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author | Andrey Konovalov <andreyknvl@google.com> | 2022-09-06 00:05:45 +0300 |
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committer | Andrew Morton <akpm@linux-foundation.org> | 2022-10-04 00:03:01 +0300 |
commit | 7bc0584e5d2a687c0855a1b3dec9a6d6857d757b (patch) | |
tree | c08b7cb13e8ec5dd82a1aa82e9416aabc2bcee12 /mm/kasan/tags.c | |
parent | 59e6e098d1c156f7c449af903c3b48a5470f6120 (diff) | |
download | linux-7bc0584e5d2a687c0855a1b3dec9a6d6857d757b.tar.xz |
kasan: implement stack ring for tag-based modes
Implement storing stack depot handles for alloc/free stack traces for slab
objects for the tag-based KASAN modes in a ring buffer.
This ring buffer is referred to as the stack ring.
On each alloc/free of a slab object, the tagged address of the object and
the current stack trace are recorded in the stack ring.
On each bug report, if the accessed address belongs to a slab object, the
stack ring is scanned for matching entries. The newest entries are used
to print the alloc/free stack traces in the report: one entry for alloc
and one for free.
The number of entries in the stack ring is fixed in this patch, but one of
the following patches adds a command-line argument to control it.
[andreyknvl@google.com: initialize read-write lock in stack ring]
Link: https://lkml.kernel.org/r/576182d194e27531e8090bad809e4136953895f4.1663700262.git.andreyknvl@google.com
Link: https://lkml.kernel.org/r/692de14b6b6a1bc817fd55e4ad92fc1f83c1ab59.1662411799.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Peter Collingbourne <pcc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/kasan/tags.c')
-rw-r--r-- | mm/kasan/tags.c | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c index 39a0481e5228..a0524e037f49 100644 --- a/mm/kasan/tags.c +++ b/mm/kasan/tags.c @@ -6,6 +6,7 @@ * Copyright (c) 2020 Google, Inc. */ +#include <linux/atomic.h> #include <linux/init.h> #include <linux/kasan.h> #include <linux/kernel.h> @@ -16,11 +17,62 @@ #include <linux/types.h> #include "kasan.h" +#include "../slab.h" + +/* Non-zero, as initial pointer values are 0. */ +#define STACK_RING_BUSY_PTR ((void *)1) + +struct kasan_stack_ring stack_ring = { + .lock = __RW_LOCK_UNLOCKED(stack_ring.lock) +}; + +static void save_stack_info(struct kmem_cache *cache, void *object, + gfp_t gfp_flags, bool is_free) +{ + unsigned long flags; + depot_stack_handle_t stack; + u64 pos; + struct kasan_stack_ring_entry *entry; + void *old_ptr; + + stack = kasan_save_stack(gfp_flags, true); + + /* + * Prevent save_stack_info() from modifying stack ring + * when kasan_complete_mode_report_info() is walking it. + */ + read_lock_irqsave(&stack_ring.lock, flags); + +next: + pos = atomic64_fetch_add(1, &stack_ring.pos); + entry = &stack_ring.entries[pos % KASAN_STACK_RING_SIZE]; + + /* Detect stack ring entry slots that are being written to. */ + old_ptr = READ_ONCE(entry->ptr); + if (old_ptr == STACK_RING_BUSY_PTR) + goto next; /* Busy slot. */ + if (!try_cmpxchg(&entry->ptr, &old_ptr, STACK_RING_BUSY_PTR)) + goto next; /* Busy slot. */ + + WRITE_ONCE(entry->size, cache->object_size); + WRITE_ONCE(entry->pid, current->pid); + WRITE_ONCE(entry->stack, stack); + WRITE_ONCE(entry->is_free, is_free); + + /* + * Paired with smp_load_acquire() in kasan_complete_mode_report_info(). + */ + smp_store_release(&entry->ptr, (s64)object); + + read_unlock_irqrestore(&stack_ring.lock, flags); +} void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags) { + save_stack_info(cache, object, flags, false); } void kasan_save_free_info(struct kmem_cache *cache, void *object) { + save_stack_info(cache, object, GFP_NOWAIT, true); } |