[Virtio-fs] [PATCH v2 2/2] virtiofsd: Add support of posix_acl

[Misono Tomohiro]

This commit adds support of posix_acl which is enabled by 'posix_acl'
option (default: disabled).

If posix_acl is enabled, virtiofsd handles umask handling otherwise done
in guest kenrel in order to treat default ACL correctly.

With this, ACL-related xfstest generic/{099,237,319,444} passes on XFS
backend.

Implementation:
  virtiofsd adds FUSE_CAP_POSIX_ACL/FUSE_CAP_DONT_MASK to INIT replay if
 posix_acl is enabled. This results in skipping umask handling in guest
 kernel. In turn, virtiofsd sets umask before creating files by using
 umask value included in fuse_request and restore umask after that.
 Note that calling umask() is ok since now each worker thread has called
 unshare(CLONE_FS) when starting up.

Signed-off-by: Misono Tomohiro <misono.tomohiro at jp.fujitsu.com>
---
 tools/virtiofsd/helper.c         |  3 +++
 tools/virtiofsd/passthrough_ll.c | 36 ++++++++++++++++++++++++++------
 tools/virtiofsd/seccomp.c        |  1 +
 3 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/tools/virtiofsd/helper.c b/tools/virtiofsd/helper.c
index 0801cf752c..97968a9385 100644
--- a/tools/virtiofsd/helper.c
+++ b/tools/virtiofsd/helper.c
@@ -171,6 +171,9 @@ void fuse_cmdline_help(void)
            "                               default: no_writeback\n"
            "    -o xattr|no_xattr          enable/disable xattr\n"
            "                               default: no_xattr\n"
+           "    -o posix_acl|no_posxi_acl  enable/disable posix_acl\n"
+           "                               enabling this also enables xattr\n"
+           "                               default: no_posix_acl\n"
            );
 }
 
diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index 6bcc33e0eb..e1bb261b51 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -152,6 +152,7 @@ struct lo_data {
     int flock;
     int posix_lock;
     int xattr;
+    int posix_acl;
     char *source;
     double timeout;
     int cache;
@@ -182,6 +183,8 @@ static const struct fuse_opt lo_opts[] = {
     { "no_posix_lock", offsetof(struct lo_data, posix_lock), 0 },
     { "xattr", offsetof(struct lo_data, xattr), 1 },
     { "no_xattr", offsetof(struct lo_data, xattr), 0 },
+    { "posix_acl", offsetof(struct lo_data, posix_acl), 1 },
+    { "no_posix_acl", offsetof(struct lo_data, posix_acl), 0 },
     { "timeout=%lf", offsetof(struct lo_data, timeout), 0 },
     { "timeout=", offsetof(struct lo_data, timeout_set), 1 },
     { "cache=none", offsetof(struct lo_data, cache), CACHE_NONE },
@@ -587,6 +590,17 @@ static void lo_init(void *userdata, struct fuse_conn_info *conn)
         fuse_log(FUSE_LOG_DEBUG, "lo_init: disabling readdirplus\n");
         conn->want &= ~FUSE_CAP_READDIRPLUS;
     }
+
+    if (conn->capable & FUSE_CAP_POSIX_ACL) {
+        if (lo->posix_acl) {
+            if (!lo->xattr)  {
+                fuse_log(FUSE_LOG_DEBUG, "lo_init: enabling xattr for ACL\n");
+                lo->xattr = 1;
+            }
+            fuse_log(FUSE_LOG_DEBUG, "lo_init: enabling ACL\n");
+            conn->want |= (FUSE_CAP_POSIX_ACL | FUSE_CAP_DONT_MASK);
+        }
+    }
 }
 
 static int64_t *version_ptr(struct lo_data *lo, struct lo_inode *inode)
@@ -1137,9 +1151,11 @@ static void lo_lookup(fuse_req_t req, fuse_ino_t parent, const char *name)
 /*
  * Change to uid/gid of caller so that file is created with
  * ownership of caller.
+ * Also update umask if posix_acl is enabled.
  * TODO: What about selinux context?
  */
-static int lo_change_cred(fuse_req_t req, struct lo_cred *old)
+static int lo_change_cred_and_umask(fuse_req_t req, struct lo_cred *old,
+                                    struct lo_data *lo)
 {
     int res;
 
@@ -1159,11 +1175,15 @@ static int lo_change_cred(fuse_req_t req, struct lo_cred *old)
         return errno_save;
     }
 
+    if (lo->posix_acl) {
+        umask(req->ctx.umask);
+    }
+
     return 0;
 }
 
 /* Regain Privileges */
-static void lo_restore_cred(struct lo_cred *old)
+static void lo_restore_cred_and_umask(struct lo_cred *old, struct lo_data *lo)
 {
     int res;
 
@@ -1178,6 +1198,10 @@ static void lo_restore_cred(struct lo_cred *old)
         fuse_log(FUSE_LOG_ERR, "setegid(%u): %m\n", old->egid);
         exit(1);
     }
+
+    if (lo->posix_acl) {
+        umask(0);
+    }
 }
 
 static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,
@@ -1204,7 +1228,7 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,
 
     saverr = ENOMEM;
 
-    saverr = lo_change_cred(req, &old);
+    saverr = lo_change_cred_and_umask(req, &old, lo);
     if (saverr) {
         goto out;
     }
@@ -1213,7 +1237,7 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,
 
     saverr = errno;
 
-    lo_restore_cred(&old);
+    lo_restore_cred_and_umask(&old, lo);
 
     if (res == -1) {
         goto out;
@@ -1898,7 +1922,7 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
         return;
     }
 
-    err = lo_change_cred(req, &old);
+    err = lo_change_cred_and_umask(req, &old, lo);
     if (err) {
         goto out;
     }
@@ -1908,7 +1932,7 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
     fd = openat(parent_inode->fd, name, (fi->flags | O_CREAT) & ~O_NOFOLLOW,
                 mode);
     err = fd == -1 ? errno : 0;
-    lo_restore_cred(&old);
+    lo_restore_cred_and_umask(&old, lo);
 
     if (!err) {
         ssize_t fh;
diff --git a/tools/virtiofsd/seccomp.c b/tools/virtiofsd/seccomp.c
index 9ee99e4725..1b6f579452 100644
--- a/tools/virtiofsd/seccomp.c
+++ b/tools/virtiofsd/seccomp.c
@@ -102,6 +102,7 @@ static const int syscall_whitelist[] = {
     SCMP_SYS(symlinkat),
     SCMP_SYS(time), /* Rarely needed, except on static builds */
     SCMP_SYS(tgkill),
+    SCMP_SYS(umask),
     SCMP_SYS(unlinkat),
     SCMP_SYS(unshare),
     SCMP_SYS(utimensat),
-- 
2.21.1