Use the helper fget_task to simplify bpf_task_fd_query. As well as simplifying the code this removes one unnecessary increment of struct files_struct. This unnecessary increment of files_struct.count can result in exec unnecessarily unsharing files_struct and breaking posix locks, and it can result in fget_light having to fallback to fget reducing performance. This simplification comes from the observation that none of the callers of get_files_struct actually need to call get_files_struct that was made when discussing[1] exec and posix file locks. [1] https://lkml.kernel.org/r/20180915160423.GA31461@xxxxxxxxxx Suggested-by: Oleg Nesterov <oleg@xxxxxxxxxx> v1: https://lkml.kernel.org/r/20200817220425.9389-5-ebiederm@xxxxxxxxxxxx Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> --- kernel/bpf/syscall.c | 20 +++----------------- 1 file changed, 3 insertions(+), 17 deletions(-) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 8f50c9c19f1b..6d49c2e1634c 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -3878,7 +3878,6 @@ static int bpf_task_fd_query(const union bpf_attr *attr, pid_t pid = attr->task_fd_query.pid; u32 fd = attr->task_fd_query.fd; const struct perf_event *event; - struct files_struct *files; struct task_struct *task; struct file *file; int err; @@ -3896,23 +3895,11 @@ static int bpf_task_fd_query(const union bpf_attr *attr, if (!task) return -ENOENT; - files = get_files_struct(task); - put_task_struct(task); - if (!files) - return -ENOENT; - err = 0; - spin_lock(&files->file_lock); - file = fcheck_files(files, fd); + file = fget_task(task, fd); + put_task_struct(task); if (!file) - err = -EBADF; - else - get_file(file); - spin_unlock(&files->file_lock); - put_files_struct(files); - - if (err) - goto out; + return -EBADF; if (file->f_op == &bpf_link_fops) { struct bpf_link *link = file->private_data; @@ -3952,7 +3939,6 @@ static int bpf_task_fd_query(const union bpf_attr *attr, err = -ENOTSUPP; put_file: fput(file); -out: return err; } -- 2.25.0
