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Bug 730540 - sys-apps/file[seccomp]: Bad system call: Need ALLOW_RULE entries for 'writev' and 'statx' on musl libc
Summary: sys-apps/file[seccomp]: Bad system call: Need ALLOW_RULE entries for 'writev'...
Status: RESOLVED FIXED
Alias: None
Product: Gentoo Linux
Classification: Unclassified
Component: Current packages (show other bugs)
Hardware: All Linux
: Normal normal (vote)
Assignee: Gentoo musl team
URL:
Whiteboard:
Keywords:
Depends on:
Blocks:
 
Reported: 2020-07-03 08:17 UTC by 12101111
Modified: 2020-09-07 16:57 UTC (History)
4 users (show)

See Also:
Package list:
Runtime testing required: ---


Attachments
Patch for file-5.39 to add ALLOW_RULE entries for 'statx' and 'writev' (file-539-musl-seccomp-bad-syscalls.patch,619 bytes, patch)
2020-07-19 20:33 UTC, Joshua Kinard
Details | Diff

Note You need to log in before you can comment on or make changes to this bug.
Description 12101111 2020-07-03 08:17:27 UTC
strace of `./file` command:
......
brk(NULL)                               = 0x55cec680b000
brk(0x55cec680c000)                     = 0x55cec680c000
brk(0x55cec680d000)                     = 0x55cec680d000
brk(0x55cec680e000)                     = 0x55cec680e000
brk(0x55cec680f000)                     = 0x55cec680f000
prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)  = 0
seccomp(SECCOMP_SET_MODE_STRICT, 1, NULL) = -1 EINVAL (Invalid argument)
seccomp(SECCOMP_SET_MODE_FILTER, 0, 0x7faa4aadc680) = 0
stat(0x7faa4ab54020, 0x7ffc5216eef0)    = -1 ENOENT (No such file or directory)
stat(0x7faa4ab54020, 0x7ffc5216eef0)    = -1 ENOENT (No such file or directory)
open(0x7faa4aaa94a0, O_RDONLY)          = -1 ENOENT (No such file or directory)
stat(0x7faa4ab54020, 0x7ffc5216ee80)    = -1 ENOENT (No such file or directory)
open(0x7faa4ab54020, O_RDONLY)          = -1 ENOENT (No such file or directory)
sys-apps/file[seccomp]
writev(2, 0x7ffc5216ee40, 2)            = ?
+++ killed by SIGSYS +++
zsh: invalid system call  strace ./file

gdb with "catch syscall":
...
Catchpoint 1 (call to syscall 10), __mprotect (addr=<optimized out>, len=<optimized out>, prot=<optimized out>)
    at src/mman/mprotect.c:10
10	src/mman/mprotect.c: No such file or directory.
(gdb) c
Continuing.

Catchpoint 1 (returned from syscall 10), __mprotect (addr=<optimized out>, len=<optimized out>, prot=<optimized out>)
    at src/mman/mprotect.c:10
10	in src/mman/mprotect.c
(gdb)
Continuing.

Catchpoint 1 (call to syscall 20), __stdio_write (f=0x7ffff7ffbd18 <__stderr_FILE>, buf=<optimized out>, len=244)
    at src/stdio/__stdio_write.c:15
15	src/stdio/__stdio_write.c: No such file or directory.
(gdb) c
Continuing.

Program terminated with signal SIGSYS, Bad system call.
The program no longer exists.

musl's __stdio_write.c have the following code:
size_t __stdio_write(FILE *f, const unsigned char *buf, size_t len)
{
        struct iovec iovs[2] = {
                { .iov_base = f->wbase, .iov_len = f->wpos-f->wbase },
                { .iov_base = (void *)buf, .iov_len = len }
        };
        struct iovec *iov = iovs;
        size_t rem = iov[0].iov_len + iov[1].iov_len;
        int iovcnt = 2;
        ssize_t cnt;
        for (;;) {
                cnt = syscall(SYS_writev, f->fd, iov, iovcnt);
                if (cnt == rem) {
                        f->wend = f->buf + f->buf_size;
                        f->wpos = f->wbase = f->buf;
                        return len;
                }
                if (cnt < 0) {
                        f->wpos = f->wbase = f->wend = 0;
                        f->flags |= F_ERR;
                        return iovcnt == 2 ? 0 : len-iov[0].iov_len;
                }
                rem -= cnt;
                if (cnt > iov[0].iov_len) {
                        cnt -= iov[0].iov_len;
                        iov++; iovcnt--;
                }
                iov[0].iov_base = (char *)iov[0].iov_base + cnt;
                iov[0].iov_len -= cnt;
        }
}

But file's seccomp.c don't put "writev" in allow list. Add "writev" into allow list fix this issue:

diff --git a/src/seccomp.c b/src/seccomp.c
index 68c56485..aee9e957 100644
--- a/src/seccomp.c
+++ b/src/seccomp.c
@@ -226,6 +226,7 @@ enable_sandbox_full(void)
        ALLOW_RULE(getpid);     // Used by glibc in file_pipe2file()
        ALLOW_RULE(unlink);
        ALLOW_RULE(write);
+       ALLOW_RULE(writev);


 #if 0


Reproducible: Always

Steps to Reproduce:
1.emerge sys-apps/file on musl system
2.run `file` command
3.
Actual Results:  
bash: Bad system call
zsh: invalid system call

Expected Results:  
show file's usage

Portage 2.3.103 (python 3.8.3-final-0, default/linux/amd64/17.0/musl, gcc-10.0.0, musl-1.2.0-r1, 5.7.7-zen+ x86_64)
=================================================================
System uname: Linux-5.7.7-zen+-x86_64-Intel-R-_Core-TM-_i9-10900K_CPU_@_3.70GHz-with-libc
KiB Mem:   131716948 total, 123726324 free
KiB Swap:   16777212 total,  16777212 free
Timestamp of repository gentoo: Thu, 02 Jul 2020 23:05:28 +0000
Head commit of repository gentoo: 21cdbb1d04a3040cdb4ed91c72c6dea4055c23c4

Timestamp of repository gentoo-zh: Thu, 02 Jul 2020 08:38:54 +0000
Head commit of repository gentoo-zh: 02359beb21d1c5fa591e297e8521980144503c34

Timestamp of repository jorgicio: Thu, 02 Jul 2020 08:38:58 +0000
Head commit of repository jorgicio: 8bd01f2783805f8a0d07cd5a9b2d2ebb4b5bfbb2

Timestamp of repository lanodanOverlay: Thu, 02 Jul 2020 08:39:24 +0000
Head commit of repository lanodanOverlay: c12852dcc8315c6e74b8f24b004519a9e14f4b29

Timestamp of repository lto-overlay: Thu, 02 Jul 2020 14:35:12 +0000
Head commit of repository lto-overlay: 2da6204db51fb955ffddfb021b54a96980d87f24

Timestamp of repository musl: Thu, 02 Jul 2020 08:39:02 +0000
Head commit of repository musl: e6936b8b4d99a8a1e24cfd23fac8c59927c0a28b

Timestamp of repository mv: Thu, 02 Jul 2020 08:39:02 +0000
Head commit of repository mv: 4932a916b610979237f80f555cb58b579098e5b5

Timestamp of repository sorrow: Thu, 02 Jul 2020 14:05:17 +0000
Head commit of repository sorrow: 2d7ed9e21d5817ced16e4e1429c2a9fbfb6e4d8b

sh bash 5.0_p17
ld LLD 10.0.0 (compatible with GNU linkers)
ccache version 3.7.10 [enabled]
app-shells/bash:          5.0_p17::gentoo
dev-java/java-config:     2.3.1::gentoo
dev-lang/perl:            5.30.3-r1::gentoo
dev-lang/python:          2.7.18-r100::lto-overlay, 3.7.8::gentoo, 3.8.3-r1::lto-overlay
dev-util/ccache:          3.7.10::gentoo
dev-util/cmake:           3.17.3::gentoo
dev-util/pkgconfig:       0.29.2::gentoo
sys-apps/baselayout:      2.7::gentoo
sys-apps/openrc:          0.42.1::gentoo
sys-apps/sandbox:         2.20::gentoo
sys-devel/autoconf:       2.13-r1::gentoo, 2.69-r5::gentoo
sys-devel/automake:       1.16.2::gentoo
sys-devel/binutils:       2.34::12101111-overlay
sys-devel/libtool:        2.4.6-r6::gentoo
sys-devel/make:           4.2.1-r4::gentoo
sys-kernel/linux-headers: 5.7::gentoo (virtual/os-headers)
sys-libs/musl:            1.2.0-r1::gentoo
Repositories:

gentoo
    location: /usr/portage/gentoo
    sync-type: git
    sync-uri: https://github.com/gentoo-mirror/gentoo
    priority: -1000

12101111-overlay
    location: /usr/portage/local
    masters: gentoo

gentoo-zh
    location: /usr/portage/gentoo-zh
    sync-type: git
    sync-uri: https://github.com/gentoo-mirror/gentoo-zh.git
    masters: gentoo

jorgicio
    location: /usr/portage/jorgicio
    sync-type: git
    sync-uri: https://github.com/gentoo-mirror/jorgicio.git
    masters: gentoo

lanodanOverlay
    location: /usr/portage/lanodanOverlay
    sync-type: git
    sync-uri: https://github.com/gentoo-mirror/lanodanOverlay.git
    masters: gentoo

lto-overlay
    location: /usr/portage/lto-overlay
    sync-type: git
    sync-uri: https://github.com/gentoo-mirror/lto-overlay.git
    masters: gentoo mv

musl
    location: /usr/portage/musl
    sync-type: git
    sync-uri: https://github.com/gentoo-mirror/musl.git
    masters: gentoo

mv
    location: /usr/portage/mv
    sync-type: git
    sync-uri: https://github.com/gentoo-mirror/mv.git
    masters: gentoo

sorrow
    location: /usr/portage/sorrow
    sync-type: git
    sync-uri: https://github.com/gentoo-mirror/sorrow.git
    masters: gentoo

Installed sets: @fcitx5
ACCEPT_KEYWORDS="amd64 ~amd64"
ACCEPT_LICENSE="@FREE @BINARY-REDISTRIBUTABLE"
CBUILD="x86_64-gentoo-linux-musl"
CC="clang"
CFLAGS="-march=skylake -mtune=skylake -O3 -pipe -falign-functions=32 -fomit-frame-pointer -ffunction-sections -fdata-sections -flto=thin"
CHOST="x86_64-gentoo-linux-musl"
CONFIG_PROTECT="/etc /usr/share/config /usr/share/gnupg/qualified.txt"
CONFIG_PROTECT_MASK="/etc/ca-certificates.conf /etc/dconf /etc/env.d /etc/fonts/fonts.conf /etc/gconf /etc/gentoo-release /etc/revdep-rebuild /etc/sandbox.d /etc/terminfo"
CXX="clang++"
CXXFLAGS="-march=skylake -mtune=skylake -O3 -pipe -falign-functions=32 -fomit-frame-pointer -ffunction-sections -fdata-sections -flto=thin -stdlib=libc++"
DISTDIR="/var/cache/distfiles"
ENV_UNSET="DBUS_SESSION_BUS_ADDRESS DISPLAY GOBIN GOPATH PERL5LIB PERL5OPT PERLPREFIX PERL_CORE PERL_MB_OPT PERL_MM_OPT XAUTHORITY XDG_CACHE_HOME XDG_CONFIG_HOME XDG_DATA_HOME XDG_RUNTIME_DIR"
FCFLAGS="-O2 -pipe"
FEATURES="assume-digests binpkg-docompress binpkg-dostrip binpkg-logs buildpkg ccache config-protect-if-modified distlocks downgrade-backup ebuild-locks fixlafiles ipc-sandbox merge-sync network-sandbox news parallel-fetch pid-sandbox preserve-libs protect-owned qa-unresolved-soname-deps sandbox sfperms strict unknown-features-warn unmerge-logs unmerge-orphans userfetch userpriv usersandbox usersync xattr"
FFLAGS="-O2 -pipe"
GENTOO_MIRRORS="https://mirrors.tuna.tsinghua.edu.cn/gentoo"
INSTALL_MASK="charset.alias locale.alias"
LANG="zh_CN.UTF-8"
LC_ALL="zh_CN.UTF-8"
LDFLAGS="-fuse-ld=lld -rtlib=compiler-rt -unwindlib=libunwind -flto=thin -Wl,-O3 -Wl,--gc-sections -march=skylake -mtune=skylake"
MAKEOPTS="-j20"
PKGDIR="/var/cache/binpkgs"
PORTAGE_CONFIGROOT="/"
PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --omit-dir-times --compress --force --whole-file --delete --stats --human-readable --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages --exclude=/.git"
PORTAGE_TMPDIR="/var/tmp"
USE="X acl alsa amd64 bzip2 clang cli compiler-rt crypt default-compiler-rt default-libcxx dri elogind fortran gif iconv ipv6 jpeg libcxx libcxxabi libtirpc libunwind ncurses nls nptl opengl openmp pam pcre png readline seccomp split-usr ssl svg tcpd unicode vaapi vulkan wayland xattr zlib zsh-completion" ABI_X86="64" ADA_TARGET="gnat_2018" ALSA_CARDS="hda-intel usb-audio" APACHE2_MODULES="authn_core authz_core socache_shmcb unixd actions alias auth_basic authn_alias authn_anon authn_dbm authn_default authn_file authz_dbm authz_default authz_groupfile authz_host authz_owner authz_user autoindex cache cgi cgid dav dav_fs dav_lock deflate dir disk_cache env expires ext_filter file_cache filter headers include info log_config logio mem_cache mime mime_magic negotiation rewrite setenvif speling status unique_id userdir usertrack vhost_alias" CALLIGRA_FEATURES="karbon sheets words" COLLECTD_PLUGINS="df interface irq load memory rrdtool swap syslog" CPU_FLAGS_X86="aes avx avx2 f16c fma3 mmx mmxext pclmul popcnt sse sse2 sse3 sse4_1 sse4_2 ssse3" ELIBC="musl" GPSD_PROTOCOLS="ashtech aivdm earthmate evermore fv18 garmin garmintxt gpsclock greis isync itrax mtk3301 nmea ntrip navcom oceanserver oldstyle oncore rtcm104v2 rtcm104v3 sirf skytraq superstar2 timing tsip tripmate tnt ublox ubx" INPUT_DEVICES="libinput" KERNEL="linux" L10N="zh-CN" LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb ncurses text" LIBREOFFICE_EXTENSIONS="presenter-console presenter-minimizer" LLVM_TARGETS="X86 ARM AArch64 RISCV WebAssembly" OFFICE_IMPLEMENTATION="libreoffice" PHP_TARGETS="php7-4" POSTGRES_TARGETS="postgres10 postgres11" PYTHON_SINGLE_TARGET="python3_8" PYTHON_TARGETS="python3_8" QEMU_SOFTMMU_TARGETS="arm aarch64 i386 x86_64 riscv32 riscv64" QEMU_USER_TARGETS="arm aarch64" RUBY_TARGETS="ruby27" USERLAND="GNU" VIDEO_CARDS="intel i965 iris" XTABLES_ADDONS="quota2 psd pknock lscan length2 ipv4options ipset ipp2p iface geoip fuzzy condition tee tarpit sysrq steal rawnat logmark ipmark dhcpmac delude chaos account"
Unset:  CPPFLAGS, CTARGET, EMERGE_DEFAULT_OPTS, LINGUAS, PORTAGE_BINHOST, PORTAGE_BUNZIP2_COMMAND, PORTAGE_COMPRESS, PORTAGE_COMPRESS_FLAGS, PORTAGE_RSYNC_EXTRA_OPTS
Comment 1 Joshua Kinard gentoo-dev 2020-07-19 20:30:59 UTC
Ran into a similar issue where ALLOW_RULE(statx) was needed as well as for writev.  Discovered on MIPS big-endian chroot again sys-libs/musl-1.2.0-r1.

Will attach a patch for file-5.39-r2 that can go into the musl overlay to resolve this until changes are sent upstream.
Comment 2 Joshua Kinard gentoo-dev 2020-07-19 20:33:07 UTC
Created attachment 649898 [details, diff]
Patch for file-5.39 to add ALLOW_RULE entries for 'statx' and 'writev'
Comment 3 Mike Gilbert gentoo-dev 2020-09-07 16:57:29 UTC
https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=728f8c43b8b540f37871be3080ac63c05a9cf6a7

commit 728f8c43b8b540f37871be3080ac63c05a9cf6a7
Author: Mike Gilbert <floppym@gentoo.org>
Date:   Mon Sep 7 12:55:11 2020 -0400

    sys-apps/file: backport a seccomp fix for musl
    
    Closes: https://bugs.gentoo.org/728978
    Signed-off-by: Mike Gilbert <floppym@gentoo.org>

 sys-apps/file/file-5.39-r1.ebuild                  | 140 ---------------------
 .../{file-5.39-r2.ebuild => file-5.39-r3.ebuild}   |   5 +-
 sys-apps/file/file-5.39.ebuild                     | 140 ---------------------
 .../file/files/file-5.39-add-missing-termios.patch |  35 +++---
 ...ndbox.patch => file-5.39-portage-sandbox.patch} |  18 ++-
 sys-apps/file/files/file-5.39-seccomp-musl.patch   |  37 ++++++
 .../file/files/file-5.39-seccomp_sandbox.patch     |  13 --
 7 files changed, 67 insertions(+), 321 deletions(-)