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-rw-r--r--glnx-fdio.c42
-rw-r--r--glnx-fdio.h4
2 files changed, 44 insertions, 2 deletions
diff --git a/glnx-fdio.c b/glnx-fdio.c
index 1dc5ffd..12879cd 100644
--- a/glnx-fdio.c
+++ b/glnx-fdio.c
@@ -363,8 +363,7 @@ glnx_link_tmpfile_at (GLnxTmpfile *tmpf,
{
/* This case we have O_TMPFILE, so our reference to it is via /proc/self/fd */
char proc_fd_path[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(tmpf->fd) + 1];
-
- sprintf (proc_fd_path, "/proc/self/fd/%i", tmpf->fd);
+ snprintf (proc_fd_path, sizeof (proc_fd_path), "/proc/self/fd/%i", tmpf->fd);
if (replace)
{
@@ -424,6 +423,45 @@ glnx_link_tmpfile_at (GLnxTmpfile *tmpf,
return TRUE;
}
+/* glnx_tmpfile_reopen_rdonly:
+ * @tmpf: tmpfile
+ * @error: Error
+ *
+ * Give up write access to the file descriptior. One use
+ * case for this is fs-verity, which requires a read-only fd.
+ * It could also be useful to allocate an anonymous tmpfile
+ * write some sort of caching/indexing data to it, then reopen it
+ * read-only thereafter.
+ **/
+gboolean
+glnx_tmpfile_reopen_rdonly (GLnxTmpfile *tmpf,
+ GError **error)
+{
+ g_return_val_if_fail (tmpf->fd >= 0, FALSE);
+ g_return_val_if_fail (tmpf->src_dfd == AT_FDCWD || tmpf->src_dfd >= 0, FALSE);
+
+ glnx_fd_close int rdonly_fd = -1;
+
+ if (tmpf->path)
+ {
+ if (!glnx_openat_rdonly (tmpf->src_dfd, tmpf->path, FALSE, &rdonly_fd, error))
+ return FALSE;
+ }
+ else
+ {
+ /* This case we have O_TMPFILE, so our reference to it is via /proc/self/fd */
+ char proc_fd_path[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(tmpf->fd) + 1];
+ snprintf (proc_fd_path, sizeof (proc_fd_path), "/proc/self/fd/%i", tmpf->fd);
+
+ if (!glnx_openat_rdonly (AT_FDCWD, proc_fd_path, TRUE, &rdonly_fd, error))
+ return FALSE;
+ }
+
+ glnx_close_fd (&tmpf->fd);
+ tmpf->fd = glnx_steal_fd (&rdonly_fd);
+ return TRUE;
+}
+
/**
* glnx_openat_rdonly:
* @dfd: File descriptor for origin directory
diff --git a/glnx-fdio.h b/glnx-fdio.h
index d97ea36..9c57dc5 100644
--- a/glnx-fdio.h
+++ b/glnx-fdio.h
@@ -111,6 +111,10 @@ glnx_link_tmpfile_at (GLnxTmpfile *tmpf,
GError **error);
gboolean
+glnx_tmpfile_reopen_rdonly (GLnxTmpfile *tmpf,
+ GError **error);
+
+gboolean
glnx_openat_rdonly (int dfd,
const char *path,
gboolean follow,