| Message ID | 20191007091808.7096-3-vbabka@suse.cz (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | followups to debug_pagealloc improvements through page_owner | expand |
> On Oct 7, 2019, at 5:18 AM, Vlastimil Babka <vbabka@suse.cz> wrote: > > The commit 8974558f49a6 ("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 > > 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: Vlastimil Babka <vbabka@suse.cz> > --- > Documentation/dev-tools/kasan.rst | 3 +++ > mm/page_owner.c | 28 +++++++--------------------- > 2 files changed, 10 insertions(+), 21 deletions(-) The diffstat looks nice! Reviewed-by: Qian Cai <cai@lca.pw> > > diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst > index b72d07d70239..525296121d89 100644 > --- a/Documentation/dev-tools/kasan.rst > +++ b/Documentation/dev-tools/kasan.rst > @@ -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: > > diff --git a/mm/page_owner.c b/mm/page_owner.c > index d3cf5d336ccf..de1916ac3e24 100644 > --- a/mm/page_owner.c > +++ b/mm/page_owner.c > @@ -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", > -- > 2.23.0
diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst index b72d07d70239..525296121d89 100644 --- a/Documentation/dev-tools/kasan.rst +++ b/Documentation/dev-tools/kasan.rst @@ -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: diff --git a/mm/page_owner.c b/mm/page_owner.c index d3cf5d336ccf..de1916ac3e24 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -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",
The commit 8974558f49a6 ("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 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: Vlastimil Babka <vbabka@suse.cz> --- Documentation/dev-tools/kasan.rst | 3 +++ mm/page_owner.c | 28 +++++++--------------------- 2 files changed, 10 insertions(+), 21 deletions(-)