git: 300cfb96fc22 - main - file: Make fget*() and getvnode*() consistent about initializing *fpp

The branch main has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=300cfb96fc2253c3aff8d501d5599fcf811daa34

commit 300cfb96fc2253c3aff8d501d5599fcf811daa34
Author:     Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2022-02-08 17:34:20 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2022-02-08 17:40:41 +0000

    file: Make fget*() and getvnode*() consistent about initializing *fpp
    
    Most fget*() functions initialize the output parameter to NULL.  Make
    the externally visible interface behave consistently, and make
    fget_unlocked_seq() private to kern_descrip.c.
    
    This fixes at least one bug in a consumer, _filemon_wrapper_openat(),
    which assumes that getvnode() sets the output file pointer to NULL upon
    an error.
    
    Reported by:    syzbot+01c0459408f896a5933a@syzkaller.appspotmail.com
    Reviewed by:    kib
    MFC after:      1 week
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D34190
---
 sys/kern/kern_descrip.c | 12 ++++++++++--
 sys/kern/vfs_syscalls.c |  2 ++
 sys/sys/filedesc.h      |  3 ---
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index d5d22ecfc522..c4cf9abde664 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -115,6 +115,8 @@ static void	fdgrowtable(struct filedesc *fdp, int nfd);
 static void	fdgrowtable_exp(struct filedesc *fdp, int nfd);
 static void	fdunused(struct filedesc *fdp, int fd);
 static void	fdused(struct filedesc *fdp, int fd);
+static int	fget_unlocked_seq(struct filedesc *fdp, int fd,
+		    cap_rights_t *needrightsp, struct file **fpp, seqc_t *seqp);
 static int	getmaxfd(struct thread *td);
 static u_long	*filecaps_copy_prep(const struct filecaps *src);
 static void	filecaps_copy_finish(const struct filecaps *src,
@@ -2843,6 +2845,7 @@ fget_cap_locked(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
 
 	FILEDESC_LOCK_ASSERT(fdp);
 
+	*fpp = NULL;
 	fde = fdeget_locked(fdp, fd);
 	if (fde == NULL) {
 		error = EBADF;
@@ -3014,7 +3017,7 @@ fgetvp_lookup_smr(int fd, struct nameidata *ndp, struct vnode **vpp, bool *fsear
 }
 #endif
 
-int
+static int
 fget_unlocked_seq(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
     struct file **fpp, seqc_t *seqp)
 {
@@ -3112,8 +3115,10 @@ fget_unlocked(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
 #endif
 
 	fdt = fdp->fd_files;
-	if (__predict_false((u_int)fd >= fdt->fdt_nfiles))
+	if (__predict_false((u_int)fd >= fdt->fdt_nfiles)) {
+		*fpp = NULL;
 		return (EBADF);
+	}
 #ifdef CAPABILITIES
 	seq = seqc_read_notmodify(fd_seqc(fdt, fd));
 	fde = &fdt->fdt_ofiles[fd];
@@ -3148,6 +3153,7 @@ fget_unlocked(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
 out_fdrop:
 	fdrop(fp, curthread);
 out_fallback:
+	*fpp = NULL;
 	return (fget_unlocked_seq(fdp, fd, needrightsp, fpp, NULL));
 }
 
@@ -3173,6 +3179,7 @@ fget_only_user(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
 
 	MPASS(FILEDESC_IS_ONLY_USER(fdp));
 
+	*fpp = NULL;
 	if (__predict_false(fd >= fdp->fd_nfiles))
 		return (EBADF);
 
@@ -3198,6 +3205,7 @@ fget_only_user(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
 
 	MPASS(FILEDESC_IS_ONLY_USER(fdp));
 
+	*fpp = NULL;
 	if (__predict_false(fd >= fdp->fd_nfiles))
 		return (EBADF);
 
diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index 3e0b96051465..5549cae570f8 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -4336,6 +4336,7 @@ getvnode_path(struct thread *td, int fd, cap_rights_t *rightsp,
 	 */
 	if (__predict_false(fp->f_vnode == NULL || fp->f_ops == &badfileops)) {
 		fdrop(fp, td);
+		*fpp = NULL;
 		return (EINVAL);
 	}
 
@@ -4363,6 +4364,7 @@ getvnode(struct thread *td, int fd, cap_rights_t *rightsp, struct file **fpp)
 	 */
 	if (__predict_false((*fpp)->f_ops == &path_fileops)) {
 		fdrop(*fpp, td);
+		*fpp = NULL;
 		error = EBADF;
 	}
 
diff --git a/sys/sys/filedesc.h b/sys/sys/filedesc.h
index 6f0e74e70d3b..f003c0ff3c4b 100644
--- a/sys/sys/filedesc.h
+++ b/sys/sys/filedesc.h
@@ -269,10 +269,7 @@ int	fget_cap_locked(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
 	    struct file **fpp, struct filecaps *havecapsp);
 int	fget_cap(struct thread *td, int fd, cap_rights_t *needrightsp,
 	    struct file **fpp, struct filecaps *havecapsp);
-
 /* Return a referenced file from an unlocked descriptor. */
-int	fget_unlocked_seq(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
-	    struct file **fpp, seqc_t *seqp);
 int	fget_unlocked(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
 	    struct file **fpp);
 /* Return a file pointer without a ref. FILEDESC_IS_ONLY_USER must be true.  */