From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout.kundenserver.de (mout.kundenserver.de [212.227.126.187]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DB5AF172BDE for ; Tue, 11 Jun 2024 08:43:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=212.227.126.187 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718095401; cv=none; b=kjLKvm4AqNd8MtDqHAoemgYahhr/Y9WHaU82ta5XPKhKZOOkWUhMd6+y3H4TWT1FhXUwag0r4pew1gLNFCjGSGlCNjmtxrkGkD4oQPRWArX8/UmCB9vwNtRfM8fHzVJnnOAL7g+Rn5t12bOzhV1/0+8QTwPN+VowofE6biOErPo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718095401; c=relaxed/simple; bh=LCATPotSz2ATRD7CPZiRXHBkg12fcf+9FklB+vEJs/4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ccehHF0POWKLVP7F4gGwIKLOpiELSd9u0ENGUdOKGN/zu2YCFwDA7e6rfCnICrpxdEEwSYtVJYZ2g8kNf9y1kAShkISlIJkETuWrJspnLxOLjqszZqwiIzFWOwyYspYCvUQAgxRMCEyQ1hgKlk+OjBAzlACDzgr0gq9xT1+jnRg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=vivier.eu; spf=pass smtp.mailfrom=vivier.eu; arc=none smtp.client-ip=212.227.126.187 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=vivier.eu Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=vivier.eu Received: from quad ([82.64.211.94]) by mrelayeu.kundenserver.de (mreue010 [212.227.15.167]) with ESMTPSA (Nemesis) id 1MY5wD-1ruEmM2MkH-00MYAP; Tue, 11 Jun 2024 10:43:15 +0200 From: Laurent Vivier To: util-linux@vger.kernel.org Cc: Laurent Vivier Subject: [PATCH v2 1/2] unshare: mount binfmt_misc Date: Tue, 11 Jun 2024 10:43:13 +0200 Message-ID: <20240611084314.183913-2-laurent@vivier.eu> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240611084314.183913-1-laurent@vivier.eu> References: <20240611084314.183913-1-laurent@vivier.eu> Precedence: bulk X-Mailing-List: util-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Provags-ID: V03:K1:1U7AGUJvNLuaOLgcGCBogxOodq3s9rnXHEAPbPA9xn5445oYm/9 oE6tdtMV5NvKralblOLEh6P5WdASiD42rGKFhaO2DJJ+RoJY3sS8Af4ym5ucMe/R7GPO0ZO Sj5rIG8M0ylvyPjC2jlhT1ajT1UqnIActz5iJ9yRg64JRYdrO9nnbQSsMk+/+yYgKUvLNLS nPoe7XhWvA+AjaKfYhhEQ== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:+3whv2728f4=;ihT51Y7Kvx58NWv+oxbR9ag6z14 DfgW87Be3teVDsfpeck4cUMxqpFiwXLiSv1eFvrfCreQ5SdP3IKcFMseZiSTiIc0zQQPamDu6 3fC28TE/o1ZKDTGrvpY4QYH9OjyHDpvlrjRgldju9fB/DvaXJW6rSEpsoIr1MzwvRvMYBtVvj 5EysSdXG5VWOxPPhrGRn9QpTFn/WwYaTe66va+bSyNRIOpq/+dehLHmmwIZxqSeFmxmoNQv2V HAnYY1B1JD7eKcTV8gIEWbw+Zx4SU4ZQoOPxOXsHdu0sSJrWaarYJqByy2TiSfidi863Vp06t 1lNoF9IQoLbhRZAD0vQx4gNBcvM3GyhTRheZMvZKXeIZYh3tJp4dJhUYufA5phQDHucgh5jfZ GrbDdnLNpPJxWYLvTRBy3lX5NNKRnEESjTNaOlsS5Jg7ennte8FedifT7GqVVcBIiUE+IOTn1 ycpuVFsp6BatoIv1uDQ+fnoMbl9+bOAC49aA/HGJ4GjWc2ikePmeVMrvhDKvjDomMx3WGQVAN yTa3XYuYe/hshJ4aOMck76mj25L6x7tr+4uZL2fZWl/pClw/v4g4gU0flKjZb2uHJkYpTLYZ9 4P61j1yDxt8whbAawxLxcuvQgv8I6xPbX78CEdIrFjocr/Lk68YmVNb7UOmZHtynCaju0sw0T Q1LfRKIr8xpr59UcAcch6ShI+CKMxKch6qdswTLme8iDywOCdE5UWHyqAWYovcj66nj1zj510 Xqeh7lCSal5OP4xxKLcKOfC6Yh9WkgsewQcSfJ0F3LkvIVlMUIQjiY= add --mount-binfmt[=] to mount binfmt_misc filesystem, this results in clearing inherited interpreters from the previous namespace Signed-off-by: Laurent Vivier --- 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[=] when dying, kill the forked child (implies --fork)\n" " defaults to SIGKILL\n"), out); fputs(_(" --mount-proc[=] mount proc filesystem first (implies --mount)\n"), out); + fputs(_(" --mount-binfmt[=] 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