The patch titled
Subject: kasan, vmalloc: only tag normal vmalloc allocations
has been removed from the -mm tree. Its filename was
kasan-vmalloc-only-tag-normal-vmalloc-allocations.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
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@xxxxxxxxxx: pass KASAN_VMALLOC_PROT_NORMAL to kasan_unpoison_vmalloc()]
Link: https://lkml.kernel.org/r/9230ca3d3e40ffca041c133a524191fd71969a8d.1646233925.git.andreyknvl@xxxxxxxxxx
[andreyknvl@xxxxxxxxxx: support tagged vmalloc mappings]
Link: https://lkml.kernel.org/r/2f6605e3a358cf64d73a05710cb3da356886ad29.1646233925.git.andreyknvl@xxxxxxxxxx
[andreyknvl@xxxxxxxxxx: don't unintentionally disabled poisoning]
Link: https://lkml.kernel.org/r/de4587d6a719232e83c760113e46ed2d4d8da61e.1646757322.git.andreyknvl@xxxxxxxxxx
Link: https://lkml.kernel.org/r/fbfd9939a4dc375923c9a5c6b9e7ab05c26b8c6b.1643047180.git.andreyknvl@xxxxxxxxxx
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Acked-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Evgenii Stepanov <eugenis@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Peter Collingbourne <pcc@xxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/kasan.h | 7 +++--
kernel/scs.c | 12 ++++++---
mm/kasan/hw_tags.c | 7 +++++
mm/kasan/shadow.c | 8 ++++++
mm/vmalloc.c | 49 +++++++++++++++++++++++-----------------
5 files changed, 56 insertions(+), 27 deletions(-)
--- a/include/linux/kasan.h~kasan-vmalloc-only-tag-normal-vmalloc-allocations
+++ a/include/linux/kasan.h
@@ -28,9 +28,10 @@ struct kunit_kasan_expectation {
typedef unsigned int __bitwise kasan_vmalloc_flags_t;
-#define KASAN_VMALLOC_NONE 0x00u
-#define KASAN_VMALLOC_INIT 0x01u
-#define KASAN_VMALLOC_VM_ALLOC 0x02u
+#define KASAN_VMALLOC_NONE 0x00u
+#define KASAN_VMALLOC_INIT 0x01u
+#define KASAN_VMALLOC_VM_ALLOC 0x02u
+#define KASAN_VMALLOC_PROT_NORMAL 0x04u
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
--- a/kernel/scs.c~kasan-vmalloc-only-tag-normal-vmalloc-allocations
+++ a/kernel/scs.c
@@ -32,15 +32,19 @@ static void *__scs_alloc(int node)
for (i = 0; i < NR_CACHED_SCS; i++) {
s = this_cpu_xchg(scs_cache[i], NULL);
if (s) {
- kasan_unpoison_vmalloc(s, SCS_SIZE, KASAN_VMALLOC_NONE);
+ s = kasan_unpoison_vmalloc(s, SCS_SIZE,
+ KASAN_VMALLOC_PROT_NORMAL);
memset(s, 0, SCS_SIZE);
- return s;
+ goto out;
}
}
- return __vmalloc_node_range(SCS_SIZE, 1, VMALLOC_START, VMALLOC_END,
+ s = __vmalloc_node_range(SCS_SIZE, 1, VMALLOC_START, VMALLOC_END,
GFP_SCS, PAGE_KERNEL, 0, node,
__builtin_return_address(0));
+
+out:
+ return kasan_reset_tag(s);
}
void *scs_alloc(int node)
@@ -78,7 +82,7 @@ void scs_free(void *s)
if (this_cpu_cmpxchg(scs_cache[i], 0, s) == NULL)
return;
- kasan_unpoison_vmalloc(s, SCS_SIZE, KASAN_VMALLOC_NONE);
+ kasan_unpoison_vmalloc(s, SCS_SIZE, KASAN_VMALLOC_PROT_NORMAL);
vfree_atomic(s);
}
--- a/mm/kasan/hw_tags.c~kasan-vmalloc-only-tag-normal-vmalloc-allocations
+++ a/mm/kasan/hw_tags.c
@@ -247,6 +247,13 @@ void *__kasan_unpoison_vmalloc(const voi
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);
--- a/mm/kasan/shadow.c~kasan-vmalloc-only-tag-normal-vmalloc-allocations
+++ a/mm/kasan/shadow.c
@@ -488,6 +488,14 @@ void *__kasan_unpoison_vmalloc(const voi
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;
--- a/mm/vmalloc.c~kasan-vmalloc-only-tag-normal-vmalloc-allocations
+++ a/mm/vmalloc.c
@@ -2242,7 +2242,7 @@ void *vm_map_ram(struct page **pages, un
* With hardware tag-based KASAN, marking is skipped for
* non-VM_ALLOC mappings, see __kasan_unpoison_vmalloc().
*/
- mem = kasan_unpoison_vmalloc(mem, size, KASAN_VMALLOC_NONE);
+ mem = kasan_unpoison_vmalloc(mem, size, KASAN_VMALLOC_PROT_NORMAL);
return mem;
}
@@ -2481,7 +2481,7 @@ static struct vm_struct *__get_vm_area_n
*/
if (!(flags & VM_ALLOC))
area->addr = kasan_unpoison_vmalloc(area->addr, requested_size,
- KASAN_VMALLOC_NONE);
+ KASAN_VMALLOC_PROT_NORMAL);
return area;
}
@@ -3091,7 +3091,7 @@ void *__vmalloc_node_range(unsigned long
{
struct vm_struct *area;
void *ret;
- kasan_vmalloc_flags_t kasan_flags;
+ kasan_vmalloc_flags_t kasan_flags = KASAN_VMALLOC_NONE;
unsigned long real_size = size;
unsigned long real_align = align;
unsigned int shift = PAGE_SHIFT;
@@ -3144,21 +3144,28 @@ again:
goto fail;
}
- /* Prepare arguments for __vmalloc_area_node(). */
- if (kasan_hw_tags_enabled() &&
- pgprot_val(prot) == pgprot_val(PAGE_KERNEL)) {
- /*
- * Modify protection bits to allow tagging.
- * This must be done before mapping in __vmalloc_area_node().
- */
- prot = arch_vmap_pgprot_tagged(prot);
+ /*
+ * Prepare arguments for __vmalloc_area_node() and
+ * kasan_unpoison_vmalloc().
+ */
+ if (pgprot_val(prot) == pgprot_val(PAGE_KERNEL)) {
+ if (kasan_hw_tags_enabled()) {
+ /*
+ * Modify protection bits to allow tagging.
+ * This must be done before mapping.
+ */
+ prot = arch_vmap_pgprot_tagged(prot);
- /*
- * Skip page_alloc poisoning and zeroing for physical pages
- * backing VM_ALLOC mapping. Memory is instead poisoned and
- * zeroed by kasan_unpoison_vmalloc().
- */
- gfp_mask |= __GFP_SKIP_KASAN_UNPOISON | __GFP_SKIP_ZERO;
+ /*
+ * Skip page_alloc poisoning and zeroing for physical
+ * pages backing VM_ALLOC mapping. Memory is instead
+ * poisoned and zeroed by kasan_unpoison_vmalloc().
+ */
+ gfp_mask |= __GFP_SKIP_KASAN_UNPOISON | __GFP_SKIP_ZERO;
+ }
+
+ /* Take note that the mapping is PAGE_KERNEL. */
+ kasan_flags |= KASAN_VMALLOC_PROT_NORMAL;
}
/* Allocate physical pages and map them into vmalloc space. */
@@ -3172,10 +3179,13 @@ again:
* (except for the should_skip_init() check) to make sure that memory
* is initialized under the same conditions regardless of the enabled
* KASAN mode.
+ * Tag-based KASAN modes only assign tags to normal non-executable
+ * allocations, see __kasan_unpoison_vmalloc().
*/
- kasan_flags = KASAN_VMALLOC_VM_ALLOC;
+ kasan_flags |= KASAN_VMALLOC_VM_ALLOC;
if (!want_init_on_free() && want_init_on_alloc(gfp_mask))
kasan_flags |= KASAN_VMALLOC_INIT;
+ /* KASAN_VMALLOC_PROT_NORMAL already set if required. */
area->addr = kasan_unpoison_vmalloc(area->addr, real_size, kasan_flags);
/*
@@ -3881,8 +3891,7 @@ retry:
*/
for (area = 0; area < nr_vms; area++)
vms[area]->addr = kasan_unpoison_vmalloc(vms[area]->addr,
- vms[area]->size,
- KASAN_VMALLOC_NONE);
+ vms[area]->size, KASAN_VMALLOC_PROT_NORMAL);
kfree(vas);
return vms;
_
Patches currently in -mm which might be from andreyknvl@xxxxxxxxxx are
stacktrace-add-interface-based-on-shadow-call-stack.patch
arm64-scs-save-scs_sp-values-per-cpu-when-switching-stacks.patch
arm64-implement-stack_trace_save_shadow.patch
kasan-use-stack_trace_save_shadow.patch
