 00:00:00 2001 From: Andrey Konovalov Date: Thu, 24 Mar 2022 18:11:35 -0700 Subject: kasan, vmalloc: only tag normal vmalloc allocations The kernel can use to allocate executable memory. The only supported way to do that is via __vmalloc_node_range() with the executable bit set in the prot argument. (vmap() resets the bit via pgprot_nx()). Once tag-based KASAN modes start tagging vmalloc allocations, executing code from such allocations will lead to the PC register getting a tag, which is not tolerated by the kernel. Only tag the allocations for normal kernel pages. [andreyknvl@google.com: pass KASAN_VMALLOC_PROT_NORMAL to kasan_unpoison_vmalloc()] Link: https://lkml.kernel.org/r/9230ca3d3e40ffca041c133a524191fd71969a8d.1646233925.git.andreyknvl@google.com [andreyknvl@google.com: support tagged vmalloc mappings] Link: https://lkml.kernel.org/r/2f6605e3a358cf64d73a05710cb3da356886ad29.1646233925.git.andreyknvl@google.com [andreyknvl@google.com: don't unintentionally disabled poisoning] Link: https://lkml.kernel.org/r/de4587d6a719232e83c760113e46ed2d4d8da61e.1646757322.git.andreyknvl@google.com Link: https://lkml.kernel.org/r/fbfd9939a4dc375923c9a5c6b9e7ab05c26b8c6b.1643047180.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Acked-by: Marco Elver Cc: Alexander Potapenko Cc: Andrey Ryabinin Cc: Catalin Marinas Cc: Dmitry Vyukov Cc: Evgenii Stepanov Cc: Mark Rutland Cc: Peter Collingbourne Cc: Vincenzo Frascino Cc: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/kasan/hw_tags.c | 7 +++++++ mm/kasan/shadow.c | 8 ++++++++ 2 files changed, 15 insertions(+) (limited to 'mm/kasan') diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c index 21104fd51872..2e9378a4f07f 100644 --- a/mm/kasan/hw_tags.c +++ b/mm/kasan/hw_tags.c @@ -247,6 +247,13 @@ void *__kasan_unpoison_vmalloc(const void *start, unsigned long size, if (!(flags & KASAN_VMALLOC_VM_ALLOC)) return (void *)start; + /* + * Don't tag executable memory. + * The kernel doesn't tolerate having the PC register tagged. + */ + if (!(flags & KASAN_VMALLOC_PROT_NORMAL)) + return (void *)start; + tag = kasan_random_tag(); start = set_tag(start, tag); diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c index b958babc8fed..a4f07de21771 100644 --- a/mm/kasan/shadow.c +++ b/mm/kasan/shadow.c @@ -488,6 +488,14 @@ void *__kasan_unpoison_vmalloc(const void *start, unsigned long size, if (!is_vmalloc_or_module_addr(start)) return (void *)start; + /* + * Don't tag executable memory with the tag-based mode. + * The kernel doesn't tolerate having the PC register tagged. + */ + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS) && + !(flags & KASAN_VMALLOC_PROT_NORMAL)) + return (void *)start; + start = set_tag(start, kasan_random_tag()); kasan_unpoison(start, size, false); return (void *)start; -- cgit v1.2.3