From: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Lift fdget() and fdput() out of perf_fget_light(), turning it into is_perf_file(struct fd f). The life gets easier in both callers if we do fdget() unconditionally, including the case when we are given -1 instead of a descriptor - that avoids a reassignment in perf_event_open(2) and it avoids a nasty temptation in _perf_ioctl() where we must *not* lift output_event out of scope for output. Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx> --- kernel/events/core.c | 49 +++++++++++++++----------------------------- 1 file changed, 16 insertions(+), 33 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index fd2ac9c7fd77..dae815c30514 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5895,18 +5895,9 @@ EXPORT_SYMBOL_GPL(perf_event_period); static const struct file_operations perf_fops; -static inline int perf_fget_light(int fd, struct fd *p) +static inline bool is_perf_file(struct fd f) { - struct fd f = fdget(fd); - if (!fd_file(f)) - return -EBADF; - - if (fd_file(f)->f_op != &perf_fops) { - fdput(f); - return -EBADF; - } - *p = f; - return 0; + return !fd_empty(f) && fd_file(f)->f_op == &perf_fops; } static int perf_event_set_output(struct perf_event *event, @@ -5954,20 +5945,14 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon case PERF_EVENT_IOC_SET_OUTPUT: { - int ret; + CLASS(fd, output)(arg); // arg == -1 => empty + struct perf_event *output_event = NULL; if (arg != -1) { - struct perf_event *output_event; - struct fd output; - ret = perf_fget_light(arg, &output); - if (ret) - return ret; + if (!is_perf_file(output)) + return -EBADF; output_event = fd_file(output)->private_data; - ret = perf_event_set_output(event, output_event); - fdput(output); - } else { - ret = perf_event_set_output(event, NULL); } - return ret; + return perf_event_set_output(event, output_event); } case PERF_EVENT_IOC_SET_FILTER: @@ -12474,7 +12459,6 @@ SYSCALL_DEFINE5(perf_event_open, struct perf_event_attr attr; struct perf_event_context *ctx; struct file *event_file = NULL; - struct fd group = EMPTY_FD; struct task_struct *task = NULL; struct pmu *pmu; int event_fd; @@ -12545,10 +12529,12 @@ SYSCALL_DEFINE5(perf_event_open, if (event_fd < 0) return event_fd; + CLASS(fd, group)(group_fd); // group_fd == -1 => empty if (group_fd != -1) { - err = perf_fget_light(group_fd, &group); - if (err) + if (!is_perf_file(group)) { + err = -EBADF; goto err_fd; + } group_leader = fd_file(group)->private_data; if (flags & PERF_FLAG_FD_OUTPUT) output_event = group_leader; @@ -12560,7 +12546,7 @@ SYSCALL_DEFINE5(perf_event_open, task = find_lively_task_by_vpid(pid); if (IS_ERR(task)) { err = PTR_ERR(task); - goto err_group_fd; + goto err_fd; } } @@ -12827,12 +12813,11 @@ SYSCALL_DEFINE5(perf_event_open, mutex_unlock(¤t->perf_event_mutex); /* - * Drop the reference on the group_event after placing the - * new event on the sibling_list. This ensures destruction - * of the group leader will find the pointer to itself in - * perf_group_detach(). + * File reference in group guarantees that group_leader has been + * kept alive until we place the new event on the sibling_list. + * This ensures destruction of the group leader will find + * the pointer to itself in perf_group_detach(). */ - fdput(group); fd_install(event_fd, event_file); return event_fd; @@ -12851,8 +12836,6 @@ SYSCALL_DEFINE5(perf_event_open, err_task: if (task) put_task_struct(task); -err_group_fd: - fdput(group); err_fd: put_unused_fd(event_fd); return err; -- 2.39.2