CVE-2021-41133 (published 2021-10-08T14:15Z)

Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. In versions prior to 1.10.4 and 1.12.0, Flatpak apps with direct access to AF_UNIX sockets such as those used by Wayland, Pipewire or pipewire-pulse can trick portals and other host-OS services into treating the Flatpak app as though it was an ordinary, non-sandboxed host-OS process. They can do this by manipulating the VFS using recent mount-related syscalls that are not blocked by Flatpak's denylist seccomp filter, in order to substitute a crafted `/.flatpak-info` or make that file disappear entirely. Flatpak apps that act as clients for AF_UNIX sockets such as those used by Wayland, Pipewire or pipewire-pulse can escalate the privileges that the corresponding services will believe the Flatpak app has. Note that protocols that operate entirely over the D-Bus session bus (user bus), system bus or accessibility bus are not affected by this. This is due to the use of a proxy process `xdg-dbus-proxy`, whose VFS cannot be manipulated by the Flatpak app, when interacting with these buses. Patches exist for versions 1.10.4 and 1.12.0, and as of time of publication, a patch for version 1.8.2 is being planned. There are no workarounds aside from upgrading to a patched version.

Severity: MEDIUM
CVSS v2 base score: 4.6 (AV:L/AC:L/Au:N/C:P/I:P/A:P)
CVSS v3 base score: 7.8, HIGH (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)

Weakness information:
cwe_id: NVD-CWE-Other
cwe_name: Other
description: NVD is only using a subset of CWE for mapping instead of the entire CWE, and the weakness type is not covered by that subset.
extended_description: Insufficient Information

Fix information:
repo_url: https://github.com/flatpak/flatpak
commit_details: repo_url: https://github.com/flatpak/flatpak
author: Simon McVittie
author_date: 2021-09-01 14:20:29+01:00
msg: run: Don't allow unmounting filesystems

If we don't allow mounting filesystems, we shouldn't allow unmounting
either.

Partially fixes GHSA-67h7-w3jq-vh4q.

Signed-off-by: Simon McVittie <smcv@collabora.com>
repository: repo_url: https://github.com/flatpak/flatpak
repo_name: flatpak/flatpak
description: Linux application sandboxing and distribution framework
repo_language: C
owner: flatpak
file_changes: filename: flatpak-run.c
change_type: ModificationType.MODIFY
diff: @@ -2934,6 +2934,8 @@ setup_seccomp (FlatpakBwrap   *bwrap,
     {SCMP_SYS (unshare), EPERM},
     {SCMP_SYS (setns), EPERM},
     {SCMP_SYS (mount), EPERM},
+    {SCMP_SYS (umount), EPERM},
+    {SCMP_SYS (umount2), EPERM},
     {SCMP_SYS (pivot_root), EPERM},
 #if defined(__s390__) || defined(__s390x__) || defined(__CRIS__)
     /* Architectures with CONFIG_CLONE_BACKWARDS2: the child stack

programming_language: C
repo_url: https://github.com/flatpak/flatpak
commit_details: repo_url: https://github.com/flatpak/flatpak
author: Simon McVittie
author_date: 2021-09-01 11:59:00+01:00
msg: run: Block clone3() in sandbox

clone3() can be used to implement clone() with CLONE_NEWUSER, allowing
a sandboxed process to get CAP_SYS_ADMIN in a new namespace and
manipulate its root directory. We need to block this so that AF_UNIX-based
socket servers (X11, Wayland, etc.) can rely on
/proc/PID/root/.flatpak-info existing for all Flatpak-sandboxed apps.

Partially fixes GHSA-67h7-w3jq-vh4q.

Thanks: an anonymous reporter
Signed-off-by: Simon McVittie <smcv@collabora.com>
repository: repo_url: https://github.com/flatpak/flatpak
repo_name: flatpak/flatpak
description: Linux application sandboxing and distribution framework
repo_language: C
owner: flatpak
file_changes: filename: flatpak-run.c
change_type: ModificationType.MODIFY
diff: @@ -2945,6 +2945,12 @@ setup_seccomp (FlatpakBwrap   *bwrap,
 
     /* Don't allow faking input to the controlling tty (CVE-2017-5226) */
     {SCMP_SYS (ioctl), EPERM, &SCMP_A1 (SCMP_CMP_MASKED_EQ, 0xFFFFFFFFu, (int) TIOCSTI)},
+
+    /* seccomp can't look into clone3()'s struct clone_args to check whether
+     * the flags are OK, so we have no choice but to block clone3().
+     * Return ENOSYS so user-space will fall back to clone().
+     * (GHSA-67h7-w3jq-vh4q; see also https://github.com/moby/moby/commit/9f6b562d) */
+    {SCMP_SYS (clone3), ENOSYS},
   };
 
   struct

programming_language: C
repo_url: https://github.com/flatpak/flatpak
commit_details: repo_url: https://github.com/flatpak/flatpak
author: Simon McVittie
author_date: 2021-09-01 14:19:31+01:00
msg: run: Block setns()

If we don't allow unshare() or clone() with CLONE_NEWUSER, we also
shouldn't allow joining an existing (but different) namespace.

Partially fixes GHSA-67h7-w3jq-vh4q.

Signed-off-by: Simon McVittie <smcv@collabora.com>
repository: repo_url: https://github.com/flatpak/flatpak
repo_name: flatpak/flatpak
description: Linux application sandboxing and distribution framework
repo_language: C
owner: flatpak
file_changes: filename: flatpak-run.c
change_type: ModificationType.MODIFY
diff: @@ -2932,6 +2932,7 @@ setup_seccomp (FlatpakBwrap   *bwrap,
 
     /* Don't allow subnamespace setups: */
     {SCMP_SYS (unshare), EPERM},
+    {SCMP_SYS (setns), EPERM},
     {SCMP_SYS (mount), EPERM},
     {SCMP_SYS (pivot_root), EPERM},
 #if defined(__s390__) || defined(__s390x__) || defined(__CRIS__)

programming_language: C
repo_url: https://github.com/flatpak/flatpak
commit_details: repo_url: https://github.com/flatpak/flatpak
author: Simon McVittie
author_date: 2021-09-01 12:44:04+01:00
msg: run: Add cross-references for some other seccomp syscall filters

Signed-off-by: Simon McVittie <smcv@collabora.com>
repository: repo_url: https://github.com/flatpak/flatpak
repo_name: flatpak/flatpak
description: Linux application sandboxing and distribution framework
repo_language: C
owner: flatpak
file_changes: filename: flatpak-run.c
change_type: ModificationType.MODIFY
diff: @@ -2892,6 +2892,10 @@ setup_seccomp (FlatpakBwrap   *bwrap,
    *  https://git.gnome.org/browse/linux-user-chroot
    *    in src/setup-seccomp.c
    *
+   * Other useful resources:
+   * https://github.com/systemd/systemd/blob/HEAD/src/shared/seccomp-util.c
+   * https://github.com/moby/moby/blob/HEAD/profiles/seccomp/default.json
+   *
    **** END NOTE ON CODE SHARING
    */
   struct

programming_language: C
repo_url: https://github.com/flatpak/flatpak
commit_details: repo_url: https://github.com/flatpak/flatpak
author: Simon McVittie
author_date: 2021-09-01 14:21:04+01:00
msg: run: Don't allow chroot()

If we don't allow pivot_root() then there seems no reason why we should
allow chroot().

Partially fixes GHSA-67h7-w3jq-vh4q.

Signed-off-by: Simon McVittie <smcv@collabora.com>
repository: repo_url: https://github.com/flatpak/flatpak
repo_name: flatpak/flatpak
description: Linux application sandboxing and distribution framework
repo_language: C
owner: flatpak
file_changes: filename: flatpak-run.c
change_type: ModificationType.MODIFY
diff: @@ -2937,6 +2937,7 @@ setup_seccomp (FlatpakBwrap   *bwrap,
     {SCMP_SYS (umount), EPERM},
     {SCMP_SYS (umount2), EPERM},
     {SCMP_SYS (pivot_root), EPERM},
+    {SCMP_SYS (chroot), EPERM},
 #if defined(__s390__) || defined(__s390x__) || defined(__CRIS__)
     /* Architectures with CONFIG_CLONE_BACKWARDS2: the child stack
      * and flags arguments are reversed so the flags come second */

programming_language: C
repo_url: https://github.com/flatpak/flatpak
commit_details: repo_url: https://github.com/flatpak/flatpak
author: Simon McVittie
author_date: 2021-09-01 11:53:23+01:00
msg: run: Add an errno value to seccomp filters

At the moment, if we block a syscall we always make it fail with EPERM,
but this is risky: user-space libraries can start to use new replacements
for old syscalls at any time, and will often treat EPERM as a fatal error.
For new syscalls, we should make the syscall fail with ENOSYS, which is
indistinguishable from running on an older kernel and will cause fallback
to an older implementation, for example clone3() to clone().

In future we should probably move from EPERM to ENOSYS for some of the
syscalls we already block, but for now keep the status quo.

This is a prerequisite for fixing the vulnerability tracked as
GHSA-67h7-w3jq-vh4q.

Signed-off-by: Simon McVittie <smcv@collabora.com>
repository: repo_url: https://github.com/flatpak/flatpak
repo_name: flatpak/flatpak
description: Linux application sandboxing and distribution framework
repo_language: C
owner: flatpak
file_changes: filename: flatpak-run.c
change_type: ModificationType.MODIFY
diff: @@ -2897,61 +2897,63 @@ setup_seccomp (FlatpakBwrap   *bwrap,
   struct
   {
     int                  scall;
+    int                  errnum;
     struct scmp_arg_cmp *arg;
   } syscall_blocklist[] = {
     /* Block dmesg */
-    {SCMP_SYS (syslog)},
+    {SCMP_SYS (syslog), EPERM},
     /* Useless old syscall */
-    {SCMP_SYS (uselib)},
+    {SCMP_SYS (uselib), EPERM},
     /* Don't allow disabling accounting */
-    {SCMP_SYS (acct)},
+    {SCMP_SYS (acct), EPERM},
     /* 16-bit code is unnecessary in the sandbox, and modify_ldt is a
        historic source of interesting information leaks. */
-    {SCMP_SYS (modify_ldt)},
+    {SCMP_SYS (modify_ldt), EPERM},
     /* Don't allow reading current quota use */
-    {SCMP_SYS (quotactl)},
+    {SCMP_SYS (quotactl), EPERM},
 
     /* Don't allow access to the kernel keyring */
-    {SCMP_SYS (add_key)},
-    {SCMP_SYS (keyctl)},
-    {SCMP_SYS (request_key)},
+    {SCMP_SYS (add_key), EPERM},
+    {SCMP_SYS (keyctl), EPERM},
+    {SCMP_SYS (request_key), EPERM},
 
     /* Scary VM/NUMA ops */
-    {SCMP_SYS (move_pages)},
-    {SCMP_SYS (mbind)},
-    {SCMP_SYS (get_mempolicy)},
-    {SCMP_SYS (set_mempolicy)},
-    {SCMP_SYS (migrate_pages)},
+    {SCMP_SYS (move_pages), EPERM},
+    {SCMP_SYS (mbind), EPERM},
+    {SCMP_SYS (get_mempolicy), EPERM},
+    {SCMP_SYS (set_mempolicy), EPERM},
+    {SCMP_SYS (migrate_pages), EPERM},
 
     /* Don't allow subnamespace setups: */
-    {SCMP_SYS (unshare)},
-    {SCMP_SYS (mount)},
-    {SCMP_SYS (pivot_root)},
+    {SCMP_SYS (unshare), EPERM},
+    {SCMP_SYS (mount), EPERM},
+    {SCMP_SYS (pivot_root), EPERM},
 #if defined(__s390__) || defined(__s390x__) || defined(__CRIS__)
     /* Architectures with CONFIG_CLONE_BACKWARDS2: the child stack
      * and flags arguments are reversed so the flags come second */
-    {SCMP_SYS (clone), &SCMP_A1 (SCMP_CMP_MASKED_EQ, CLONE_NEWUSER, CLONE_NEWUSER)},
+    {SCMP_SYS (clone), EPERM, &SCMP_A1 (SCMP_CMP_MASKED_EQ, CLONE_NEWUSER, CLONE_NEWUSER)},
 #else
     /* Normally the flags come first */
-    {SCMP_SYS (clone), &SCMP_A0 (SCMP_CMP_MASKED_EQ, CLONE_NEWUSER, CLONE_NEWUSER)},
+    {SCMP_SYS (clone), EPERM, &SCMP_A0 (SCMP_CMP_MASKED_EQ, CLONE_NEWUSER, CLONE_NEWUSER)},
 #endif
 
     /* Don't allow faking input to the controlling tty (CVE-2017-5226) */
-    {SCMP_SYS (ioctl), &SCMP_A1 (SCMP_CMP_MASKED_EQ, 0xFFFFFFFFu, (int) TIOCSTI)},
+    {SCMP_SYS (ioctl), EPERM, &SCMP_A1 (SCMP_CMP_MASKED_EQ, 0xFFFFFFFFu, (int) TIOCSTI)},
   };
 
   struct
   {
     int                  scall;
+    int                  errnum;
     struct scmp_arg_cmp *arg;
   } syscall_nondevel_blocklist[] = {
     /* Profiling operations; we expect these to be done by tools from outside
      * the sandbox.  In particular perf has been the source of many CVEs.
      */
-    {SCMP_SYS (perf_event_open)},
+    {SCMP_SYS (perf_event_open), EPERM},
     /* Don't allow you to switch to bsd emulation or whatnot */
-    {SCMP_SYS (personality), &SCMP_A0 (SCMP_CMP_NE, allowed_personality)},
-    {SCMP_SYS (ptrace)}
+    {SCMP_SYS (personality), EPERM, &SCMP_A0 (SCMP_CMP_NE, allowed_personality)},
+    {SCMP_SYS (ptrace), EPERM}
   };
   /* Blocklist all but unix, inet, inet6 and netlink */
   struct
@@ -3035,10 +3037,14 @@ setup_seccomp (FlatpakBwrap   *bwrap,
   for (i = 0; i < G_N_ELEMENTS (syscall_blocklist); i++)
     {
       int scall = syscall_blocklist[i].scall;
+      int errnum = syscall_blocklist[i].errnum;
+
+      g_return_val_if_fail (errnum == EPERM || errnum == ENOSYS, FALSE);
+
       if (syscall_blocklist[i].arg)
-        r = seccomp_rule_add (seccomp, SCMP_ACT_ERRNO (EPERM), scall, 1, *syscall_blocklist[i].arg);
+        r = seccomp_rule_add (seccomp, SCMP_ACT_ERRNO (errnum), scall, 1, *syscall_blocklist[i].arg);
       else
-        r = seccomp_rule_add (seccomp, SCMP_ACT_ERRNO (EPERM), scall, 0);
+        r = seccomp_rule_add (seccomp, SCMP_ACT_ERRNO (errnum), scall, 0);
       if (r < 0 && r == -EFAULT /* unknown syscall */)
         return flatpak_fail_error (error, FLATPAK_ERROR_SETUP_FAILED, _("Failed to block syscall %d"), scall);
     }
@@ -3048,10 +3054,14 @@ setup_seccomp (FlatpakBwrap   *bwrap,
       for (i = 0; i < G_N_ELEMENTS (syscall_nondevel_blocklist); i++)
         {
           int scall = syscall_nondevel_blocklist[i].scall;
+          int errnum = syscall_nondevel_blocklist[i].errnum;
+
+          g_return_val_if_fail (errnum == EPERM || errnum == ENOSYS, FALSE);
+
           if (syscall_nondevel_blocklist[i].arg)
-            r = seccomp_rule_add (seccomp, SCMP_ACT_ERRNO (EPERM), scall, 1, *syscall_nondevel_blocklist[i].arg);
+            r = seccomp_rule_add (seccomp, SCMP_ACT_ERRNO (errnum), scall, 1, *syscall_nondevel_blocklist[i].arg);
           else
-            r = seccomp_rule_add (seccomp, SCMP_ACT_ERRNO (EPERM), scall, 0);
+            r = seccomp_rule_add (seccomp, SCMP_ACT_ERRNO (errnum), scall, 0);
 
           if (r < 0 && r == -EFAULT /* unknown syscall */)
             return flatpak_fail_error (error, FLATPAK_ERROR_SETUP_FAILED, _("Failed to block syscall %d"), scall);

programming_language: C
repo_url: https://github.com/flatpak/flatpak
commit_details: repo_url: https://github.com/flatpak/flatpak
author: Simon McVittie
author_date: 2021-09-01 14:17:04+01:00
msg: common: Add a list of recently-added Linux syscalls

Historically, syscalls could take arbitrarily-different values on
different architectures, but new syscalls are added with syscall numbers
that align on each architecture.

Signed-off-by: Simon McVittie <smcv@collabora.com>
repository: repo_url: https://github.com/flatpak/flatpak
repo_name: flatpak/flatpak
description: Linux application sandboxing and distribution framework
repo_language: C
owner: flatpak
file_changes: filename: Makefile.am.inc
change_type: ModificationType.MODIFY
diff: @@ -160,6 +160,7 @@ libflatpak_common_la_SOURCES = \
 	common/flatpak-remote.c \
 	common/flatpak-run-private.h \
 	common/flatpak-run.c \
+	common/flatpak-syscalls-private.h \
 	common/flatpak-transaction-private.h \
 	common/flatpak-transaction.c \
 	common/flatpak-transaction.h \

programming_language: Shell
filename: flatpak-run.c
change_type: ModificationType.MODIFY
diff: @@ -41,6 +41,8 @@
 #include <libmalcontent/malcontent.h>
 #endif
 
+#include "flatpak-syscalls-private.h"
+
 #ifdef ENABLE_SECCOMP
 #include <seccomp.h>
 #endif

programming_language: C
filename: flatpak-syscalls-private.h
change_type: ModificationType.ADD
diff: @@ -0,0 +1,197 @@
+/*
+ * Copyright 2021 Collabora Ltd.
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <sys/syscall.h>
+
+#if defined(_MIPS_SIM)
+# if _MIPS_SIM == _MIPS_SIM_ABI32
+#   define FLATPAK_MISSING_SYSCALL_BASE 4000
+# elif _MIPS_SIM == _MIPS_SIM_ABI64
+#   define FLATPAK_MISSING_SYSCALL_BASE 5000
+# elif _MIPS_SIM == _MIPS_SIM_NABI32
+#   define FLATPAK_MISSING_SYSCALL_BASE 6000
+# else
+#   error "Unknown MIPS ABI"
+# endif
+#endif
+
+#if defined(__ia64__)
+# define FLATPAK_MISSING_SYSCALL_BASE 1024
+#endif
+
+#if defined(__alpha__)
+# define FLATPAK_MISSING_SYSCALL_BASE 110
+#endif
+
+#if defined(__x86_64__) && defined(__ILP32__)
+# define FLATPAK_MISSING_SYSCALL_BASE 0x40000000
+#endif
+
+/*
+ * FLATPAK_MISSING_SYSCALL_BASE:
+ *
+ * Number to add to the syscall numbers of recently-added syscalls
+ * to get the appropriate syscall for the current ABI.
+ */
+#ifndef FLATPAK_MISSING_SYSCALL_BASE
+# define FLATPAK_MISSING_SYSCALL_BASE 0
+#endif
+
+#ifndef __NR_open_tree
+# define __NR_open_tree (FLATPAK_MISSING_SYSCALL_BASE + 428)
+#endif
+#ifndef __SNR_open_tree
+# define __SNR_open_tree __NR_open_tree
+#endif
+
+#ifndef __NR_move_mount
+# define __NR_move_mount (FLATPAK_MISSING_SYSCALL_BASE + 429)
+#endif
+#ifndef __SNR_move_mount
+# define __SNR_move_mount __NR_move_mount
+#endif
+
+#ifndef __NR_fsopen
+# define __NR_fsopen (FLATPAK_MISSING_SYSCALL_BASE + 430)
+#endif
+#ifndef __SNR_fsopen
+# define __SNR_fsopen __NR_fsopen
+#endif
+
+#ifndef __NR_fsconfig
+# define __NR_fsconfig (FLATPAK_MISSING_SYSCALL_BASE + 431)
+#endif
+#ifndef __SNR_fsconfig
+# define __SNR_fsconfig __NR_fsconfig
+#endif
+
+#ifndef __NR_fsmount
+# define __NR_fsmount (FLATPAK_MISSING_SYSCALL_BASE + 432)
+#endif
+#ifndef __SNR_fsmount
+# define __SNR_fsmount __NR_fsmount
+#endif
+
+#ifndef __NR_fspick
+# define __NR_fspick (FLATPAK_MISSING_SYSCALL_BASE + 433)
+#endif
+#ifndef __SNR_fspick
+# define __SNR_fspick __NR_fspick
+#endif
+
+#ifndef __NR_pidfd_open
+# define __NR_pidfd_open (FLATPAK_MISSING_SYSCALL_BASE + 434)
+#endif
+#ifndef __SNR_pidfd_open
+# define __SNR_pidfd_open __NR_pidfd_open
+#endif
+
+#ifndef __NR_clone3
+# define __NR_clone3 (FLATPAK_MISSING_SYSCALL_BASE + 435)
+#endif
+#ifndef __SNR_clone3
+# define __SNR_clone3 __NR_clone3
+#endif
+
+#ifndef __NR_close_range
+# define __NR_close_range (FLATPAK_MISSING_SYSCALL_BASE + 436)
+#endif
+#ifndef __SNR_close_range
+# define __SNR_close_range __NR_close_range
+#endif
+
+#ifndef __NR_openat2
+# define __NR_openat2 (FLATPAK_MISSING_SYSCALL_BASE + 437)
+#endif
+#ifndef __SNR_openat2
+# define __SNR_openat2 __NR_openat2
+#endif
+
+#ifndef __NR_pidfd_getfd
+# define __NR_pidfd_getfd (FLATPAK_MISSING_SYSCALL_BASE + 438)
+#endif
+#ifndef __SNR_pidfd_getfd
+# define __SNR_pidfd_getfd __NR_pidfd_getfd
+#endif
+
+#ifndef __NR_faccessat2
+# define __NR_faccessat2 (FLATPAK_MISSING_SYSCALL_BASE + 439)
+#endif
+#ifndef __SNR_faccessat2
+# define __SNR_faccessat2 __NR_faccessat2
+#endif
+
+#ifndef __NR_process_madvise
+# define __NR_process_madvise (FLATPAK_MISSING_SYSCALL_BASE + 440)
+#endif
+#ifndef __SNR_process_madvise
+# define __SNR_process_madvise __NR_process_madvise
+#endif
+
+#ifndef __NR_epoll_pwait2
+# define __NR_epoll_pwait2 (FLATPAK_MISSING_SYSCALL_BASE + 441)
+#endif
+#ifndef __SNR_epoll_pwait2
+# define __SNR_epoll_pwait2 __NR_epoll_pwait2
+#endif
+
+#ifndef __NR_mount_setattr
+# define __NR_mount_setattr (FLATPAK_MISSING_SYSCALL_BASE + 442)
+#endif
+#ifndef __SNR_mount_setattr
+# define __SNR_mount_setattr __NR_mount_setattr
+#endif
+
+#ifndef __NR_quotactl_fd
+# define __NR_quotactl_fd (FLATPAK_MISSING_SYSCALL_BASE + 443)
+#endif
+#ifndef __SNR_quotactl_fd
+# define __SNR_quotactl_fd __NR_quotactl_fd
+#endif
+
+#ifndef __NR_landlock_create_ruleset
+# define __NR_landlock_create_ruleset (FLATPAK_MISSING_SYSCALL_BASE + 444)
+#endif
+#ifndef __SNR_landlock_create_ruleset
+# define __SNR_landlock_create_ruleset __NR_landlock_create_ruleset
+#endif
+
+#ifndef __NR_landlock_add_rule
+# define __NR_landlock_add_rule (FLATPAK_MISSING_SYSCALL_BASE + 445)
+#endif
+#ifndef __SNR_landlock_add_rule
+# define __SNR_landlock_add_rule __NR_landlock_add_rule
+#endif
+
+#ifndef __NR_landlock_restrict_self
+# define __NR_landlock_restrict_self (FLATPAK_MISSING_SYSCALL_BASE + 446)
+#endif
+#ifndef __SNR_landlock_restrict_self
+# define __SNR_landlock_restrict_self __NR_landlock_restrict_self
+#endif
+
+#ifndef __NR_memfd_secret
+# define __NR_memfd_secret (FLATPAK_MISSING_SYSCALL_BASE + 447)
+#endif
+#ifndef __SNR_memfd_secret
+# define __SNR_memfd_secret __NR_memfd_secret
+#endif
+
+/* Last updated: Linux 5.14, syscall numbers < 448 */

programming_language: Ruby
repo_url: https://github.com/flatpak/flatpak
commit_details: repo_url: https://github.com/flatpak/flatpak
author: Simon McVittie
author_date: 2021-09-01 12:45:54+01:00
msg: run: Disallow recently-added mount-manipulation syscalls

If we don't allow mount() then we shouldn't allow these either.

Partially fixes GHSA-67h7-w3jq-vh4q.

Thanks: an anonymous reporter
Signed-off-by: Simon McVittie <smcv@collabora.com>
repository: repo_url: https://github.com/flatpak/flatpak
repo_name: flatpak/flatpak
description: Linux application sandboxing and distribution framework
repo_language: C
owner: flatpak
file_changes: filename: flatpak-run.c
change_type: ModificationType.MODIFY
diff: @@ -2951,6 +2951,18 @@ setup_seccomp (FlatpakBwrap   *bwrap,
      * Return ENOSYS so user-space will fall back to clone().
      * (GHSA-67h7-w3jq-vh4q; see also https://github.com/moby/moby/commit/9f6b562d) */
     {SCMP_SYS (clone3), ENOSYS},
+
+    /* New mount manipulation APIs can also change our VFS. There's no
+     * legitimate reason to do these in the sandbox, so block all of them
+     * rather than thinking about which ones might be dangerous.
+     * (GHSA-67h7-w3jq-vh4q) */
+    {SCMP_SYS (open_tree), ENOSYS},
+    {SCMP_SYS (move_mount), ENOSYS},
+    {SCMP_SYS (fsopen), ENOSYS},
+    {SCMP_SYS (fsconfig), ENOSYS},
+    {SCMP_SYS (fsmount), ENOSYS},
+    {SCMP_SYS (fspick), ENOSYS},
+    {SCMP_SYS (mount_setattr), ENOSYS},
   };
 
   struct

programming_language: C