From 448f97fba9013ffa13f5dd82febd18836b189499 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 12 Aug 2025 12:39:13 +0200 Subject: [PATCH] perf: Convert mmap() refcounts to refcount_t The recently fixed reference count leaks could have been detected by using refcount_t and refcount_t would have mitigated the potential overflow at least. Now that the code is properly structured, convert the mmap() related mmap_count variants over to refcount_t. No functional change intended. Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Lorenzo Stoakes Link: https://lore.kernel.org/r/20250812104020.071507932@infradead.org --- include/linux/perf_event.h | 2 +- kernel/events/core.c | 40 ++++++++++++++++++------------------- kernel/events/internal.h | 4 ++-- kernel/events/ring_buffer.c | 2 +- 4 files changed, 24 insertions(+), 24 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index ec9d960256839..bfbf9ea53f259 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -859,7 +859,7 @@ struct perf_event { /* mmap bits */ struct mutex mmap_mutex; - atomic_t mmap_count; + refcount_t mmap_count; struct perf_buffer *rb; struct list_head rb_entry; diff --git a/kernel/events/core.c b/kernel/events/core.c index f6211ab185036..ea357044d7806 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3968,7 +3968,7 @@ static noinline int visit_groups_merge(struct perf_event_context *ctx, */ static inline bool event_update_userpage(struct perf_event *event) { - if (likely(!atomic_read(&event->mmap_count))) + if (likely(!refcount_read(&event->mmap_count))) return false; perf_event_update_time(event); @@ -6704,11 +6704,11 @@ static void perf_mmap_open(struct vm_area_struct *vma) struct perf_event *event = vma->vm_file->private_data; mapped_f mapped = get_mapped(event, event_mapped); - atomic_inc(&event->mmap_count); - atomic_inc(&event->rb->mmap_count); + refcount_inc(&event->mmap_count); + refcount_inc(&event->rb->mmap_count); if (vma->vm_pgoff) - atomic_inc(&event->rb->aux_mmap_count); + refcount_inc(&event->rb->aux_mmap_count); if (mapped) mapped(event, vma->vm_mm); @@ -6743,7 +6743,7 @@ static void perf_mmap_close(struct vm_area_struct *vma) * to avoid complications. */ if (rb_has_aux(rb) && vma->vm_pgoff == rb->aux_pgoff && - atomic_dec_and_mutex_lock(&rb->aux_mmap_count, &rb->aux_mutex)) { + refcount_dec_and_mutex_lock(&rb->aux_mmap_count, &rb->aux_mutex)) { /* * Stop all AUX events that are writing to this buffer, * so that we can free its AUX pages and corresponding PMU @@ -6763,10 +6763,10 @@ static void perf_mmap_close(struct vm_area_struct *vma) mutex_unlock(&rb->aux_mutex); } - if (atomic_dec_and_test(&rb->mmap_count)) + if (refcount_dec_and_test(&rb->mmap_count)) detach_rest = true; - if (!atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) + if (!refcount_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) goto out_put; ring_buffer_attach(event, NULL); @@ -6992,19 +6992,19 @@ static int perf_mmap_rb(struct vm_area_struct *vma, struct perf_event *event, if (data_page_nr(event->rb) != nr_pages) return -EINVAL; - if (atomic_inc_not_zero(&event->rb->mmap_count)) { + if (refcount_inc_not_zero(&event->rb->mmap_count)) { /* * Success -- managed to mmap() the same buffer * multiple times. */ perf_mmap_account(vma, user_extra, extra); - atomic_inc(&event->mmap_count); + refcount_inc(&event->mmap_count); return 0; } /* * Raced against perf_mmap_close()'s - * atomic_dec_and_mutex_lock() remove the + * refcount_dec_and_mutex_lock() remove the * event and continue as if !event->rb */ ring_buffer_attach(event, NULL); @@ -7023,7 +7023,7 @@ static int perf_mmap_rb(struct vm_area_struct *vma, struct perf_event *event, if (!rb) return -ENOMEM; - atomic_set(&rb->mmap_count, 1); + refcount_set(&rb->mmap_count, 1); rb->mmap_user = get_current_user(); rb->mmap_locked = extra; @@ -7034,7 +7034,7 @@ static int perf_mmap_rb(struct vm_area_struct *vma, struct perf_event *event, perf_event_update_userpage(event); perf_mmap_account(vma, user_extra, extra); - atomic_set(&event->mmap_count, 1); + refcount_set(&event->mmap_count, 1); return 0; } @@ -7081,15 +7081,15 @@ static int perf_mmap_aux(struct vm_area_struct *vma, struct perf_event *event, if (!is_power_of_2(nr_pages)) return -EINVAL; - if (!atomic_inc_not_zero(&rb->mmap_count)) + if (!refcount_inc_not_zero(&rb->mmap_count)) return -EINVAL; if (rb_has_aux(rb)) { - atomic_inc(&rb->aux_mmap_count); + refcount_inc(&rb->aux_mmap_count); } else { if (!perf_mmap_calc_limits(vma, &user_extra, &extra)) { - atomic_dec(&rb->mmap_count); + refcount_dec(&rb->mmap_count); return -EPERM; } @@ -7101,16 +7101,16 @@ static int perf_mmap_aux(struct vm_area_struct *vma, struct perf_event *event, ret = rb_alloc_aux(rb, event, vma->vm_pgoff, nr_pages, event->attr.aux_watermark, rb_flags); if (ret) { - atomic_dec(&rb->mmap_count); + refcount_dec(&rb->mmap_count); return ret; } - atomic_set(&rb->aux_mmap_count, 1); + refcount_set(&rb->aux_mmap_count, 1); rb->aux_mmap_locked = extra; } perf_mmap_account(vma, user_extra, extra); - atomic_inc(&event->mmap_count); + refcount_inc(&event->mmap_count); return 0; } @@ -13254,7 +13254,7 @@ perf_event_set_output(struct perf_event *event, struct perf_event *output_event) mutex_lock_double(&event->mmap_mutex, &output_event->mmap_mutex); set: /* Can't redirect output if we've got an active mmap() */ - if (atomic_read(&event->mmap_count)) + if (refcount_read(&event->mmap_count)) goto unlock; if (output_event) { @@ -13267,7 +13267,7 @@ set: goto unlock; /* did we race against perf_mmap_close() */ - if (!atomic_read(&rb->mmap_count)) { + if (!refcount_read(&rb->mmap_count)) { ring_buffer_put(rb); goto unlock; } diff --git a/kernel/events/internal.h b/kernel/events/internal.h index 249288d82b8dc..d9cc570830918 100644 --- a/kernel/events/internal.h +++ b/kernel/events/internal.h @@ -35,7 +35,7 @@ struct perf_buffer { spinlock_t event_lock; struct list_head event_list; - atomic_t mmap_count; + refcount_t mmap_count; unsigned long mmap_locked; struct user_struct *mmap_user; @@ -47,7 +47,7 @@ struct perf_buffer { unsigned long aux_pgoff; int aux_nr_pages; int aux_overwrite; - atomic_t aux_mmap_count; + refcount_t aux_mmap_count; unsigned long aux_mmap_locked; void (*free_aux)(void *); refcount_t aux_refcount; diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index aa9a759e824fe..20a9050237362 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -400,7 +400,7 @@ void *perf_aux_output_begin(struct perf_output_handle *handle, * the same order, see perf_mmap_close. Otherwise we end up freeing * aux pages in this path, which is a bug, because in_atomic(). */ - if (!atomic_read(&rb->aux_mmap_count)) + if (!refcount_read(&rb->aux_mmap_count)) goto err; if (!refcount_inc_not_zero(&rb->aux_refcount)) -- 2.47.3