[PATCH 06/29] modpost: avoid false-positive file open error

Masahiro Yamada
2020-05-17T09:49:34Z

One problem of grab_file() is that it cannot distinguish the following
two cases:

- I cannot read the file (the file does not exist, or read permission
is not set)

- It can read the file, but the file size is zero

This is because grab_file() calls mmap(), which requires the mapped
length is greater than 0. Hence, grab_file() fails for both cases.

If an empty header file were included from a module that requires checksum
calculation, the following warning would be printed:

WARNING: modpost: could not open ...: Invalid argument

An empty file is a valid source file, so it should not fail.

Use read_text_file() instead. It can read a zero-length file.
Then, parse_file() will succeed with doing nothing.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

scripts/mod/sumversion.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/scripts/mod/sumversion.c b/scripts/mod/sumversion.c
index f9df0b1863f1..a1c7b0f4cd5a 100644
--- a/scripts/mod/sumversion.c
+++ b/scripts/mod/sumversion.c
@@ -258,10 +258,12 @@ static int parse_file(const char *fname, struct md4_ctx *md)
char *file;
unsigned long i, len;

- file = grab_file(fname, &len);
+ file = read_text_file(fname);
if (!file)
return 0;

+ len = strlen(file);
+
for (i = 0; i < len; i++) {
/* Collapse and ignore \ and CR. */
if (file[i] == '\\' && (i+1 < len) && file[i+1] == '\n') {
@@ -287,7 +289,7 @@ static int parse_file(const char *fname, struct md4_ctx *md)

add_char(file[i], md);
}
- release_file(file, len);
+ free(file);
return 1;
}
/* Check whether the file is a static library or not */
--
2.25.1