From: Stefan Hajnoczi <stefanha@redhat.com>

Date: Mon, 27 Jan 2020 19:01:36 +0000

Subject: [PATCH] virtiofsd: add --syslog command-line option

MIME-Version: 1.0

Content-Type: text/plain; charset=UTF-8

Content-Transfer-Encoding: 8bit

Sometimes collecting output from stderr is inconvenient or does not fit

within the overall logging architecture.  Add syslog(3) support for

cases where stderr cannot be used.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

dgilbert: Reworked as a logging function

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

(cherry picked from commit f185621d41f03a23b55795b89e6584253fa23505)

---

 tools/virtiofsd/fuse_lowlevel.h  |  1 +

 tools/virtiofsd/helper.c         |  2 ++

 tools/virtiofsd/passthrough_ll.c | 50 ++++++++++++++++++++++++++++++--

 tools/virtiofsd/seccomp.c        | 32 ++++++++++++++------

 tools/virtiofsd/seccomp.h        |  4 ++-

 5 files changed, 76 insertions(+), 13 deletions(-)

diff --git a/tools/virtiofsd/fuse_lowlevel.h b/tools/virtiofsd/fuse_lowlevel.h

index 0d61df8110..f2750bc189 100644

--- a/tools/virtiofsd/fuse_lowlevel.h

+++ b/tools/virtiofsd/fuse_lowlevel.h

@@ -1795,6 +1795,7 @@ struct fuse_cmdline_opts {

     int show_version;

     int show_help;

     int print_capabilities;

+    int syslog;

     unsigned int max_idle_threads;

 };

diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c

index 5531425223..9692ef9f1f 100644

--- a/tools/virtiofsd/helper.c

+++ b/tools/virtiofsd/helper.c

@@ -54,6 +54,7 @@ static const struct fuse_opt fuse_helper_opts[] = {

     FUSE_HELPER_OPT("subtype=", nodefault_subtype),

     FUSE_OPT_KEY("subtype=", FUSE_OPT_KEY_KEEP),

     FUSE_HELPER_OPT("max_idle_threads=%u", max_idle_threads),

+    FUSE_HELPER_OPT("--syslog", syslog),

     FUSE_OPT_END

 };

@@ -138,6 +139,7 @@ void fuse_cmdline_help(void)

            "    -V   --version             print version\n"

            "    --print-capabilities       print vhost-user.json\n"

            "    -d   -o debug              enable debug output (implies -f)\n"

+           "    --syslog                   log to syslog (default stderr)\n"

            "    -f                         foreground operation\n"

            "    --daemonize                run in background\n"

            "    -o max_idle_threads        the maximum number of idle worker "

diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c

index c281d817af..0372aca143 100644

--- a/tools/virtiofsd/passthrough_ll.c

+++ b/tools/virtiofsd/passthrough_ll.c

@@ -58,6 +58,7 @@

 #include <sys/types.h>

 #include <sys/wait.h>

 #include <sys/xattr.h>

+#include <syslog.h>

 #include <unistd.h>

 #include "passthrough_helpers.h"

@@ -138,6 +139,7 @@ static const struct fuse_opt lo_opts[] = {

     { "norace", offsetof(struct lo_data, norace), 1 },

     FUSE_OPT_END

 };

+static bool use_syslog = false;

 static void unref_inode(struct lo_data *lo, struct lo_inode *inode, uint64_t n);

@@ -2262,11 +2264,12 @@ static void setup_mounts(const char *source)

  * Lock down this process to prevent access to other processes or files outside

  * source directory.  This reduces the impact of arbitrary code execution bugs.

  */

-static void setup_sandbox(struct lo_data *lo, struct fuse_session *se)

+static void setup_sandbox(struct lo_data *lo, struct fuse_session *se,

+                          bool enable_syslog)

 {

     setup_namespaces(lo, se);

     setup_mounts(lo->source);

-    setup_seccomp();

+    setup_seccomp(enable_syslog);

 }

 /* Raise the maximum number of open file descriptors */

@@ -2298,6 +2301,42 @@ static void setup_nofile_rlimit(void)

     }

 }

+static void log_func(enum fuse_log_level level, const char *fmt, va_list ap)

+{

+    if (use_syslog) {

+        int priority = LOG_ERR;

+        switch (level) {

+        case FUSE_LOG_EMERG:

+            priority = LOG_EMERG;

+            break;

+        case FUSE_LOG_ALERT:

+            priority = LOG_ALERT;

+            break;

+        case FUSE_LOG_CRIT:

+            priority = LOG_CRIT;

+            break;

+        case FUSE_LOG_ERR:

+            priority = LOG_ERR;

+            break;

+        case FUSE_LOG_WARNING:

+            priority = LOG_WARNING;

+            break;

+        case FUSE_LOG_NOTICE:

+            priority = LOG_NOTICE;

+            break;

+        case FUSE_LOG_INFO:

+            priority = LOG_INFO;

+            break;

+        case FUSE_LOG_DEBUG:

+            priority = LOG_DEBUG;

+            break;

+        }

+        vsyslog(priority, fmt, ap);

+    } else {

+        vfprintf(stderr, fmt, ap);

+    }

+}

+

 int main(int argc, char *argv[])

 {

     struct fuse_args args = FUSE_ARGS_INIT(argc, argv);

@@ -2336,6 +2375,11 @@ int main(int argc, char *argv[])

     if (fuse_parse_cmdline(&args, &opts) != 0) {

         return 1;

     }

+    fuse_set_log_func(log_func);

+    use_syslog = opts.syslog;

+    if (use_syslog) {

+        openlog("virtiofsd", LOG_PID, LOG_DAEMON);

+    }

     if (opts.show_help) {

         printf("usage: %s [options]\n\n", argv[0]);

         fuse_cmdline_help();

@@ -2424,7 +2468,7 @@ int main(int argc, char *argv[])

     /* Must be before sandbox since it wants /proc */

     setup_capng();

-    setup_sandbox(&lo, se);

+    setup_sandbox(&lo, se, opts.syslog);

     /* Block until ctrl+c or fusermount -u */

     ret = virtio_loop(se);

diff --git a/tools/virtiofsd/seccomp.c b/tools/virtiofsd/seccomp.c

index 691fb63dea..2d9d4a7ec0 100644

--- a/tools/virtiofsd/seccomp.c

+++ b/tools/virtiofsd/seccomp.c

@@ -107,11 +107,28 @@ static const int syscall_whitelist[] = {

     SCMP_SYS(writev),

 };

-void setup_seccomp(void)

+/* Syscalls used when --syslog is enabled */

+static const int syscall_whitelist_syslog[] = {

+    SCMP_SYS(sendto),

+};

+

+static void add_whitelist(scmp_filter_ctx ctx, const int syscalls[], size_t len)

 {

-    scmp_filter_ctx ctx;

     size_t i;

+    for (i = 0; i < len; i++) {

+        if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW, syscalls[i], 0) != 0) {

+            fuse_log(FUSE_LOG_ERR, "seccomp_rule_add syscall %d failed\n",

+                     syscalls[i]);

+            exit(1);

+        }

+    }

+}

+

+void setup_seccomp(bool enable_syslog)

+{

+    scmp_filter_ctx ctx;

+

 #ifdef SCMP_ACT_KILL_PROCESS

     ctx = seccomp_init(SCMP_ACT_KILL_PROCESS);

     /* Handle a newer libseccomp but an older kernel */

@@ -126,13 +143,10 @@ void setup_seccomp(void)

         exit(1);

     }

-    for (i = 0; i < G_N_ELEMENTS(syscall_whitelist); i++) {

-        if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW,

-                             syscall_whitelist[i], 0) != 0) {

-            fuse_log(FUSE_LOG_ERR, "seccomp_rule_add syscall %d",

-                     syscall_whitelist[i]);

-            exit(1);

-        }

+    add_whitelist(ctx, syscall_whitelist, G_N_ELEMENTS(syscall_whitelist));

+    if (enable_syslog) {

+        add_whitelist(ctx, syscall_whitelist_syslog,

+                      G_N_ELEMENTS(syscall_whitelist_syslog));

     }

     /* libvhost-user calls this for post-copy migration, we don't need it */

diff --git a/tools/virtiofsd/seccomp.h b/tools/virtiofsd/seccomp.h

index 86bce72652..d47c8eade6 100644

--- a/tools/virtiofsd/seccomp.h

+++ b/tools/virtiofsd/seccomp.h

@@ -9,6 +9,8 @@

 #ifndef VIRTIOFSD_SECCOMP_H

 #define VIRTIOFSD_SECCOMP_H

-void setup_seccomp(void);

+#include <stdbool.h>

+

+void setup_seccomp(bool enable_syslog);

 #endif /* VIRTIOFSD_SECCOMP_H */