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Wed, 19 May 2021 18:35:43 -0700 (PDT) Received: from smtp.gmail.com ([2620:15c:202:201:200b:db75:4e6c:8b96]) by smtp.gmail.com with ESMTPSA id m20sm5097368pjq.40.2021.05.19.18.35.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 May 2021 18:35:43 -0700 (PDT) From: Stephen Boyd To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , linux-mm@kvack.org Subject: [PATCH 2/3] slub: Print raw pointer addresses when debugging Date: Wed, 19 May 2021 18:35:38 -0700 Message-Id: <20210520013539.3733631-3-swboyd@chromium.org> X-Mailer: git-send-email 2.31.1.751.gd2f1c929bd-goog In-Reply-To: <20210520013539.3733631-1-swboyd@chromium.org> References: <20210520013539.3733631-1-swboyd@chromium.org> MIME-Version: 1.0 X-Rspamd-Queue-Id: F2EEAA0003B2 Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=fcRCAtiZ; spf=pass (imf23.hostedemail.com: domain of swboyd@chromium.org designates 209.85.215.178 as permitted sender) smtp.mailfrom=swboyd@chromium.org; dmarc=pass (policy=none) header.from=chromium.org X-Rspamd-Server: rspam04 X-Stat-Signature: wh6587s4nzhyajaopz7fbegqa5wpjqxo X-HE-Tag: 1621474542-105445 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Obscuring the pointers that slub shows when debugging makes for some confusing slub debug messages: Padding overwritten. 0x0000000079f0674a-0x000000000d4dce17 Those addresses are hashed for kernel security reasons. If we're trying to be secure with slub_debug on the commandline we have some big problems given that we dump whole chunks of kernel memory to the kernel logs. Let's use %px here and dump buffers with the actual address for the buffer instead of the hashed version so that the logs are meaningful. This also helps if a kernel address is in some slub debug report so we can figure out that the object is referencing itself. Signed-off-by: Stephen Boyd --- mm/slub.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index feda53ae62ba..87eeeed1f369 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -549,7 +549,7 @@ static void print_section(char *level, char *text, u8 *addr, unsigned int length) { metadata_access_enable(); - print_hex_dump(level, kasan_reset_tag(text), DUMP_PREFIX_ADDRESS, + print_hex_dump(level, kasan_reset_tag(text), DUMP_PREFIX_RAW_ADDRESS, 16, 1, addr, length, 1); metadata_access_disable(); } @@ -650,7 +650,7 @@ void print_tracking(struct kmem_cache *s, void *object) static void print_page_info(struct page *page) { - pr_err("Slab 0x%p objects=%u used=%u fp=0x%p flags=%#lx(%pGp)\n", + pr_err("Slab 0x%px objects=%u used=%u fp=0x%px flags=%#lx(%pGp)\n", page, page->objects, page->inuse, page->freelist, page->flags, &page->flags); @@ -707,7 +707,7 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p) print_page_info(page); - pr_err("Object 0x%p @offset=%tu fp=0x%p\n\n", + pr_err("Object 0x%px @offset=%tu fp=0x%px\n\n", p, p - addr, get_freepointer(s, p)); if (s->flags & SLAB_RED_ZONE) @@ -777,7 +777,7 @@ static void init_object(struct kmem_cache *s, void *object, u8 val) static void restore_bytes(struct kmem_cache *s, char *message, u8 data, void *from, void *to) { - slab_fix(s, "Restoring 0x%p-0x%p=0x%x\n", from, to - 1, data); + slab_fix(s, "Restoring 0x%px-0x%px=0x%x\n", from, to - 1, data); memset(from, data, to - from); } @@ -800,7 +800,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page, end--; slab_bug(s, "%s overwritten", what); - pr_err("0x%p-0x%p @offset=%tu. First byte 0x%x instead of 0x%x\n", + pr_err("0x%px-0x%px @offset=%tu. First byte 0x%x instead of 0x%x\n", fault, end - 1, fault - addr, fault[0], value); print_trailer(s, page, object); @@ -893,7 +893,7 @@ static int slab_pad_check(struct kmem_cache *s, struct page *page) while (end > fault && end[-1] == POISON_INUSE) end--; - slab_err(s, page, "Padding overwritten. 0x%p-0x%p @offset=%tu", + slab_err(s, page, "Padding overwritten. 0x%px-0x%px @offset=%tu", fault, end - 1, fault - start); print_section(KERN_ERR, "Padding ", pad, remainder); @@ -1041,7 +1041,7 @@ static void trace(struct kmem_cache *s, struct page *page, void *object, int alloc) { if (s->flags & SLAB_TRACE) { - pr_info("TRACE %s %s 0x%p inuse=%d fp=0x%p\n", + pr_info("TRACE %s %s 0x%px inuse=%d fp=0x%px\n", s->name, alloc ? "alloc" : "free", object, page->inuse, @@ -1186,7 +1186,7 @@ static inline int free_consistency_checks(struct kmem_cache *s, struct page *page, void *object, unsigned long addr) { if (!check_valid_pointer(s, page, object)) { - slab_err(s, page, "Invalid object pointer 0x%p", object); + slab_err(s, page, "Invalid object pointer 0x%px", object); return 0; } @@ -1200,10 +1200,10 @@ static inline int free_consistency_checks(struct kmem_cache *s, if (unlikely(s != page->slab_cache)) { if (!PageSlab(page)) { - slab_err(s, page, "Attempt to free object(0x%p) outside of slab", + slab_err(s, page, "Attempt to free object(0x%px) outside of slab", object); } else if (!page->slab_cache) { - pr_err("SLUB : no slab for object 0x%p.\n", + pr_err("SLUB : no slab for object 0x%px.\n", object); dump_stack(); } else @@ -1263,7 +1263,7 @@ static noinline int free_debug_processing( slab_unlock(page); spin_unlock_irqrestore(&n->list_lock, flags); if (!ret) - slab_fix(s, "Object at 0x%p not freed", object); + slab_fix(s, "Object at 0x%px not freed", object); return ret; } @@ -3908,7 +3908,7 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page, for_each_object(p, s, addr, page->objects) { if (!test_bit(__obj_to_index(s, addr, p), map)) { - pr_err("Object 0x%p @offset=%tu\n", p, p - addr); + pr_err("Object 0x%px @offset=%tu\n", p, p - addr); print_tracking(s, p); } }