Filesystem: Read-only file system checks

 o Make sure EROFS is indicated for write operations on a read-only file
   system.
 o Add error indication for read-only file systems in fchmod() and
   fchown() according to POSIX.

3 files changed, 40 insertions, 26 deletions

diff --git a/cpukit/libcsupport/src/fchmod.c b/cpukit/libcsupport/src/fchmod.c
index e651066a77..14fb416f68 100644
--- a/cpukit/libcsupport/src/fchmod.c
+++ b/cpukit/libcsupport/src/fchmod.c
@@ -28,9 +28,14 @@ int fchmod( int fd, mode_t mode )
   iop = rtems_libio_iop( fd );
   rtems_libio_check_is_open(iop);
 
-  rtems_filesystem_instance_lock( &iop->pathinfo );
-  rv = (*iop->pathinfo.ops->fchmod_h)( &iop->pathinfo, mode );
-  rtems_filesystem_instance_unlock( &iop->pathinfo );
+  if (iop->pathinfo.mt_entry->writeable) {
+    rtems_filesystem_instance_lock( &iop->pathinfo );
+    rv = (*iop->pathinfo.ops->fchmod_h)( &iop->pathinfo, mode );
+    rtems_filesystem_instance_unlock( &iop->pathinfo );
+  } else {
+    errno = EROFS;
+    rv = -1;
+  }
 
   return rv;
 }
diff --git a/cpukit/libcsupport/src/fchown.c b/cpukit/libcsupport/src/fchown.c
index b5891bf36d..d0d04005d8 100644
--- a/cpukit/libcsupport/src/fchown.c
+++ b/cpukit/libcsupport/src/fchown.c
@@ -28,11 +28,14 @@ int fchown( int fd, uid_t owner, gid_t group )
   iop = rtems_libio_iop( fd );
   rtems_libio_check_is_open(iop);
 
-  rtems_libio_check_permissions( iop, LIBIO_FLAGS_WRITE );
-
-  rtems_filesystem_instance_lock( &iop->pathinfo );
-  rv = (*iop->pathinfo.ops->chown_h)( &iop->pathinfo, owner, group );
-  rtems_filesystem_instance_unlock( &iop->pathinfo );
+  if (iop->pathinfo.mt_entry->writeable) {
+    rtems_filesystem_instance_lock( &iop->pathinfo );
+    rv = (*iop->pathinfo.ops->chown_h)( &iop->pathinfo, owner, group );
+    rtems_filesystem_instance_unlock( &iop->pathinfo );
+  } else {
+    errno = EROFS;
+    rv = -1;
+  }
 
   return rv;
 }
diff --git a/cpukit/libcsupport/src/sup_fs_eval_path.c b/cpukit/libcsupport/src/sup_fs_eval_path.c
index 1940cce745..c827ba72f8 100644
--- a/cpukit/libcsupport/src/sup_fs_eval_path.c
+++ b/cpukit/libcsupport/src/sup_fs_eval_path.c
@@ -68,26 +68,32 @@ static void check_access(
 )
 {
   const rtems_filesystem_location_info_t *currentloc = &ctx->currentloc;
-  struct stat st;
-  int rv;
-
-  st.st_mode = 0;
-  st.st_uid = 0;
-  st.st_gid = 0;
-  rv = (*currentloc->handlers->fstat_h)(currentloc, &st);
-  if (rv == 0) {
-    bool access_ok = rtems_filesystem_check_access(
-      eval_flags,
-      st.st_mode,
-      st.st_uid,
-      st.st_gid
-    );
-
-    if (!access_ok) {
-      rtems_filesystem_eval_path_error(ctx, EACCES);
+  const rtems_filesystem_mount_table_entry_t *mt_entry = currentloc->mt_entry;
+
+  if ((eval_flags & RTEMS_LIBIO_PERMS_WRITE) == 0 || mt_entry->writeable) {
+    struct stat st;
+    int rv;
+
+    st.st_mode = 0;
+    st.st_uid = 0;
+    st.st_gid = 0;
+    rv = (*currentloc->handlers->fstat_h)(currentloc, &st);
+    if (rv == 0) {
+      bool access_ok = rtems_filesystem_check_access(
+        eval_flags,
+        st.st_mode,
+        st.st_uid,
+        st.st_gid
+      );
+
+      if (!access_ok) {
+        rtems_filesystem_eval_path_error(ctx, EACCES);
+      }
+    } else {
+      rtems_filesystem_eval_path_error(ctx, 0);
     }
   } else {
-    rtems_filesystem_eval_path_error(ctx, 0);
+    rtems_filesystem_eval_path_error(ctx, EROFS);
   }
 }