[PATCH 1/1] csv: detect end of csv file correctly

[Heinrich Schuchardt]

Shim produces random failures like

    sbat.c:46:parse_sbat_section() row->n_columns:0 SBAT_SECTION_COLUMNS:6
    Could not parse .sbat section data: Invalid Parameter

Adding debug statements shows output like

    csv.c:60:parse_csv_data() sbat[0x0]:
    sbat,1,SBAT Version,sbat,1,https://github.com/rhboot/shim/blob/main/SBAT.md
    shim,1,UEFI shim,shim,1,https://github.com/rhboot/shim

    csv.c:16:parse_csv_line() line:
    sbat,1,SBAT Version,sbat,1,https://github.com/rhboot/shim/blob/main/SBAT.md
    csv.c:35:parse_csv_line() n_columns 6
    csv.c:16:parse_csv_line() line:
    shim,1,UEFI shim,shim,1,https://github.com/rhboot/shim
    csv.c:35:parse_csv_line() n_columns 6
    csv.c:16:parse_csv_line() line:

    csv.c:35:parse_csv_line() n_columns 0
    csv.c:16:parse_csv_line() line:

    csv.c:35:parse_csv_line() n_columns 0
    csv.c:16:parse_csv_line() line:

In parse_csv_data() variable 'line' is a pointer with a value between
the values of 'data' and 'data_end'.

There is no reason to check that that it is non-zero after assigning it
from 'data' as we already check 'data'.

Instead after each line we must check that we have not reached the end of
the file marked by a '\0' character.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
---
 csv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/csv.c b/csv.c
index f6b37f1..b716632 100644
--- a/csv.c
+++ b/csv.c
@@ -63,10 +63,10 @@ parse_csv_data(char *data, char *data_end, size_t n_columns, list_t *list)
 
 	max = (uintptr_t)end - (uintptr_t)line + (end > line ? 1 : 0);
 
-	if (line && is_utf8_bom(line, max))
+	if (is_utf8_bom(line, max))
 		line += UTF8_BOM_SIZE;
 
-	while (line && line <= data_end) {
+	while (line <= data_end && *line) {
 		size_t entrysz = sizeof(char *) * n_columns + sizeof(struct csv_row);
 		struct csv_row *entry;
 		size_t m_columns = n_columns;
-- 
2.30.2