worker-privs: allow munmap/mremap/madvise for isolated workers

Fix worker crashes on musl-based systems when isolate-workers = true by allowing munmap, mremap, and madvise in the worker seccomp filter.

Move seccomp coverage to Alpine CI and use oc_syslog for seccomp trap diagnostics instead of direct write()-based output.

Keep glibc backtrace diagnostics as the default and allow musl builds to select the syscall-only fallback with the assume-glibc Meson option.

Resolves: #749
Signed-off-by: Alex Protsko <fidget2015@yahoo.com>

.gitlab-ci.yml

@@ -221,7 +221,7 @@ musl/Alpine:
   stage: testing
   image: $CI_REGISTRY/$BUILD_IMAGES_PROJECT:$ALPINE_BUILD
   script:
-  - meson setup build -Dwith-werror=true
+  - meson setup build -Dwith-werror=true -Dassume-glibc=false
   - ninja -C build -j$JOBS
   tags:
   - saas-linux-small-amd64
@@ -339,6 +339,32 @@ seccomp/Fedora:
     untracked: true
     when: on_failure
 
+# Tests seccomp filters under musl/Alpine to catch allocator/syscall gaps
+seccomp/Alpine:
+  stage: testing
+  image: $CI_REGISTRY/$BUILD_IMAGES_PROJECT:$ALPINE_BUILD
+  script:
+  - apk add --no-cache bash
+  - chmod -R o-w tests/data/raddb
+  - git submodule update --init
+  - meson setup build -Dseccomp-trap=true -Dassume-glibc=false
+  - ninja -C build -j$JOBS
+  - >-
+    meson test -C build --no-rebuild --num-processes 1 --print-errorlogs
+    session-timeout traffic bandwidth
+    oc-aes256-gcm-cipher oc-aes128-gcm-cipher
+    ac-aes128-gcm-cipher ac-aes256-gcm-cipher
+    no-dtls-cipher
+  tags:
+  - saas-linux-medium-amd64
+  except:
+  - tags
+  - schedules
+  artifacts:
+    expire_in: 1 week
+    untracked: true
+    when: on_failure
+
 # Tests per-worker RLIMIT_DATA by making setrlimit failures fatal
 worker-memory-limit/Fedora:
   stage: testing

meson.build

@@ -362,6 +362,7 @@ cdata.set('PROC_FS_SUPPORTED',                proc_fs)
 cdata.set('SUPPORT_OIDC_AUTH',                oidc_enabled)
 cdata.set('TRY_SHA2_CRYPT',                   try_sha2_crypt)
 cdata.set('USE_SECCOMP_TRAP',                 get_option('seccomp-trap'))
+cdata.set('ASSUME_GLIBC',                     get_option('assume-glibc'))
 cdata.set('WORKER_MEMORY_LIMIT_TEST',         get_option('worker-memory-limit-test'))
 
 # These three are used in #elif (not #ifdef), so they must be 1 or undef (not empty)

meson_options.txt

@@ -21,6 +21,7 @@ option('local-llhttp',      type: 'boolean',  value: true,      description: 'Us
 option('local-protobuf',    type: 'boolean',  value: false,     description: 'Force use of bundled protobuf-c')
 option('local-pcl',         type: 'boolean',  value: true,      description: 'Use bundled PCL (default); false to require system pcl')
 option('seccomp-trap',      type: 'boolean',  value: false,     description: 'Filtered syscalls fail with a signal (for CI/testing)')
+option('assume-glibc',      type: 'boolean',  value: true,      description: 'Use glibc backtrace support for seccomp trap diagnostics')
 option('worker-memory-limit-test', type: 'boolean', value: false, description: 'RLIMIT_DATA failures in worker are fatal (for CI/testing)')
 option('root-tests',        type: 'boolean',  value: true,      description: 'Enable tests requiring root/namespaces')
 option('serial-heavy-tests', type: 'boolean', value: false,     description: 'Run iperf3-heavy tests serially to avoid ASAN memory exhaustion under parallel load')

src/worker-privs.c

@@ -40,14 +40,24 @@
 
 #ifdef USE_SECCOMP_TRAP
 #define _SECCOMP_ERR SCMP_ACT_TRAP
+#ifdef ASSUME_GLIBC
 #include <execinfo.h>
-#include <signal.h>
+#endif /* ASSUME_GLIBC */
+
 void sigsys_action(int sig, siginfo_t *info, void *ucontext)
 {
+	(void)sig;
+	(void)ucontext;
+
+#ifdef ASSUME_GLIBC
 	char *call_addr = *backtrace_symbols(&info->si_call_addr, 1);
 
 	oc_syslog(LOG_ERR, "Function %s called disabled syscall %d", call_addr,
 		  info->si_syscall);
+#else
+	oc_syslog(LOG_ERR, "seccomp trap: syscall %d at %p", info->si_syscall,
+		  info->si_call_addr);
+#endif /* ASSUME_GLIBC */
 	exit(EXIT_FAILURE);
 }
 
@@ -135,9 +145,12 @@ int disable_system_calls(struct worker_st *ws)
 	ADD_SYSCALL(setitimer, 0);
 	ADD_SYSCALL(getpid, 0);
 
-	/* memory allocation - both are used by different platforms */
+	/* memory allocations used by different platforms */
 	ADD_SYSCALL(brk, 0);
 	ADD_SYSCALL(mmap, 0);
+	ADD_SYSCALL(munmap, 0);
+	ADD_SYSCALL(mremap, 0);
+	ADD_SYSCALL(madvise, 0);
 
 #if defined(SYS_getrandom) || defined(__NR_getrandom)
 	ADD_SYSCALL(getrandom, 0); /* used by gnutls 3.5.x */