Merge remote-tracking branch 'remotes/dgilbert-gitlab/tags/pull-virtiofs-20220126' into staging

virtiofsd: Security fix

Fixes: CVE-2022-0358

# gpg: Signature made Wed 26 Jan 2022 10:46:44 GMT
# gpg:                using RSA key 45F5C71B4A0CB7FB977A9FA90516331EBC5BFDE7
# gpg: Good signature from "Dr. David Alan Gilbert (RH2) <dgilbert@redhat.com>" [full]
# Primary key fingerprint: 45F5 C71B 4A0C B7FB 977A  9FA9 0516 331E BC5B FDE7

* remotes/dgilbert-gitlab/tags/pull-virtiofs-20220126:
  virtiofsd: Drop membership of all supplementary groups (CVE-2022-0358)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

tools/virtiofsd/passthrough_ll.c

@@ -54,6 +54,7 @@
 #include <sys/wait.h>
 #include <sys/xattr.h>
 #include <syslog.h>
+#include <grp.h>
 
 #include "qemu/cutils.h"
 #include "passthrough_helpers.h"
@@ -1161,6 +1162,30 @@ static void lo_lookup(fuse_req_t req, fuse_ino_t parent, const char *name)
 #define OURSYS_setresuid SYS_setresuid
 #endif
 
+static void drop_supplementary_groups(void)
+{
+    int ret;
+
+    ret = getgroups(0, NULL);
+    if (ret == -1) {
+        fuse_log(FUSE_LOG_ERR, "getgroups() failed with error=%d:%s\n",
+                 errno, strerror(errno));
+        exit(1);
+    }
+
+    if (!ret) {
+        return;
+    }
+
+    /* Drop all supplementary groups. We should not need it */
+    ret = setgroups(0, NULL);
+    if (ret == -1) {
+        fuse_log(FUSE_LOG_ERR, "setgroups() failed with error=%d:%s\n",
+                 errno, strerror(errno));
+        exit(1);
+    }
+}
+
 /*
  * Change to uid/gid of caller so that file is created with
  * ownership of caller.
@@ -3926,6 +3951,8 @@ int main(int argc, char *argv[])
 
     qemu_init_exec_dir(argv[0]);
 
+    drop_supplementary_groups();
+
     pthread_mutex_init(&lo.mutex, NULL);
     lo.inodes = g_hash_table_new(lo_key_hash, lo_key_equal);
     lo.root.fd = -1;