git: 5eeb4f737f11 - main - imgact_binmisc: Optionally pre-open the interpreter vnode
Date: Thu, 08 Dec 2022 14:32:35 UTC
The branch main has been updated by dfr:
URL: https://cgit.FreeBSD.org/src/commit/?id=5eeb4f737f11b253ac330ae459b05e30fd16d0e8
commit 5eeb4f737f11b253ac330ae459b05e30fd16d0e8
Author: Doug Rabson <dfr@FreeBSD.org>
AuthorDate: 2022-11-17 10:48:20 +0000
Commit: Doug Rabson <dfr@FreeBSD.org>
CommitDate: 2022-12-08 14:32:03 +0000
imgact_binmisc: Optionally pre-open the interpreter vnode
This allows the use of chroot and/or jail environments which depend on
interpreters registed with imgact_binmisc to use emulator binaries from
the host to emulate programs inside the chroot.
Reviewed by: imp
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D37432
---
sys/kern/imgact_binmisc.c | 49 ++++++++++++++++++++++++++++++++++++----
sys/kern/kern_exec.c | 18 ++++++++++++++-
sys/sys/imgact.h | 1 +
sys/sys/imgact_binmisc.h | 3 ++-
usr.sbin/binmiscctl/binmiscctl.8 | 8 +++++++
usr.sbin/binmiscctl/binmiscctl.c | 15 ++++++++----
6 files changed, 83 insertions(+), 11 deletions(-)
diff --git a/sys/kern/imgact_binmisc.c b/sys/kern/imgact_binmisc.c
index 951822df06b1..65b2e8e409a6 100644
--- a/sys/kern/imgact_binmisc.c
+++ b/sys/kern/imgact_binmisc.c
@@ -30,15 +30,18 @@ __FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/ctype.h>
#include <sys/exec.h>
+#include <sys/fcntl.h>
#include <sys/imgact.h>
#include <sys/imgact_binmisc.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
+#include <sys/namei.h>
#include <sys/sbuf.h>
#include <sys/sysctl.h>
#include <sys/sx.h>
+#include <sys/vnode.h>
#include <machine/atomic.h>
@@ -63,6 +66,7 @@ typedef struct imgact_binmisc_entry {
uint8_t *ibe_magic;
uint8_t *ibe_mask;
uint8_t *ibe_interpreter;
+ struct vnode *ibe_interpreter_vnode;
ssize_t ibe_interp_offset;
uint32_t ibe_interp_argcnt;
uint32_t ibe_interp_length;
@@ -114,7 +118,7 @@ static struct sx interp_list_sx;
* Populate the entry with the information about the interpreter.
*/
static void
-imgact_binmisc_populate_interp(char *str, imgact_binmisc_entry_t *ibe)
+imgact_binmisc_populate_interp(char *str, imgact_binmisc_entry_t *ibe, int flags)
{
uint32_t len = 0, argc = 1;
char t[IBE_INTERP_LEN_MAX];
@@ -150,6 +154,30 @@ imgact_binmisc_populate_interp(char *str, imgact_binmisc_entry_t *ibe)
memcpy(ibe->ibe_interpreter, t, len);
ibe->ibe_interp_argcnt = argc;
ibe->ibe_interp_length = len;
+
+ ibe->ibe_interpreter_vnode = NULL;
+ if (flags & IBF_PRE_OPEN) {
+ struct nameidata nd;
+ int error;
+
+ tp = t;
+ while (*tp != '\0' && *tp != ' ') {
+ tp++;
+ }
+ *tp = '\0';
+ NDINIT(&nd, LOOKUP, FOLLOW | ISOPEN, UIO_SYSSPACE, t);
+
+ /*
+ * If there is an error, just stop now and fall back
+ * to the non pre-open case where we lookup during
+ * exec.
+ */
+ error = namei(&nd);
+ if (error)
+ return;
+
+ ibe->ibe_interpreter_vnode = nd.ni_vp;
+ }
}
/*
@@ -167,7 +195,7 @@ imgact_binmisc_new_entry(ximgact_binmisc_entry_t *xbe, ssize_t interp_offset,
ibe->ibe_name = malloc(namesz, M_BINMISC, M_WAITOK|M_ZERO);
strlcpy(ibe->ibe_name, xbe->xbe_name, namesz);
- imgact_binmisc_populate_interp(xbe->xbe_interpreter, ibe);
+ imgact_binmisc_populate_interp(xbe->xbe_interpreter, ibe, xbe->xbe_flags);
ibe->ibe_magic = malloc(xbe->xbe_msize, M_BINMISC, M_WAITOK|M_ZERO);
memcpy(ibe->ibe_magic, xbe->xbe_magic, xbe->xbe_msize);
@@ -199,6 +227,8 @@ imgact_binmisc_destroy_entry(imgact_binmisc_entry_t *ibe)
free(ibe->ibe_interpreter, M_BINMISC);
if (ibe->ibe_name)
free(ibe->ibe_name, M_BINMISC);
+ if (ibe->ibe_interpreter_vnode)
+ vrele(ibe->ibe_interpreter_vnode);
if (ibe)
free(ibe, M_BINMISC);
}
@@ -271,15 +301,20 @@ imgact_binmisc_add_entry(ximgact_binmisc_entry_t *xbe)
}
}
+ /*
+ * Preallocate a new entry. We do this without holding the
+ * lock to avoid lock-order problems if IBF_PRE_OPEN is
+ * set.
+ */
+ ibe = imgact_binmisc_new_entry(xbe, interp_offset, argv0_cnt);
+
INTERP_LIST_WLOCK();
if (imgact_binmisc_find_entry(xbe->xbe_name) != NULL) {
INTERP_LIST_WUNLOCK();
+ imgact_binmisc_destroy_entry(ibe);
return (EEXIST);
}
- /* Preallocate a new entry. */
- ibe = imgact_binmisc_new_entry(xbe, interp_offset, argv0_cnt);
-
SLIST_INSERT_HEAD(&interpreter_list, ibe, link);
interp_list_entry_count++;
INTERP_LIST_WUNLOCK();
@@ -698,6 +733,10 @@ imgact_binmisc_exec(struct image_params *imgp)
/* Catch ibe->ibe_argv0_cnt counting more #a than we did. */
MPASS(ibe->ibe_argv0_cnt == argv0_cnt);
imgp->interpreter_name = imgp->args->begin_argv;
+ if (ibe->ibe_interpreter_vnode) {
+ imgp->interpreter_vp = ibe->ibe_interpreter_vnode;
+ vref(imgp->interpreter_vp);
+ }
done:
INTERP_LIST_RUNLOCK();
diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c
index cb45d18fbb85..68dab42c25cc 100644
--- a/sys/kern/kern_exec.c
+++ b/sys/kern/kern_exec.c
@@ -504,6 +504,18 @@ interpret:
imgp->execpath = args->fname;
vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
}
+ } else if (imgp->interpreter_vp) {
+ /*
+ * An image activator has already provided an open vnode
+ */
+ newtextvp = imgp->interpreter_vp;
+ imgp->interpreter_vp = NULL;
+ if (vn_fullpath(newtextvp, &imgp->execpath,
+ &imgp->freepath) != 0)
+ imgp->execpath = args->fname;
+ vn_lock(newtextvp, LK_SHARED | LK_RETRY);
+ AUDIT_ARG_VNODE1(newtextvp);
+ imgp->vp = newtextvp;
} else {
AUDIT_ARG_FD(args->fd);
@@ -702,7 +714,11 @@ interpret:
free(imgp->freepath, M_TEMP);
imgp->freepath = NULL;
/* set new name to that of the interpreter */
- args->fname = imgp->interpreter_name;
+ if (imgp->interpreter_vp) {
+ args->fname = NULL;
+ } else {
+ args->fname = imgp->interpreter_name;
+ }
goto interpret;
}
diff --git a/sys/sys/imgact.h b/sys/sys/imgact.h
index 0be3e71604bf..963f53aa387b 100644
--- a/sys/sys/imgact.h
+++ b/sys/sys/imgact.h
@@ -94,6 +94,7 @@ struct image_params {
u_int map_flags;
#define IMGP_ASLR_SHARED_PAGE 0x1
uint32_t imgp_flags;
+ struct vnode *interpreter_vp; /* vnode of the interpreter */
};
#ifdef _KERNEL
diff --git a/sys/sys/imgact_binmisc.h b/sys/sys/imgact_binmisc.h
index 74ff68622075..37ae9dcdd774 100644
--- a/sys/sys/imgact_binmisc.h
+++ b/sys/sys/imgact_binmisc.h
@@ -57,8 +57,9 @@ _Static_assert(IBE_MAGIC_MAX <= IBE_MATCH_MAX,
*/
#define IBF_ENABLED 0x0001 /* Entry is active. */
#define IBF_USE_MASK 0x0002 /* Use mask on header magic field. */
+#define IBF_PRE_OPEN 0x0004 /* Cache the vnode for interpreter */
-#define IBF_VALID_UFLAGS 0x0003 /* Bits allowed from userland. */
+#define IBF_VALID_UFLAGS 0x0007 /* Bits allowed from userland. */
/*
* Used with sysctlbyname() to pass imgact bin misc entries in and out of the
diff --git a/usr.sbin/binmiscctl/binmiscctl.8 b/usr.sbin/binmiscctl/binmiscctl.8
index 82624cccd9ed..198997d22058 100644
--- a/usr.sbin/binmiscctl/binmiscctl.8
+++ b/usr.sbin/binmiscctl/binmiscctl.8
@@ -46,6 +46,7 @@
.Op Fl -mask Ar mask
.Op Fl -offset Ar offset
.Op Fl -set-enabled
+.Op Fl -pre-open
.Nm
.Cm disable
.Ar name
@@ -87,6 +88,7 @@ Operation must be one of the following:
.Op Fl -mask Ar mask
.Op Fl -offset Ar offset
.Op Fl -set-enabled
+.Op Fl -pre-open
.Xc
Add a new activator entry in the kernel.
You must specify a
@@ -124,6 +126,12 @@ To enable the activator entry the
option is used.
The activator default state is disabled.
.Pp
+To make the interpreter automatically available in jails and chroots,
+use the
+.Fl -pre-open
+option to allow the kernel to open the binary at configuration time
+rather then lazily when the the interpreted program is started.
+.Pp
The interpreter
.Ar path
may also contain arguments for the interpreter including
diff --git a/usr.sbin/binmiscctl/binmiscctl.c b/usr.sbin/binmiscctl/binmiscctl.c
index 3c5e19def67b..2ec2cc3f64d4 100644
--- a/usr.sbin/binmiscctl/binmiscctl.c
+++ b/usr.sbin/binmiscctl/binmiscctl.c
@@ -75,7 +75,8 @@ static const struct {
"<name> --interpreter <path_and_arguments> \\\n"
"\t\t--magic <magic_bytes> [--mask <mask_bytes>] \\\n"
"\t\t--size <magic_size> [--offset <magic_offset>] \\\n"
- "\t\t[--set-enabled]"
+ "\t\t[--set-enabled] \\\n"
+ "\t\t[--pre-open]"
},
{
CMD_REMOVE,
@@ -122,6 +123,7 @@ add_opts[] = {
{ "magic", required_argument, NULL, 'm' },
{ "offset", required_argument, NULL, 'o' },
{ "size", required_argument, NULL, 's' },
+ { "pre-open", no_argument, NULL, 'p' },
{ NULL, 0, NULL, 0 }
};
@@ -192,8 +194,9 @@ printxbe(ximgact_binmisc_entry_t *xbe)
printf("name: %s\n", xbe->xbe_name);
printf("interpreter: %s\n", xbe->xbe_interpreter);
- printf("flags: %s%s\n", (flags & IBF_ENABLED) ? "ENABLED " : "",
- (flags & IBF_USE_MASK) ? "USE_MASK " : "");
+ printf("flags: %s%s%s\n", (flags & IBF_ENABLED) ? "ENABLED " : "",
+ (flags & IBF_USE_MASK) ? "USE_MASK " : "",
+ (flags & IBF_PRE_OPEN) ? "PRE_OPEN " : "");
printf("magic size: %u\n", xbe->xbe_msize);
printf("magic offset: %u\n", xbe->xbe_moffset);
@@ -291,7 +294,7 @@ add_cmd(__unused int argc, char *argv[], ximgact_binmisc_entry_t *xbe)
IBE_NAME_MAX);
strlcpy(&xbe->xbe_name[0], argv[0], IBE_NAME_MAX);
- while ((ch = getopt_long(argc, argv, "ei:m:M:o:s:", add_opts, NULL))
+ while ((ch = getopt_long(argc, argv, "epi:m:M:o:s:", add_opts, NULL))
!= -1) {
switch(ch) {
@@ -328,6 +331,10 @@ add_cmd(__unused int argc, char *argv[], ximgact_binmisc_entry_t *xbe)
xbe->xbe_msize);
break;
+ case 'p':
+ xbe->xbe_flags |= IBF_PRE_OPEN;
+ break;
+
default:
usage("Unknown argument: '%c'", ch);
}