add --mount-binfmt[=<dir>] to mount binfmt_misc filesystem, this results in clearing inherited interpreters from the previous namespace Signed-off-by: Laurent Vivier <laurent@xxxxxxxxx> --- Notes: v2: - remove definition of _PATH_PROC_BINFMT_MISC_REGISTER include/pathnames.h | 1 + sys-utils/unshare.1.adoc | 3 +++ sys-utils/unshare.c | 19 +++++++++++++++++++ 3 files changed, 23 insertions(+) diff --git a/include/pathnames.h b/include/pathnames.h index 81fa405f63c7..569bef17f982 100644 --- a/include/pathnames.h +++ b/include/pathnames.h @@ -204,6 +204,7 @@ /* sysctl fs paths */ #define _PATH_PROC_SYS_FS "/proc/sys/fs" #define _PATH_PROC_PIPE_MAX_SIZE _PATH_PROC_SYS_FS "/pipe-max-size" +#define _PATH_PROC_BINFMT_MISC _PATH_PROC_SYS_FS "/binfmt_misc" /* irqtop paths */ #define _PATH_PROC_INTERRUPTS "/proc/interrupts" diff --git a/sys-utils/unshare.1.adoc b/sys-utils/unshare.1.adoc index e6201e28fffd..48d1a5579282 100644 --- a/sys-utils/unshare.1.adoc +++ b/sys-utils/unshare.1.adoc @@ -90,6 +90,9 @@ When *unshare* terminates, have _signame_ be sent to the forked child process. C *--mount-proc*[**=**__mountpoint__]:: Just before running the program, mount the proc filesystem at _mountpoint_ (default is _/proc_). This is useful when creating a new PID namespace. It also implies creating a new mount namespace since the _/proc_ mount would otherwise mess up existing programs on the system. The new proc filesystem is explicitly mounted as private (with *MS_PRIVATE*|*MS_REC*). +*--mount-binfmt*[**=**__mountpoint__]:: +Just before running the program, mount the binfmt_misc filesystem at _mountpoint_ (default is /proc/sys/fs/binfmt_misc). It also implies creating a new mount namespace since the binfmt_misc mount would otherwise mess up existing programs on the system. The new binfmt_misc filesystem is explicitly mounted as private (with *MS_PRIVATE*|*MS_REC*). + **--map-user=**__uid|name__:: Run the program only after the current effective user ID has been mapped to _uid_. If this option is specified multiple times, the last occurrence takes precedence. This option implies *--user*. diff --git a/sys-utils/unshare.c b/sys-utils/unshare.c index 57f3b8744fb5..d79aa1125955 100644 --- a/sys-utils/unshare.c +++ b/sys-utils/unshare.c @@ -760,6 +760,7 @@ static void __attribute__((__noreturn__)) usage(void) fputs(_(" --kill-child[=<signame>] when dying, kill the forked child (implies --fork)\n" " defaults to SIGKILL\n"), out); fputs(_(" --mount-proc[=<dir>] mount proc filesystem first (implies --mount)\n"), out); + fputs(_(" --mount-binfmt[=<dir>] mount binfmt filesystem first (implies --user and --mount)\n"), out); fputs(_(" --propagation slave|shared|private|unchanged\n" " modify mount propagation in mount namespace\n"), out); fputs(_(" --setgroups allow|deny control the setgroups syscall in user namespaces\n"), out); @@ -783,6 +784,7 @@ int main(int argc, char *argv[]) { enum { OPT_MOUNTPROC = CHAR_MAX + 1, + OPT_MOUNTBINFMT, OPT_PROPAGATION, OPT_SETGROUPS, OPT_KILLCHILD, @@ -811,6 +813,7 @@ int main(int argc, char *argv[]) { "fork", no_argument, NULL, 'f' }, { "kill-child", optional_argument, NULL, OPT_KILLCHILD }, { "mount-proc", optional_argument, NULL, OPT_MOUNTPROC }, + { "mount-binfmt", optional_argument, NULL, OPT_MOUNTBINFMT }, { "map-user", required_argument, NULL, OPT_MAPUSER }, { "map-users", required_argument, NULL, OPT_MAPUSERS }, { "map-group", required_argument, NULL, OPT_MAPGROUP }, @@ -839,6 +842,7 @@ int main(int argc, char *argv[]) struct map_range *groupmap = NULL; int kill_child_signo = 0; /* 0 means --kill-child was not used */ const char *procmnt = NULL; + const char *binfmt_mnt = NULL; const char *newroot = NULL; const char *newdir = NULL; pid_t pid_bind = 0, pid_idmap = 0; @@ -913,6 +917,15 @@ int main(int argc, char *argv[]) unshare_flags |= CLONE_NEWNS; procmnt = optarg ? optarg : "/proc"; break; + case OPT_MOUNTBINFMT: + unshare_flags |= CLONE_NEWNS | CLONE_NEWUSER; + binfmt_mnt = optarg; + if (!binfmt_mnt) { + if (!procmnt) + procmnt = "/proc"; + binfmt_mnt = _PATH_PROC_BINFMT_MISC; + } + break; case OPT_MAPUSER: unshare_flags |= CLONE_NEWUSER; mapuser = get_user(optarg, _("failed to parse uid")); @@ -1178,6 +1191,12 @@ int main(int argc, char *argv[]) err(EXIT_FAILURE, _("mount %s failed"), procmnt); } + if (binfmt_mnt) { + if (mount("binfmt_misc", binfmt_mnt, "binfmt_misc", + MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL) != 0) + err(EXIT_FAILURE, _("mount %s failed"), binfmt_mnt); + } + if (force_gid) { if (setgroups(0, NULL) != 0) /* drop supplementary groups */ err(EXIT_FAILURE, _("setgroups failed")); -- 2.45.2