On 12/8/22, Doug Rabson <[email protected]> wrote:
> The branch main has been updated by dfr:
>
> URL:
> https://cgit.FreeBSD.org/src/commit/?id=5eeb4f737f11b253ac330ae459b05e30fd16d0e8
>
> commit 5eeb4f737f11b253ac330ae459b05e30fd16d0e8
> Author: Doug Rabson <[email protected]>
> AuthorDate: 2022-11-17 10:48:20 +0000
> Commit: Doug Rabson <[email protected]>
> 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;
you need to add NDFREE_PNBUF(&nd)
> +
> + 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);
> }
>
--
Mateusz Guzik <mjguzik gmail.com>
