srcversion hash does not cover all the module's source/dependency files

From: Radek Krejci
Date: Wed Feb 14 2024 - 04:43:49 EST


Hi,
I've found a bug in modpost - when it gets the list of source files to generate srcversion hash, it skips all the source/dependency files except for the first one.

There is patch [1] in v5.8rc1 replacing get_next_line() by get_line() in parse_source_file() function. Besides other things, the difference between those 2 functions is that get_next_line() trims the leading spaces of the line being returned. The issue is, that the source (deps_ located at the same directory) file names in the list, being processed in parse_source_file(), are indented. So, when the code gets to "Terminate line at first space, to get rid of final ' \'", it effectively hides the source file name from further processing, since the first space is at the beginning of the line.

I checked this behavior with modpost from v5.4 and v5.14 (and confirmed with the current master in git). In my case, my kernel module had just 2 source files - mymodule.c and mymodule.h (both located at the same directory). With modpost from v5.4, the code change in any of the files was reflected in srcversion hash. But with modpost from v5.14 (and master) there is no hash change when the code change appears in the header file, which is listed at the end of the deps_ list. I believe this is quite simple to reproduce with any module, but if needed, I can prepare some example code to reproduce the issue.

I noticed this [2] email thread in the list. It mentions a similar issue. However, since it happened a half year before the change [1] was introduced and because I was unable to find any further details, including the promised patch, I believe that these 2 things are unrelated.

The enclosed patch worked for me, but there might be some other consequences that I've missed, so feel free to modify it on your own or let me know.

Is there anything else I can do to help fixing this issue?

Regards,
Radek Krejci


[1] - https://lore.kernel.org/linux-kbuild/20200601055731.3006266-26-masahiroy@xxxxxxxxxx/
[2] - https://lore.kernel.org/linux-kbuild/CAN19L9G-mFN-MTmw0FS3ZX4d1MjeoL2U+s-Fk7Qw9UYWn5Q1YA@xxxxxxxxxxxxxx/ From 8e14b8fdb71385ab53af48fc56d9cd9e323e1265 Mon Sep 17 00:00:00 2001
From: Radek Krejci <radek.krejci@xxxxxxxxxx>
Date: Wed, 14 Feb 2024 10:14:07 +0100
Subject: [PATCH] modpost: trim leading spaces when processing source files
list

get_line() does not trim the leading spaces, but the
parse_source_files() expects to get lines with source files paths where
the first space occurs after the file path.

Signed-off-by: Radek Krejci <radek.krejci@xxxxxxxxxx>
---
scripts/mod/sumversion.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/scripts/mod/sumversion.c b/scripts/mod/sumversion.c
index 31066bfdba04..dc4878502276 100644
--- a/scripts/mod/sumversion.c
+++ b/scripts/mod/sumversion.c
@@ -326,7 +326,12 @@ static int parse_source_files(const char *objfile, struct md4_ctx *md)

/* Sum all files in the same dir or subdirs. */
while ((line = get_line(&pos))) {
- char* p = line;
+ char* p;
+
+ /* trim the leading spaces away */
+ while (isspace(*line))
+ line++;
+ p = line;

if (strncmp(line, "source_", sizeof("source_")-1) == 0) {
p = strrchr(line, ' ');
--
2.43.0