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[209.85.220.73]) by mx.google.com with SMTPS id 4sor4297673ots.99.2019.05.17.06.12.37 for (Google Transport Security); Fri, 17 May 2019 06:12:37 -0700 (PDT) Received-SPF: pass (google.com: domain of 3rbpexaukcbqy5fyb08805y.w86527eh-664fuw4.8b0@flex--elver.bounces.google.com designates 209.85.220.73 as permitted sender) client-ip=209.85.220.73; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=QISLHjwa; spf=pass (google.com: domain of 3rbpexaukcbqy5fyb08805y.w86527eh-664fuw4.8b0@flex--elver.bounces.google.com designates 209.85.220.73 as permitted sender) smtp.mailfrom=3RbPeXAUKCBQy5FyB08805y.w86527EH-664Fuw4.8B0@flex--elver.bounces.google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=FJs+O5o+cz5HCB5KlHNqWYoyNOZwk4659YdHbrsYlV8=; b=QISLHjwatyyS68LYxu91gfHOGzQZkApgwV9mJCFI2+RWppkrWl5mmmoYiRBI29wN1I uyOsslA27pzcBpqGEwQ6sWUys8fIjXCVlf29bhf3n+LidYegLvtgPa2YvKFvOwaT72I9 Hq840HxLmkBAUD61Jlm6ud0G+pc9jJi/oNgB74UhaXMiyrcxNIlenwLyGKBC3JFjWYY2 joOK7FiIbMpz4pd+YfikGAnZMNyopEgOVy0D9mFONqOaiFKWsLbbRR93udxpZzczyMXX uPh4kunT6noNrJYvnRdozUC0MUS1xDN3RQo86J2HGbtZ3vncn8AtsSc3/ABUf5UbEAZL 4o7Q== X-Google-Smtp-Source: APXvYqxmOCq/WWsSZJAMIRC2Pm/Zl7/sWdlJ9DsC/yZBgEQ30AhwQnCY8jEe8fPbKfuPtPxzZLyGdrUOaQ== X-Received: by 2002:a9d:400d:: with SMTP id m13mr14229666ote.100.1558098757436; Fri, 17 May 2019 06:12:37 -0700 (PDT) Date: Fri, 17 May 2019 15:10:46 +0200 Message-Id: <20190517131046.164100-1-elver@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.21.0.1020.gf2820cf01a-goog Subject: [PATCH] mm/kasan: Print frame description for stack bugs From: Marco Elver To: aryabinin@virtuozzo.com, dvyukov@google.com, glider@google.com, andreyknvl@google.com, akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kasan-dev@googlegroups.com, Marco Elver Content-Type: text/plain; charset="UTF-8" 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: This adds support for printing stack frame description on invalid stack accesses. The frame description is embedded by the compiler, which is parsed and then pretty-printed. Currently, we can only print the stack frame info for accesses to the task's own stack, but not accesses to other tasks' stacks. Example of what it looks like: [ 17.924050] page dumped because: kasan: bad access detected [ 17.924908] [ 17.925153] addr ffff8880673ef98a is located in stack of task insmod/2008 at offset 106 in frame: [ 17.926542] kasan_stack_oob+0x0/0xf5 [test_kasan] [ 17.927932] [ 17.928206] this frame has 2 objects: [ 17.928783] [32, 36) 'i' [ 17.928784] [96, 106) 'stack_array' [ 17.929216] [ 17.930031] Memory state around the buggy address: Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=198435 Signed-off-by: Marco Elver --- Change-Id: I4836cde103052991ac8871796a45b4c977c9e2e7 --- mm/kasan/kasan.h | 5 ++ mm/kasan/report.c | 160 ++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 165 insertions(+) diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index 3ce956efa0cb..1979db4763e2 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -43,6 +43,11 @@ #define KASAN_ALLOCA_REDZONE_SIZE 32 +/* + * Stack frame marker (compiler ABI). + */ +#define KASAN_CURRENT_STACK_FRAME_MAGIC 0x41B58AB3 + /* Don't break randconfig/all*config builds */ #ifndef KASAN_ABI_VERSION #define KASAN_ABI_VERSION 1 diff --git a/mm/kasan/report.c b/mm/kasan/report.c index 03a443579386..c6ad8462c0dc 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -28,6 +28,7 @@ #include #include #include +#include #include @@ -181,6 +182,163 @@ static inline bool init_task_stack_addr(const void *addr) sizeof(init_thread_union.stack)); } +static bool __must_check tokenize_frame_descr(const char **frame_descr, + char *token, size_t max_tok_len, + unsigned long *value) +{ + const char *sep = strchr(*frame_descr, ' '); + const ptrdiff_t tok_len = sep - *frame_descr; + + if (sep == NULL) + sep = *frame_descr + strlen(*frame_descr); + + if (token != NULL) { + if (tok_len + 1 > max_tok_len) { + pr_err("KASAN internal error: frame description too long: %s\n", + *frame_descr); + return false; + } + /* Copy token (+ 1 byte for '\0'). */ + strlcpy(token, *frame_descr, tok_len + 1); + } + /* Advance frame_descr past separator. */ + *frame_descr = sep + 1; + + if (value != NULL && kstrtoul(token, 10, value)) { + pr_err("KASAN internal error: not a valid number: %s\n", token); + return false; + } + + return true; +} + +static void print_decoded_frame_descr(const char *frame_descr) +{ + /* + * We need to parse the following string: + * "n alloc_1 alloc_2 ... alloc_n" + * where alloc_i looks like + * "offset size len name" + * or "offset size len name:line". + */ + + char token[64]; + unsigned long num_objects; + + if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), + &num_objects)) + return; + + pr_err("\n"); + pr_err("this frame has %zu %s:\n", num_objects, + num_objects == 1 ? "object" : "objects"); + + while (num_objects--) { + unsigned long offset; + unsigned long size; + + /* access offset */ + if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), + &offset)) + return; + /* access size */ + if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), + &size)) + return; + /* name length (unused) */ + if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL)) + return; + /* object name */ + if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), + NULL)) + return; + + /* Strip line number, if it exists. */ + strreplace(token, ':', '\0'); + + /* Finally, print object information. */ + pr_err(" [%zu, %zu) '%s'", offset, offset + size, token); + } +} + +static bool __must_check get_address_stack_frame_info(const void *addr, + size_t *offset, + const char **frame_descr, + const void **frame_pc) +{ + size_t aligned_addr; + size_t mem_ptr; + const u8 *shadow_bottom; + const u8 *shadow_ptr; + const size_t *frame; + + /* + * NOTE: We currently only support printing frame information for + * accesses to the task's own stack. + */ + if (!object_is_on_stack(addr)) + return false; + + aligned_addr = round_down((size_t)addr, sizeof(long)); + mem_ptr = round_down(aligned_addr, KASAN_SHADOW_SCALE_SIZE); + shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr); + shadow_bottom = kasan_mem_to_shadow(end_of_stack(current)); + + while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) { + shadow_ptr--; + mem_ptr -= KASAN_SHADOW_SCALE_SIZE; + } + + while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) { + shadow_ptr--; + mem_ptr -= KASAN_SHADOW_SCALE_SIZE; + } + + if (shadow_ptr < shadow_bottom) + return false; + + frame = (const size_t *)(mem_ptr + KASAN_SHADOW_SCALE_SIZE); + if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) { + pr_err("KASAN internal error: frame info validation failed; invalid marker: %zu\n", + frame[0]); + return false; + } + + *offset = (size_t)addr - (size_t)frame; + *frame_descr = (const char *)frame[1]; + *frame_pc = (void *)frame[2]; + + return true; +} + +static void print_address_stack_frame(const void *addr) +{ + size_t offset; + const char *frame_descr; + const void *frame_pc; + + if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) + return; + + if (!get_address_stack_frame_info(addr, &offset, &frame_descr, + &frame_pc)) + return; + + /* + * get_address_stack_frame_info only returns true if the given addr is + * on the current task's stack. + */ + pr_err("\n"); + pr_err("addr %px is located in stack of task %s/%d at offset %zu in frame:\n", + addr, current->comm, task_pid_nr(current), offset); + pr_err(" %pS\n", frame_pc); + + if (!frame_descr) + return; + + print_decoded_frame_descr(frame_descr); +} + static void print_address_description(void *addr) { struct page *page = addr_to_page(addr); @@ -204,6 +362,8 @@ static void print_address_description(void *addr) pr_err("The buggy address belongs to the page:\n"); dump_page(page, "kasan: bad access detected"); } + + print_address_stack_frame(addr); } static bool row_is_guilty(const void *row, const void *guilty) -- 2.21.0.1020.gf2820cf01a-goog