diff options
| -rw-r--r-- | kernel/bpf/task_iter.c | 39 | ||||
| -rw-r--r-- | tools/testing/selftests/bpf/prog_tests/bpf_iter.c | 73 |
2 files changed, 100 insertions, 12 deletions
diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index c2a2182ce570..c4ab9d6cdbe9 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -438,6 +438,7 @@ struct bpf_iter_seq_task_vma_info { */ struct bpf_iter_seq_task_common common; struct task_struct *task; + struct mm_struct *mm; struct vm_area_struct *vma; u32 tid; unsigned long prev_vm_start; @@ -456,16 +457,19 @@ task_vma_seq_get_next(struct bpf_iter_seq_task_vma_info *info) enum bpf_task_vma_iter_find_op op; struct vm_area_struct *curr_vma; struct task_struct *curr_task; + struct mm_struct *curr_mm; u32 saved_tid = info->tid; /* If this function returns a non-NULL vma, it holds a reference to - * the task_struct, and holds read lock on vma->mm->mmap_lock. + * the task_struct, holds a refcount on mm->mm_users, and holds + * read lock on vma->mm->mmap_lock. * If this function returns NULL, it does not hold any reference or * lock. */ if (info->task) { curr_task = info->task; curr_vma = info->vma; + curr_mm = info->mm; /* In case of lock contention, drop mmap_lock to unblock * the writer. * @@ -504,13 +508,15 @@ task_vma_seq_get_next(struct bpf_iter_seq_task_vma_info *info) * 4.2) VMA2 and VMA2' covers different ranges, process * VMA2'. */ - if (mmap_lock_is_contended(curr_task->mm)) { + if (mmap_lock_is_contended(curr_mm)) { info->prev_vm_start = curr_vma->vm_start; info->prev_vm_end = curr_vma->vm_end; op = task_vma_iter_find_vma; - mmap_read_unlock(curr_task->mm); - if (mmap_read_lock_killable(curr_task->mm)) + mmap_read_unlock(curr_mm); + if (mmap_read_lock_killable(curr_mm)) { + mmput(curr_mm); goto finish; + } } else { op = task_vma_iter_next_vma; } @@ -535,42 +541,47 @@ again: op = task_vma_iter_find_vma; } - if (!curr_task->mm) + curr_mm = get_task_mm(curr_task); + if (!curr_mm) goto next_task; - if (mmap_read_lock_killable(curr_task->mm)) + if (mmap_read_lock_killable(curr_mm)) { + mmput(curr_mm); goto finish; + } } switch (op) { case task_vma_iter_first_vma: - curr_vma = find_vma(curr_task->mm, 0); + curr_vma = find_vma(curr_mm, 0); break; case task_vma_iter_next_vma: - curr_vma = find_vma(curr_task->mm, curr_vma->vm_end); + curr_vma = find_vma(curr_mm, curr_vma->vm_end); break; case task_vma_iter_find_vma: /* We dropped mmap_lock so it is necessary to use find_vma * to find the next vma. This is similar to the mechanism * in show_smaps_rollup(). */ - curr_vma = find_vma(curr_task->mm, info->prev_vm_end - 1); + curr_vma = find_vma(curr_mm, info->prev_vm_end - 1); /* case 1) and 4.2) above just use curr_vma */ /* check for case 2) or case 4.1) above */ if (curr_vma && curr_vma->vm_start == info->prev_vm_start && curr_vma->vm_end == info->prev_vm_end) - curr_vma = find_vma(curr_task->mm, curr_vma->vm_end); + curr_vma = find_vma(curr_mm, curr_vma->vm_end); break; } if (!curr_vma) { /* case 3) above, or case 2) 4.1) with vma->next == NULL */ - mmap_read_unlock(curr_task->mm); + mmap_read_unlock(curr_mm); + mmput(curr_mm); goto next_task; } info->task = curr_task; info->vma = curr_vma; + info->mm = curr_mm; return curr_vma; next_task: @@ -579,6 +590,7 @@ next_task: put_task_struct(curr_task); info->task = NULL; + info->mm = NULL; info->tid++; goto again; @@ -587,6 +599,7 @@ finish: put_task_struct(curr_task); info->task = NULL; info->vma = NULL; + info->mm = NULL; return NULL; } @@ -658,7 +671,9 @@ static void task_vma_seq_stop(struct seq_file *seq, void *v) */ info->prev_vm_start = ~0UL; info->prev_vm_end = info->vma->vm_end; - mmap_read_unlock(info->task->mm); + mmap_read_unlock(info->mm); + mmput(info->mm); + info->mm = NULL; put_task_struct(info->task); info->task = NULL; } diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c index 6f8ed61fc4b4..3af6450763e9 100644 --- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c +++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c @@ -1465,6 +1465,77 @@ out: bpf_iter_task_vma__destroy(skel); } +static void test_task_vma_dead_task(void) +{ + struct bpf_iter_task_vma *skel; + int wstatus, child_pid = -1; + time_t start_tm, cur_tm; + int err, iter_fd = -1; + int wait_sec = 3; + + skel = bpf_iter_task_vma__open(); + if (!ASSERT_OK_PTR(skel, "bpf_iter_task_vma__open")) + return; + + skel->bss->pid = getpid(); + + err = bpf_iter_task_vma__load(skel); + if (!ASSERT_OK(err, "bpf_iter_task_vma__load")) + goto out; + + skel->links.proc_maps = bpf_program__attach_iter( + skel->progs.proc_maps, NULL); + + if (!ASSERT_OK_PTR(skel->links.proc_maps, "bpf_program__attach_iter")) { + skel->links.proc_maps = NULL; + goto out; + } + + start_tm = time(NULL); + cur_tm = start_tm; + + child_pid = fork(); + if (child_pid == 0) { + /* Fork short-lived processes in the background. */ + while (cur_tm < start_tm + wait_sec) { + system("echo > /dev/null"); + cur_tm = time(NULL); + } + exit(0); + } + + if (!ASSERT_GE(child_pid, 0, "fork_child")) + goto out; + + while (cur_tm < start_tm + wait_sec) { + iter_fd = bpf_iter_create(bpf_link__fd(skel->links.proc_maps)); + if (!ASSERT_GE(iter_fd, 0, "create_iter")) + goto out; + + /* Drain all data from iter_fd. */ + while (cur_tm < start_tm + wait_sec) { + err = read_fd_into_buffer(iter_fd, task_vma_output, CMP_BUFFER_SIZE); + if (!ASSERT_GE(err, 0, "read_iter_fd")) + goto out; + + cur_tm = time(NULL); + + if (err == 0) + break; + } + + close(iter_fd); + iter_fd = -1; + } + + check_bpf_link_info(skel->progs.proc_maps); + +out: + waitpid(child_pid, &wstatus, 0); + close(iter_fd); + bpf_iter_task_vma__destroy(skel); +} + void test_bpf_sockmap_map_iter_fd(void) { struct bpf_iter_sockmap *skel; @@ -1586,6 +1657,8 @@ void test_bpf_iter(void) test_task_file(); if (test__start_subtest("task_vma")) test_task_vma(); + if (test__start_subtest("task_vma_dead_task")) + test_task_vma_dead_task(); if (test__start_subtest("task_btf")) test_task_btf(); if (test__start_subtest("tcp4")) |