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mm, page_owner: decouple freeing stack trace from debug_pagealloc

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Commit 8974558f49 ("mm, page_owner, debug_pagealloc: save and dump
freeing stack trace") enhanced page_owner to also store freeing stack
trace, when debug_pagealloc is also enabled.  KASAN would also like to
do this [1] to improve error reports to debug e.g. UAF issues.

Kirill has suggested that the freeing stack trace saving should be also
possible to be enabled separately from KASAN or debug_pagealloc, i.e.
with an extra boot option.  Qian argued that we have enough options
already, and avoiding the extra overhead is not worth the complications
in the case of a debugging option.  Kirill noted that the extra stack
handle in struct page_owner requires 0.1% of memory.

This patch therefore enables free stack saving whenever page_owner is
enabled, regardless of whether debug_pagealloc or KASAN is also enabled.
KASAN kernels booted with page_owner=on will thus benefit from the
improved error reports.

[1] https://bugzilla.kernel.org/show_bug.cgi?id=203967

[vbabka@suse.cz: v3]
  Link: http://lkml.kernel.org/r/20191007091808.7096-3-vbabka@suse.cz
Link: http://lkml.kernel.org/r/20190930122916.14969-3-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Qian Cai <cai@lca.pw>
Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Suggested-by: Walter Wu <walter-zh.wu@mediatek.com>
Suggested-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Suggested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Suggested-by: Qian Cai <cai@lca.pw>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vlastimil Babka 2019-10-14 14:11:44 -07:00 committed by Linus Torvalds
parent 5556cfe8d9
commit 0fe9a448a0
2 changed files with 10 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
Documentation/dev-tools/kasan.rst
View File

@ -41,6 +41,9 @@ smaller binary while the latter is 1.1 - 2 times faster.
Both KASAN modes work with both SLUB and SLAB memory allocators.
For better bug detection and nicer reporting, enable CONFIG_STACKTRACE.
To augment reports with last allocation and freeing stack of the physical page,
it is recommended to enable also CONFIG_PAGE_OWNER and boot with page_owner=on.
To disable instrumentation for specific files or directories, add a line
similar to the following to the respective kernel Makefile:

28
mm/page_owner.c
View File

@ -24,12 +24,10 @@ struct page_owner {
short last_migrate_reason;
gfp_t gfp_mask;
depot_stack_handle_t handle;
#ifdef CONFIG_DEBUG_PAGEALLOC
depot_stack_handle_t free_handle;
#endif
};
static bool page_owner_disabled = true;
static bool page_owner_enabled = false;
DEFINE_STATIC_KEY_FALSE(page_owner_inited);
static depot_stack_handle_t dummy_handle;
@ -44,7 +42,7 @@ static int __init early_page_owner_param(char *buf)
return -EINVAL;
if (strcmp(buf, "on") == 0)
page_owner_disabled = false;
page_owner_enabled = true;
return 0;
}
@ -52,10 +50,7 @@ early_param("page_owner", early_page_owner_param);
static bool need_page_owner(void)
{
if (page_owner_disabled)
return false;
return true;
return page_owner_enabled;
}
static __always_inline depot_stack_handle_t create_dummy_stack(void)
@ -84,7 +79,7 @@ static noinline void register_early_stack(void)
static void init_page_owner(void)
{
if (page_owner_disabled)
if (!page_owner_enabled)
return;
register_dummy_stack();
@ -148,25 +143,18 @@ void __reset_page_owner(struct page *page, unsigned int order)
{
int i;
struct page_ext *page_ext;
#ifdef CONFIG_DEBUG_PAGEALLOC
depot_stack_handle_t handle = 0;
struct page_owner *page_owner;
if (debug_pagealloc_enabled())
handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
#endif
handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
page_ext = lookup_page_ext(page);
if (unlikely(!page_ext))
return;
for (i = 0; i < (1 << order); i++) {
__clear_bit(PAGE_EXT_OWNER_ACTIVE, &page_ext->flags);
#ifdef CONFIG_DEBUG_PAGEALLOC
if (debug_pagealloc_enabled()) {
page_owner = get_page_owner(page_ext);
page_owner->free_handle = handle;
}
#endif
page_owner = get_page_owner(page_ext);
page_owner->free_handle = handle;
page_ext = page_ext_next(page_ext);
}
}
@ -450,7 +438,6 @@ void __dump_page_owner(struct page *page)
stack_trace_print(entries, nr_entries, 0);
}
#ifdef CONFIG_DEBUG_PAGEALLOC
handle = READ_ONCE(page_owner->free_handle);
if (!handle) {
pr_alert("page_owner free stack trace missing\n");
@ -459,7 +446,6 @@ void __dump_page_owner(struct page *page)
pr_alert("page last free stack trace:\n");
stack_trace_print(entries, nr_entries, 0);
}
#endif
if (page_owner->last_migrate_reason != -1)
pr_alert("page has been migrated, last migrate reason: %s\n",