The branch stable/13 has been updated by rmacklem:
URL:
https://cgit.FreeBSD.org/src/commit/?id=527e6b02d65db8d6294b1e66f7bd063899a4de02
commit 527e6b02d65db8d6294b1e66f7bd063899a4de02
Author: Rick Macklem <rmack...@freebsd.org>
AuthorDate: 2023-03-02 21:09:01 +0000
Commit: Rick Macklem <rmack...@freebsd.org>
CommitDate: 2023-05-19 20:23:27 +0000
vfs_mount.c: Allow mountd(8) to do exports in a vnet prison
To run mountd in a vnet prison, three checks in vfs_domount()
and vfs_domount_update() related to doing exports needed
to be changed, so that a file system visible within the
prison but mounted outside the prison can be exported.
I did all three in a minimal way, only changing the checks for
the specific case of a process (typically mountd) doing exports
within a vnet prison and not updating the mount point in other
ways. The changes are:
- Ignore the error return from vfs_suser(), since the file
system being mounted outside the prison will cause it to fail.
- Use the priv_check(PRIV_NFS_DAEMON) for this specific case
within a prison.
- Skip the call to VFS_MOUNT(), since it will return an error,
due to the "from" argument not being set correctly. VFS_MOUNT()
does not appear to do anything for the case of doing exports only.
(cherry picked from commit 4bbbd5875d32f3cbe76235d90243f713eff9b9d0)
---
sys/kern/vfs_mount.c | 107 ++++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 93 insertions(+), 14 deletions(-)
diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c
index 4c941c2616ff..e3a7ca50e792 100644
--- a/sys/kern/vfs_mount.c
+++ b/sys/kern/vfs_mount.c
@@ -76,7 +76,8 @@ __FBSDID("$FreeBSD$");
#define VFS_MOUNTARG_SIZE_MAX (1024 * 64)
static int vfs_domount(struct thread *td, const char *fstype, char *fspath,
- uint64_t fsflags, struct vfsoptlist **optlist);
+ uint64_t fsflags, bool jail_export,
+ struct vfsoptlist **optlist);
static void free_mntarg(struct mntarg *ma);
static int usermount = 0;
@@ -663,7 +664,7 @@ vfs_donmount(struct thread *td, uint64_t fsflags, struct
uio *fsoptions)
struct vfsopt *opt, *tmp_opt;
char *fstype, *fspath, *errmsg;
int error, fstypelen, fspathlen, errmsg_len, errmsg_pos;
- bool autoro;
+ bool autoro, has_nonexport, jail_export;
errmsg = fspath = NULL;
errmsg_len = fspathlen = 0;
@@ -699,15 +700,37 @@ vfs_donmount(struct thread *td, uint64_t fsflags, struct
uio *fsoptions)
goto bail;
}
+ /*
+ * Check to see that "export" is only used with the "update", "fstype",
+ * "fspath", "from" and "errmsg" options when in a vnet jail.
+ * These are the ones used to set/update exports by mountd(8).
+ * If only the above options are set in a jail that can run mountd(8),
+ * then the jail_export argument of vfs_domount() will be true.
+ * When jail_export is true, the vfs_suser() check does not cause
+ * failure, but limits the update to exports only.
+ * This allows mountd(8) running within the vnet jail
+ * to export file systems visible within the jail, but
+ * mounted outside of the jail.
+ */
/*
* We need to see if we have the "update" option
* before we call vfs_domount(), since vfs_domount() has special
* logic based on MNT_UPDATE. This is very important
* when we want to update the root filesystem.
*/
+ has_nonexport = false;
+ jail_export = false;
TAILQ_FOREACH_SAFE(opt, optlist, link, tmp_opt) {
int do_freeopt = 0;
+ if (jailed(td->td_ucred) &&
+ strcmp(opt->name, "export") != 0 &&
+ strcmp(opt->name, "update") != 0 &&
+ strcmp(opt->name, "fstype") != 0 &&
+ strcmp(opt->name, "fspath") != 0 &&
+ strcmp(opt->name, "from") != 0 &&
+ strcmp(opt->name, "errmsg") != 0)
+ has_nonexport = true;
if (strcmp(opt->name, "update") == 0) {
fsflags |= MNT_UPDATE;
do_freeopt = 1;
@@ -790,9 +813,10 @@ vfs_donmount(struct thread *td, uint64_t fsflags, struct
uio *fsoptions)
fsflags |= MNT_SYNCHRONOUS;
else if (strcmp(opt->name, "union") == 0)
fsflags |= MNT_UNION;
- else if (strcmp(opt->name, "export") == 0)
+ else if (strcmp(opt->name, "export") == 0) {
fsflags |= MNT_EXPORTED;
- else if (strcmp(opt->name, "automounted") == 0) {
+ jail_export = true;
+ } else if (strcmp(opt->name, "automounted") == 0) {
fsflags |= MNT_AUTOMOUNTED;
do_freeopt = 1;
} else if (strcmp(opt->name, "nocover") == 0) {
@@ -822,7 +846,15 @@ vfs_donmount(struct thread *td, uint64_t fsflags, struct
uio *fsoptions)
goto bail;
}
- error = vfs_domount(td, fstype, fspath, fsflags, &optlist);
+ /*
+ * If has_nonexport is true or the caller is not running within a
+ * vnet prison that can run mountd(8), set jail_export false.
+ */
+ if (has_nonexport || !jailed(td->td_ucred) ||
+ !prison_check_nfsd(td->td_ucred))
+ jail_export = false;
+
+ error = vfs_domount(td, fstype, fspath, fsflags, jail_export, &optlist);
if (error == ENOENT) {
error = EINVAL;
if (errmsg != NULL)
@@ -840,7 +872,8 @@ vfs_donmount(struct thread *td, uint64_t fsflags, struct
uio *fsoptions)
printf("%s: R/W mount failed, possibly R/O media,"
" trying R/O mount\n", __func__);
fsflags |= MNT_RDONLY;
- error = vfs_domount(td, fstype, fspath, fsflags, &optlist);
+ error = vfs_domount(td, fstype, fspath, fsflags, jail_export,
+ &optlist);
}
bail:
/* copyout the errmsg */
@@ -1114,6 +1147,7 @@ vfs_domount_update(
struct thread *td, /* Calling thread. */
struct vnode *vp, /* Mount point vnode. */
uint64_t fsflags, /* Flags common to all filesystems. */
+ bool jail_export, /* Got export option in vnet prison. */
struct vfsoptlist **optlist /* Options local to the filesystem. */
)
{
@@ -1125,6 +1159,7 @@ vfs_domount_update(
int error, export_error, i, len;
uint64_t flag;
gid_t *grps;
+ bool vfs_suser_failed;
ASSERT_VOP_ELOCKED(vp, __func__);
KASSERT((fsflags & MNT_UPDATE) != 0, ("MNT_UPDATE should be here"));
@@ -1153,7 +1188,20 @@ vfs_domount_update(
* Only privileged root, or (if MNT_USER is set) the user that
* did the original mount is permitted to update it.
*/
+ /*
+ * For the case of mountd(8) doing exports in a jail, the vfs_suser()
+ * call does not cause failure. vfs_domount() has already checked
+ * that "root" is doing this and vfs_suser() will fail when
+ * the file system has been mounted outside the jail.
+ * jail_export set true indicates that "export" is not mixed
+ * with other options that change mount behaviour.
+ */
+ vfs_suser_failed = false;
error = vfs_suser(mp, td);
+ if (jail_export && error != 0) {
+ error = 0;
+ vfs_suser_failed = true;
+ }
if (error != 0) {
vput(vp);
return (error);
@@ -1183,11 +1231,26 @@ vfs_domount_update(
error = EBUSY;
goto end;
}
- mp->mnt_flag &= ~MNT_UPDATEMASK;
- mp->mnt_flag |= fsflags & (MNT_RELOAD | MNT_FORCE | MNT_UPDATE |
- MNT_SNAPSHOT | MNT_ROOTFS | MNT_UPDATEMASK | MNT_RDONLY);
- if ((mp->mnt_flag & MNT_ASYNC) == 0)
- mp->mnt_kern_flag &= ~MNTK_ASYNC;
+ if (vfs_suser_failed) {
+ KASSERT((fsflags & (MNT_EXPORTED | MNT_UPDATE)) ==
+ (MNT_EXPORTED | MNT_UPDATE),
+ ("%s: jailed export did not set expected fsflags",
+ __func__));
+ /*
+ * For this case, only MNT_UPDATE and
+ * MNT_EXPORTED have been set in fsflags
+ * by the options. Only set MNT_UPDATE,
+ * since that is the one that would be set
+ * when set in fsflags, below.
+ */
+ mp->mnt_flag |= MNT_UPDATE;
+ } else {
+ mp->mnt_flag &= ~MNT_UPDATEMASK;
+ mp->mnt_flag |= fsflags & (MNT_RELOAD | MNT_FORCE | MNT_UPDATE |
+ MNT_SNAPSHOT | MNT_ROOTFS | MNT_UPDATEMASK | MNT_RDONLY);
+ if ((mp->mnt_flag & MNT_ASYNC) == 0)
+ mp->mnt_kern_flag &= ~MNTK_ASYNC;
+ }
rootvp = vfs_cache_root_clear(mp);
MNT_IUNLOCK(mp);
mp->mnt_optnew = *optlist;
@@ -1198,7 +1261,17 @@ vfs_domount_update(
* XXX The final recipients of VFS_MOUNT just overwrite the ndp they
* get. No freeing of cn_pnbuf.
*/
- error = VFS_MOUNT(mp);
+ /*
+ * For the case of mountd(8) doing exports from within a vnet jail,
+ * "from" is typically not set correctly such that VFS_MOUNT() will
+ * return ENOENT. It is not obvious that VFS_MOUNT() ever needs to be
+ * called when mountd is doing exports, but this check only applies to
+ * the specific case where it is running inside a vnet jail, to
+ * avoid any POLA violation.
+ */
+ error = 0;
+ if (!jail_export)
+ error = VFS_MOUNT(mp);
export_error = 0;
/* Process the export option. */
@@ -1336,6 +1409,7 @@ vfs_domount(
const char *fstype, /* Filesystem type. */
char *fspath, /* Mount path. */
uint64_t fsflags, /* Flags common to all filesystems. */
+ bool jail_export, /* Got export option in vnet prison. */
struct vfsoptlist **optlist /* Options local to the filesystem. */
)
{
@@ -1353,7 +1427,11 @@ vfs_domount(
if (strlen(fstype) >= MFSNAMELEN || strlen(fspath) >= MNAMELEN)
return (ENAMETOOLONG);
- if (jailed(td->td_ucred) || usermount == 0) {
+ if (jail_export) {
+ error = priv_check(td, PRIV_NFS_DAEMON);
+ if (error)
+ return (error);
+ } else if (jailed(td->td_ucred) || usermount == 0) {
if ((error = priv_check(td, PRIV_VFS_MOUNT)) != 0)
return (error);
}
@@ -1434,7 +1512,8 @@ vfs_domount(
}
free(pathbuf, M_TEMP);
} else
- error = vfs_domount_update(td, vp, fsflags, optlist);
+ error = vfs_domount_update(td, vp, fsflags, jail_export,
+ optlist);
out:
NDFREE(&nd, NDF_ONLY_PNBUF);
