strsep() modifies its first argument - buf.
If an error occurs in the parsing loop, an invalid pointer
will be passed to the free() function.
Make the pointer passed to free() match the return value of
read_text_file().

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 9413e7640564 ("kbuild: split the second line of *.mod into *.usyms")
Signed-off-by: Elena Salomatkina <esalomatkina@ispras.ru>
---
 scripts/mod/sumversion.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/scripts/mod/sumversion.c b/scripts/mod/sumversion.c
index 6bf9caca0968..03774957d8b9 100644
--- a/scripts/mod/sumversion.c
+++ b/scripts/mod/sumversion.c
@@ -385,7 +385,7 @@ static int parse_source_files(const char *objfile, struct md4_ctx *md)
 /* Calc and record src checksum. */
 void get_src_version(const char *modname, char sum[], unsigned sumlen)
 {
-	char *buf;
+	char *buf, *orig;
 	struct md4_ctx md;
 	char *fname;
 	char filelist[PATH_MAX + 1];
@@ -393,7 +393,7 @@ void get_src_version(const char *modname, char sum[], unsigned sumlen)
 	/* objects for a module are listed in the first line of *.mod file. */
 	snprintf(filelist, sizeof(filelist), "%s.mod", modname);
 
-	buf = read_text_file(filelist);
+	orig = buf = read_text_file(filelist);
 
 	md4_init(&md);
 	while ((fname = strsep(&buf, "\n"))) {
@@ -406,5 +406,5 @@ void get_src_version(const char *modname, char sum[], unsigned sumlen)
 
 	md4_final_ascii(&md, sum, sumlen);
 free:
-	free(buf);
+	free(orig);
 }
-- 
2.33.0

On Sun, Oct 13, 2024 at 10:11 PM Elena Salomatkina
<esalomatkina@ispras.ru> wrote:
>
> strsep() modifies its first argument - buf.
> If an error occurs in the parsing loop, an invalid pointer
> will be passed to the free() function.
> Make the pointer passed to free() match the return value of
> read_text_file().
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>
> Fixes: 9413e7640564 ("kbuild: split the second line of *.mod into *.usyms")
> Signed-off-by: Elena Salomatkina <esalomatkina@ispras.ru>


Thanks for spotting this.

This is a bike-shed, but please use 'p' or 'pos' as
the moving pointer and keep the 'buf'.

This is consistent with the following functions:

extract_crcs_for_object()
mod_set_crcs()
handle_white_list_exports()
read_dump()
parse_source_files()


> ---
>  scripts/mod/sumversion.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/scripts/mod/sumversion.c b/scripts/mod/sumversion.c
> index 6bf9caca0968..03774957d8b9 100644
> --- a/scripts/mod/sumversion.c
> +++ b/scripts/mod/sumversion.c
> @@ -385,7 +385,7 @@ static int parse_source_files(const char *objfile, struct md4_ctx *md)
>  /* Calc and record src checksum. */
>  void get_src_version(const char *modname, char sum[], unsigned sumlen)
>  {
> -       char *buf;
> +       char *buf, *orig;
>         struct md4_ctx md;
>         char *fname;
>         char filelist[PATH_MAX + 1];
> @@ -393,7 +393,7 @@ void get_src_version(const char *modname, char sum[], unsigned sumlen)
>         /* objects for a module are listed in the first line of *.mod file. */
>         snprintf(filelist, sizeof(filelist), "%s.mod", modname);
>
> -       buf = read_text_file(filelist);
> +       orig = buf = read_text_file(filelist);
>
>         md4_init(&md);
>         while ((fname = strsep(&buf, "\n"))) {
> @@ -406,5 +406,5 @@ void get_src_version(const char *modname, char sum[], unsigned sumlen)
>
>         md4_final_ascii(&md, sum, sumlen);
>  free:
> -       free(buf);
> +       free(orig);
>  }
> --
> 2.33.0
>
>


-- 
Best Regards
Masahiro Yamada