/*      $NetBSD: subr_exec_fd.c,v 1.14 2026/01/04 03:17:30 riastradh Exp $      */

/*-
 * Copyright (c) 2008 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: subr_exec_fd.c,v 1.14 2026/01/04 03:17:30 riastradh Exp $");

#include <sys/param.h>

#include <sys/atomic.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/ktrace.h>
#include <sys/mutex.h>
#include <sys/namei.h>
#include <sys/sdt.h>
#include <sys/syslog.h>
#include <sys/vnode.h>

void
fd_ktrexecfd(void)
{
        proc_t *p;
        filedesc_t *fdp;
        fdfile_t *ff;
        lwp_t *l;
        fdtab_t *dt;
        file_t *fp;
        int fd;

        l = curlwp;
        p = l->l_proc;
        fdp = p->p_fd;
        dt = atomic_load_consume(&fdp->fd_dt);

        for (fd = 0; fd <= fdp->fd_lastfile; fd++) {
                if ((ff = dt->dt_ff[fd]) == NULL) {
                        KASSERT(fd >= NDFDFILE);
                        continue;
                }
                KASSERT(fd >= NDFDFILE ||
                    ff == (fdfile_t *)fdp->fd_dfdfile[fd]);
                if ((fp = atomic_load_consume(&ff->ff_file)) == NULL)
                        continue;
                ktr_execfd(fd, fp->f_type);
        }
}

/*
 * It is unsafe for set[ug]id processes to be started with file
 * descriptors 0..2 closed, as these descriptors are given implicit
 * significance in the Standard C library.  fd_checkstd() will create a
 * descriptor referencing /dev/null for each of stdin, stdout, and
 * stderr that is not already open.
 */
#define CHECK_UPTO 3
int
fd_checkstd(void)
{
        struct proc *p;
        struct pathbuf *pb;
        struct vnode *vp;
        filedesc_t *fdp;
        file_t *fp;
        fdtab_t *dt;
        struct proc *pp;
        int fd, i, error, flags = FREAD|FWRITE;
        char closed[CHECK_UPTO * 3 + 1], which[3 + 1];

        p = curproc;
        closed[0] = '\0';
        if ((fdp = p->p_fd) == NULL)
                return 0;
        dt = atomic_load_consume(&fdp->fd_dt);
        for (i = 0; i < CHECK_UPTO; i++) {
                KASSERT(i >= NDFDFILE ||
                    dt->dt_ff[i] == (fdfile_t *)fdp->fd_dfdfile[i]);
                if (dt->dt_ff[i]->ff_file != NULL)
                        continue;
                snprintf(which, sizeof(which), ",%d", i);
                strlcat(closed, which, sizeof(closed));
                if ((error = fd_allocfile(&fp, &fd)) != 0)
                        return error;
                KASSERT(fd < CHECK_UPTO);
                pb = pathbuf_create("/dev/null");
                if (pb == NULL) {
                        return SET_ERROR(ENOMEM);
                }
                error = vn_open(NULL, pb, 0, flags, 0, &vp, NULL, NULL);
                if (error != 0) {
                        pathbuf_destroy(pb);
                        fd_abort(p, fp, fd);
                        return error;
                }
                fp->f_type = DTYPE_VNODE;
                fp->f_vnode = vp;
                fp->f_flag = flags;
                fp->f_ops = &vnops;
                VOP_UNLOCK(vp);
                fd_affix(p, fp, fd);
                pathbuf_destroy(pb);
        }
        if (closed[0] != '\0') {
                mutex_enter(&proc_lock);
                pp = p->p_pptr;
                mutex_enter(pp->p_lock);
                log(LOG_WARNING, "set{u,g}id pid %d (%s) "
                    "was invoked by uid %d ppid %d (%s) "
                    "with fd %s closed\n",
                    p->p_pid, p->p_comm, kauth_cred_geteuid(pp->p_cred),
                    pp->p_pid, pp->p_comm, &closed[1]);
                mutex_exit(pp->p_lock);
                mutex_exit(&proc_lock);
        }
        return 0;
}
#undef CHECK_UPTO