Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933214Ab0GAVdI (ORCPT ); Thu, 1 Jul 2010 17:33:08 -0400 Received: from kroah.org ([198.145.64.141]:33171 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759010Ab0GAVPI (ORCPT ); Thu, 1 Jul 2010 17:15:08 -0400 X-Mailbox-Line: From gregkh@clark.site Thu Jul 1 10:43:00 2010 Message-Id: <20100701174300.821159901@clark.site> User-Agent: quilt/0.48-10.1 Date: Thu, 01 Jul 2010 10:44:19 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Peter Zijlstra , Ingo Molnar Subject: [169/200] perf_events: Fix races and clean up perf_event and perf_mmap_data interaction In-Reply-To: <20100701175201.GA2149@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 12376 Lines: 459 2.6.34-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra commit ac9721f3f54b27a16c7e1afb2481e7ee95a70318 upstream. In order to move toward separate buffer objects, rework the whole perf_mmap_data construct to be a more self-sufficient entity, one with its own lifetime rules. This greatly sanitizes the whole output redirection code, which was riddled with bugs and races. Signed-off-by: Peter Zijlstra LKML-Reference: Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- include/linux/perf_event.h | 5 - kernel/perf_event.c | 217 ++++++++++++++++++++++++++------------------- 2 files changed, 129 insertions(+), 93 deletions(-) --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -531,6 +531,7 @@ enum perf_event_active_state { struct file; struct perf_mmap_data { + atomic_t refcount; struct rcu_head rcu_head; #ifdef CONFIG_PERF_USE_VMALLOC struct work_struct work; @@ -538,7 +539,6 @@ struct perf_mmap_data { int data_order; int nr_pages; /* nr of data pages */ int writable; /* are we writable */ - int nr_locked; /* nr pages mlocked */ atomic_t poll; /* POLL_ for wakeups */ atomic_t events; /* event_id limit */ @@ -582,7 +582,6 @@ struct perf_event { int nr_siblings; int group_flags; struct perf_event *group_leader; - struct perf_event *output; const struct pmu *pmu; enum perf_event_active_state state; @@ -643,6 +642,8 @@ struct perf_event { /* mmap bits */ struct mutex mmap_mutex; atomic_t mmap_count; + int mmap_locked; + struct user_struct *mmap_user; struct perf_mmap_data *data; /* poll related */ --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -1832,6 +1832,7 @@ static void free_event_rcu(struct rcu_he } static void perf_pending_sync(struct perf_event *event); +static void perf_mmap_data_put(struct perf_mmap_data *data); static void free_event(struct perf_event *event) { @@ -1847,9 +1848,9 @@ static void free_event(struct perf_event atomic_dec(&nr_task_events); } - if (event->output) { - fput(event->output->filp); - event->output = NULL; + if (event->data) { + perf_mmap_data_put(event->data); + event->data = NULL; } if (event->destroy) @@ -2154,7 +2155,27 @@ unlock: return ret; } -static int perf_event_set_output(struct perf_event *event, int output_fd); +static const struct file_operations perf_fops; + +static struct perf_event *perf_fget_light(int fd, int *fput_needed) +{ + struct file *file; + + file = fget_light(fd, fput_needed); + if (!file) + return ERR_PTR(-EBADF); + + if (file->f_op != &perf_fops) { + fput_light(file, *fput_needed); + *fput_needed = 0; + return ERR_PTR(-EBADF); + } + + return file->private_data; +} + +static int perf_event_set_output(struct perf_event *event, + struct perf_event *output_event); static int perf_event_set_filter(struct perf_event *event, void __user *arg); static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg) @@ -2181,7 +2202,23 @@ static long perf_ioctl(struct file *file return perf_event_period(event, (u64 __user *)arg); case PERF_EVENT_IOC_SET_OUTPUT: - return perf_event_set_output(event, arg); + { + struct perf_event *output_event = NULL; + int fput_needed = 0; + int ret; + + if (arg != -1) { + output_event = perf_fget_light(arg, &fput_needed); + if (IS_ERR(output_event)) + return PTR_ERR(output_event); + } + + ret = perf_event_set_output(event, output_event); + if (output_event) + fput_light(output_event->filp, fput_needed); + + return ret; + } case PERF_EVENT_IOC_SET_FILTER: return perf_event_set_filter(event, (void __user *)arg); @@ -2306,8 +2343,6 @@ perf_mmap_data_alloc(struct perf_event * unsigned long size; int i; - WARN_ON(atomic_read(&event->mmap_count)); - size = sizeof(struct perf_mmap_data); size += nr_pages * sizeof(void *); @@ -2414,8 +2449,6 @@ perf_mmap_data_alloc(struct perf_event * unsigned long size; void *all_buf; - WARN_ON(atomic_read(&event->mmap_count)); - size = sizeof(struct perf_mmap_data); size += sizeof(void *); @@ -2495,7 +2528,7 @@ perf_mmap_data_init(struct perf_event *e if (!data->watermark) data->watermark = max_size / 2; - + atomic_set(&data->refcount, 1); rcu_assign_pointer(event->data, data); } @@ -2507,13 +2540,26 @@ static void perf_mmap_data_free_rcu(stru perf_mmap_data_free(data); } -static void perf_mmap_data_release(struct perf_event *event) +static struct perf_mmap_data *perf_mmap_data_get(struct perf_event *event) { - struct perf_mmap_data *data = event->data; + struct perf_mmap_data *data; + + rcu_read_lock(); + data = rcu_dereference(event->data); + if (data) { + if (!atomic_inc_not_zero(&data->refcount)) + data = NULL; + } + rcu_read_unlock(); - WARN_ON(atomic_read(&event->mmap_count)); + return data; +} + +static void perf_mmap_data_put(struct perf_mmap_data *data) +{ + if (!atomic_dec_and_test(&data->refcount)) + return; - rcu_assign_pointer(event->data, NULL); call_rcu(&data->rcu_head, perf_mmap_data_free_rcu); } @@ -2528,15 +2574,18 @@ static void perf_mmap_close(struct vm_ar { struct perf_event *event = vma->vm_file->private_data; - WARN_ON_ONCE(event->ctx->parent_ctx); if (atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) { unsigned long size = perf_data_size(event->data); - struct user_struct *user = current_user(); + struct user_struct *user = event->mmap_user; + struct perf_mmap_data *data = event->data; atomic_long_sub((size >> PAGE_SHIFT) + 1, &user->locked_vm); - vma->vm_mm->locked_vm -= event->data->nr_locked; - perf_mmap_data_release(event); + vma->vm_mm->locked_vm -= event->mmap_locked; + rcu_assign_pointer(event->data, NULL); mutex_unlock(&event->mmap_mutex); + + perf_mmap_data_put(data); + free_uid(user); } } @@ -2580,13 +2629,10 @@ static int perf_mmap(struct file *file, WARN_ON_ONCE(event->ctx->parent_ctx); mutex_lock(&event->mmap_mutex); - if (event->output) { - ret = -EINVAL; - goto unlock; - } - - if (atomic_inc_not_zero(&event->mmap_count)) { - if (nr_pages != event->data->nr_pages) + if (event->data) { + if (event->data->nr_pages == nr_pages) + atomic_inc(&event->data->refcount); + else ret = -EINVAL; goto unlock; } @@ -2618,21 +2664,23 @@ static int perf_mmap(struct file *file, WARN_ON(event->data); data = perf_mmap_data_alloc(event, nr_pages); - ret = -ENOMEM; - if (!data) + if (!data) { + ret = -ENOMEM; goto unlock; + } - ret = 0; perf_mmap_data_init(event, data); - - atomic_set(&event->mmap_count, 1); - atomic_long_add(user_extra, &user->locked_vm); - vma->vm_mm->locked_vm += extra; - event->data->nr_locked = extra; if (vma->vm_flags & VM_WRITE) event->data->writable = 1; + atomic_long_add(user_extra, &user->locked_vm); + event->mmap_locked = extra; + event->mmap_user = get_current_user(); + vma->vm_mm->locked_vm += event->mmap_locked; + unlock: + if (!ret) + atomic_inc(&event->mmap_count); mutex_unlock(&event->mmap_mutex); vma->vm_flags |= VM_RESERVED; @@ -2962,7 +3010,6 @@ int perf_output_begin(struct perf_output struct perf_event *event, unsigned int size, int nmi, int sample) { - struct perf_event *output_event; struct perf_mmap_data *data; unsigned long tail, offset, head; int have_lost; @@ -2979,10 +3026,6 @@ int perf_output_begin(struct perf_output if (event->parent) event = event->parent; - output_event = rcu_dereference(event->output); - if (output_event) - event = output_event; - data = rcu_dereference(event->data); if (!data) goto out; @@ -4746,54 +4789,41 @@ err_size: goto out; } -static int perf_event_set_output(struct perf_event *event, int output_fd) +static int +perf_event_set_output(struct perf_event *event, struct perf_event *output_event) { - struct perf_event *output_event = NULL; - struct file *output_file = NULL; - struct perf_event *old_output; - int fput_needed = 0; + struct perf_mmap_data *data = NULL, *old_data = NULL; int ret = -EINVAL; - if (!output_fd) + if (!output_event) goto set; - output_file = fget_light(output_fd, &fput_needed); - if (!output_file) - return -EBADF; - - if (output_file->f_op != &perf_fops) - goto out; - - output_event = output_file->private_data; - - /* Don't chain output fds */ - if (output_event->output) - goto out; - - /* Don't set an output fd when we already have an output channel */ - if (event->data) + /* don't allow circular references */ + if (event == output_event) goto out; - atomic_long_inc(&output_file->f_count); - set: mutex_lock(&event->mmap_mutex); - old_output = event->output; - rcu_assign_pointer(event->output, output_event); - mutex_unlock(&event->mmap_mutex); + /* Can't redirect output if we've got an active mmap() */ + if (atomic_read(&event->mmap_count)) + goto unlock; - if (old_output) { - /* - * we need to make sure no existing perf_output_*() - * is still referencing this event. - */ - synchronize_rcu(); - fput(old_output->filp); + if (output_event) { + /* get the buffer we want to redirect to */ + data = perf_mmap_data_get(output_event); + if (!data) + goto unlock; } + old_data = event->data; + rcu_assign_pointer(event->data, data); ret = 0; +unlock: + mutex_unlock(&event->mmap_mutex); + + if (old_data) + perf_mmap_data_put(old_data); out: - fput_light(output_file, fput_needed); return ret; } @@ -4809,7 +4839,7 @@ SYSCALL_DEFINE5(perf_event_open, struct perf_event_attr __user *, attr_uptr, pid_t, pid, int, cpu, int, group_fd, unsigned long, flags) { - struct perf_event *event, *group_leader; + struct perf_event *event, *group_leader = NULL, *output_event = NULL; struct perf_event_attr attr; struct perf_event_context *ctx; struct file *event_file = NULL; @@ -4840,6 +4870,19 @@ SYSCALL_DEFINE5(perf_event_open, if (event_fd < 0) return event_fd; + if (group_fd != -1) { + group_leader = perf_fget_light(group_fd, &fput_needed); + if (IS_ERR(group_leader)) { + err = PTR_ERR(group_leader); + goto err_put_context; + } + group_file = group_leader->filp; + if (flags & PERF_FLAG_FD_OUTPUT) + output_event = group_leader; + if (flags & PERF_FLAG_FD_NO_GROUP) + group_leader = NULL; + } + /* * Get the target context (task or percpu): */ @@ -4852,16 +4895,9 @@ SYSCALL_DEFINE5(perf_event_open, /* * Look up the group leader (we will attach this event to it): */ - group_leader = NULL; - if (group_fd != -1 && !(flags & PERF_FLAG_FD_NO_GROUP)) { + if (group_leader) { err = -EINVAL; - group_file = fget_light(group_fd, &fput_needed); - if (!group_file) - goto err_put_context; - if (group_file->f_op != &perf_fops) - goto err_put_context; - group_leader = group_file->private_data; /* * Do not allow a recursive hierarchy (this new sibling * becoming part of another group-sibling): @@ -4883,9 +4919,16 @@ SYSCALL_DEFINE5(perf_event_open, event = perf_event_alloc(&attr, cpu, ctx, group_leader, NULL, NULL, GFP_KERNEL); - err = PTR_ERR(event); - if (IS_ERR(event)) + if (IS_ERR(event)) { + err = PTR_ERR(event); goto err_put_context; + } + + if (output_event) { + err = perf_event_set_output(event, output_event); + if (err) + goto err_free_put_context; + } event_file = anon_inode_getfile("[perf_event]", &perf_fops, event, O_RDWR); if (IS_ERR(event_file)) { @@ -4893,12 +4936,6 @@ SYSCALL_DEFINE5(perf_event_open, goto err_free_put_context; } - if (flags & PERF_FLAG_FD_OUTPUT) { - err = perf_event_set_output(event, group_fd); - if (err) - goto err_fput_free_put_context; - } - event->filp = event_file; WARN_ON_ONCE(ctx->parent_ctx); mutex_lock(&ctx->mutex); @@ -4916,8 +4953,6 @@ SYSCALL_DEFINE5(perf_event_open, fd_install(event_fd, event_file); return event_fd; -err_fput_free_put_context: - fput(event_file); err_free_put_context: free_event(event); err_put_context: -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/