From: Todd Kjos Date: Thu, 29 Jun 2017 19:01:53 +0000 (-0700) Subject: binder: use atomic for transaction_log index X-Git-Tag: v4.14-rc1~146^2~202 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=d99c7333ab1c9d56e6f6e15c0b4398591465efc1;p=linux.git binder: use atomic for transaction_log index The log->next index for the transaction log was not protected when incremented. This led to a case where log->next++ resulted in an index larger than ARRAY_SIZE(log->entry) and eventually a bad access to memory. Fixed by making the log index an atomic64 and converting to an array by using "% ARRAY_SIZE(log->entry)" Also added "complete" field to the log entry which is written last to tell the print code whether the entry is complete Signed-off-by: Todd Kjos Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/android/binder.c b/drivers/android/binder.c index a1912a22c89c..cb78a4e6872d 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -187,6 +187,7 @@ static inline void binder_stats_created(enum binder_stat_types type) struct binder_transaction_log_entry { int debug_id; + int debug_id_done; int call_type; int from_proc; int from_thread; @@ -202,8 +203,8 @@ struct binder_transaction_log_entry { const char *context_name; }; struct binder_transaction_log { - int next; - int full; + atomic_t cur; + bool full; struct binder_transaction_log_entry entry[32]; }; static struct binder_transaction_log binder_transaction_log; @@ -213,14 +214,19 @@ static struct binder_transaction_log_entry *binder_transaction_log_add( struct binder_transaction_log *log) { struct binder_transaction_log_entry *e; + unsigned int cur = atomic_inc_return(&log->cur); - e = &log->entry[log->next]; - memset(e, 0, sizeof(*e)); - log->next++; - if (log->next == ARRAY_SIZE(log->entry)) { - log->next = 0; + if (cur >= ARRAY_SIZE(log->entry)) log->full = 1; - } + e = &log->entry[cur % ARRAY_SIZE(log->entry)]; + WRITE_ONCE(e->debug_id_done, 0); + /* + * write-barrier to synchronize access to e->debug_id_done. + * We make sure the initialized 0 value is seen before + * memset() other fields are zeroed by memset. + */ + smp_wmb(); + memset(e, 0, sizeof(*e)); return e; } @@ -1400,8 +1406,10 @@ static void binder_transaction(struct binder_proc *proc, struct binder_buffer_object *last_fixup_obj = NULL; binder_size_t last_fixup_min_off = 0; struct binder_context *context = proc->context; + int t_debug_id = atomic_inc_return(&binder_last_id); e = binder_transaction_log_add(&binder_transaction_log); + e->debug_id = t_debug_id; e->call_type = reply ? 2 : !!(tr->flags & TF_ONE_WAY); e->from_proc = proc->pid; e->from_thread = thread->pid; @@ -1545,8 +1553,7 @@ static void binder_transaction(struct binder_proc *proc, } binder_stats_created(BINDER_STAT_TRANSACTION_COMPLETE); - t->debug_id = atomic_inc_return(&binder_last_id); - e->debug_id = t->debug_id; + t->debug_id = t_debug_id; if (reply) binder_debug(BINDER_DEBUG_TRANSACTION, @@ -1821,6 +1828,12 @@ static void binder_transaction(struct binder_proc *proc, else wake_up_interruptible(target_wait); } + /* + * write barrier to synchronize with initialization + * of log entry + */ + smp_wmb(); + WRITE_ONCE(e->debug_id_done, t_debug_id); return; err_translate_failed: @@ -1858,6 +1871,13 @@ static void binder_transaction(struct binder_proc *proc, e->return_error_line = return_error_line; fe = binder_transaction_log_add(&binder_transaction_log_failed); *fe = *e; + /* + * write barrier to synchronize with initialization + * of log entry + */ + smp_wmb(); + WRITE_ONCE(e->debug_id_done, t_debug_id); + WRITE_ONCE(fe->debug_id_done, t_debug_id); } BUG_ON(thread->return_error != BR_OK); @@ -3718,27 +3738,47 @@ static int binder_proc_show(struct seq_file *m, void *unused) static void print_binder_transaction_log_entry(struct seq_file *m, struct binder_transaction_log_entry *e) { + int debug_id = READ_ONCE(e->debug_id_done); + /* + * read barrier to guarantee debug_id_done read before + * we print the log values + */ + smp_rmb(); seq_printf(m, - "%d: %s from %d:%d to %d:%d context %s node %d handle %d size %d:%d ret %d/%d l=%d\n", + "%d: %s from %d:%d to %d:%d context %s node %d handle %d size %d:%d ret %d/%d l=%d", e->debug_id, (e->call_type == 2) ? "reply" : ((e->call_type == 1) ? "async" : "call "), e->from_proc, e->from_thread, e->to_proc, e->to_thread, e->context_name, e->to_node, e->target_handle, e->data_size, e->offsets_size, e->return_error, e->return_error_param, e->return_error_line); + /* + * read-barrier to guarantee read of debug_id_done after + * done printing the fields of the entry + */ + smp_rmb(); + seq_printf(m, debug_id && debug_id == READ_ONCE(e->debug_id_done) ? + "\n" : " (incomplete)\n"); } static int binder_transaction_log_show(struct seq_file *m, void *unused) { struct binder_transaction_log *log = m->private; + unsigned int log_cur = atomic_read(&log->cur); + unsigned int count; + unsigned int cur; int i; - if (log->full) { - for (i = log->next; i < ARRAY_SIZE(log->entry); i++) - print_binder_transaction_log_entry(m, &log->entry[i]); + count = log_cur + 1; + cur = count < ARRAY_SIZE(log->entry) && !log->full ? + 0 : count % ARRAY_SIZE(log->entry); + if (count > ARRAY_SIZE(log->entry) || log->full) + count = ARRAY_SIZE(log->entry); + for (i = 0; i < count; i++) { + unsigned int index = cur++ % ARRAY_SIZE(log->entry); + + print_binder_transaction_log_entry(m, &log->entry[index]); } - for (i = 0; i < log->next; i++) - print_binder_transaction_log_entry(m, &log->entry[i]); return 0; } @@ -3793,6 +3833,9 @@ static int __init binder_init(void) struct binder_device *device; struct hlist_node *tmp; + atomic_set(&binder_transaction_log.cur, ~0U); + atomic_set(&binder_transaction_log_failed.cur, ~0U); + binder_debugfs_dir_entry_root = debugfs_create_dir("binder", NULL); if (binder_debugfs_dir_entry_root) binder_debugfs_dir_entry_proc = debugfs_create_dir("proc",