From 0fe9a448a029a11d7211fcc2ebe9023d7fd31792 Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Mon, 14 Oct 2019 14:11:44 -0700 Subject: mm, page_owner: decouple freeing stack trace from debug_pagealloc 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 [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 Reviewed-by: Qian Cai Suggested-by: Dmitry Vyukov Suggested-by: Walter Wu Suggested-by: Andrey Ryabinin Suggested-by: Kirill A. Shutemov Suggested-by: Qian Cai Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/dev-tools/kasan.rst | 3 +++ 1 file changed, 3 insertions(+) (limited to 'Documentation') 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: -- cgit