[PATCH 4.19 42/74] kconfig: Clear "written" flag to avoid data loss

[Greg Kroah-Hartman]

From: M. Vefa Bicakci <m.v.b@xxxxxxxxxx>

commit 0c5b6c28ed68becb692b43eae5e44d5aa7e160ce upstream.

Prior to this commit, starting nconfig, xconfig or gconfig, and saving
the .config file more than once caused data loss, where a .config file
that contained only comments would be written to disk starting from the
second save operation.

This bug manifests itself because the SYMBOL_WRITTEN flag is never
cleared after the first call to conf_write, and subsequent calls to
conf_write then skip all of the configuration symbols due to the
SYMBOL_WRITTEN flag being set.

This commit resolves this issue by clearing the SYMBOL_WRITTEN flag
from all symbols before conf_write returns.

Fixes: 8e2442a5f86e ("kconfig: fix missing choice values in auto.conf")
Cc: linux-stable <stable@xxxxxxxxxxxxxxx> # 4.19+
Signed-off-by: M. Vefa Bicakci <m.v.b@xxxxxxxxxx>
Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 scripts/kconfig/confdata.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/scripts/kconfig/confdata.c
+++ b/scripts/kconfig/confdata.c
@@ -784,6 +784,7 @@ int conf_write(const char *name)
 	const char *str;
 	char dirname[PATH_MAX+1], tmpname[PATH_MAX+22], newname[PATH_MAX+8];
 	char *env;
+	int i;
 
 	dirname[0] = 0;
 	if (name && name[0]) {
@@ -860,6 +861,9 @@ next:
 	}
 	fclose(out);
 
+	for_all_symbols(i, sym)
+		sym->flags &= ~SYMBOL_WRITTEN;
+
 	if (*tmpname) {
 		strcat(dirname, basename);
 		strcat(dirname, ".old");