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master 27af0a3: Seccomp filter: deal with arch_prctl(ARCH_CET_STATUS, ..
From: |
Philipp Stephani |
Subject: |
master 27af0a3: Seccomp filter: deal with arch_prctl(ARCH_CET_STATUS, ...). |
Date: |
Mon, 19 Apr 2021 15:31:31 -0400 (EDT) |
branch: master
commit 27af0a3dc8b6b45879904bbc5d54b0677f84a5ff
Author: Philipp Stephani <phst@google.com>
Commit: Philipp Stephani <phst@google.com>
Seccomp filter: deal with arch_prctl(ARCH_CET_STATUS, ...).
The dynamic loader of GNU libc 2.28 uses this system call to
initialize CPU information, see
https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/x86/cpu-features.c;hb=glibc-2.28#l28.
Simulating an older kernel by returning EINVAL should be the most
harmless rule here.
The ARCH_CET_STATUS symbol isn't yet exposed by the kernel headers;
see the FIXME at the top of
https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/x86/include/asm/prctl.h;hb=glibc-2.28.
* lib-src/seccomp-filter.c (ARCH_CET_STATUS): Define if not
already present. Inline the value because there doesn't seem to
be a header file exporting this constant yet.
(main): Make ARCH_CET_STATUS subfunction of arch_prctl return EINVAL.
---
lib-src/seccomp-filter.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/lib-src/seccomp-filter.c b/lib-src/seccomp-filter.c
index 8f8a990..31d0809 100644
--- a/lib-src/seccomp-filter.c
+++ b/lib-src/seccomp-filter.c
@@ -60,6 +60,10 @@ variants of those files that can be used to sandbox Emacs
before
#include "verify.h"
+#ifndef ARCH_CET_STATUS
+#define ARCH_CET_STATUS 0x3001
+#endif
+
static ATTRIBUTE_FORMAT_PRINTF (2, 3) _Noreturn void
fail (int error, const char *format, ...)
{
@@ -345,6 +349,8 @@ main (int argc, char **argv)
RULE (SCMP_ACT_ALLOW, SCMP_SYS (set_tid_address));
RULE (SCMP_ACT_ALLOW, SCMP_SYS (arch_prctl),
SCMP_A0_32 (SCMP_CMP_EQ, ARCH_SET_FS));
+ RULE (SCMP_ACT_ERRNO (EINVAL), SCMP_SYS (arch_prctl),
+ SCMP_A0_32 (SCMP_CMP_EQ, ARCH_CET_STATUS));
RULE (SCMP_ACT_ALLOW, SCMP_SYS (statfs));
/* We want to allow starting the Emacs binary itself with the
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Philipp Stephani <=