Commit f531c1b5 authored Jun 01, 2020 by Masahiro Yamada

modpost: fix potential mmap'ed file overrun in get_src_version()



I do not know how reliably this function works, but it looks dangerous
to me.

    strchr(sources, '\n');

... continues searching until it finds '\n' or it reaches the '\0'
terminator. In other words, 'sources' should be a null-terminated
string.

However, grab_file() just mmaps a file, so 'sources' is not terminated
with null byte. If the file does not contain '\n' at all, strchr() will
go beyond the mmap'ed memory.

Use read_text_file(), which loads the file content into a malloc'ed
buffer, appending null byte.

Here we are interested only in the first line of *.mod files. Use
get_line() helper to get the first line.

This also makes missing *.mod file a fatal error.

Commit 4be40e22 ("kbuild: do not emit src version warning for
non-modules") ignored missing *.mod files.

I do not fully understand what that commit addressed, but commit
91341d4b ("kbuild: introduce new option to enhance section mismatch
analysis") introduced partial section checks by using modpost. built-in.o
was parsed by modpost. Even modules had a problem because *.mod files
were created after the modpost check.

Commit b7dca6dd ("kbuild: create *.mod with full directory path and
remove MODVERDIR") stopped doing that. Now that modpost is only invoked
after the directory descend, *.mod files should always exist at the
modpost stage.

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

parent ac5100f5

scripts/mod/sumversion.c

+11 −17

Original line number	Diff line number	Diff line
		@@ -392,40 +392,34 @@ out:
		/* Calc and record src checksum. */
		void get_src_version(const char *modname, char sum[], unsigned sumlen)
		{
		void *file;
		unsigned long len;
		char buf, pos, *firstline;
		struct md4_ctx md;
		char sources, end, *fname;
		char *fname;
		char filelist[PATH_MAX + 1];

		/* objects for a module are listed in the first line of .mod file. /
		snprintf(filelist, sizeof(filelist), "%.*smod",
		(int)strlen(modname) - 1, modname);

		file = grab_file(filelist, &len);
		if (!file)
		/* not a module or .mod file missing - ignore */
		return;
		buf = read_text_file(filelist);

		sources = file;

		end = strchr(sources, '\n');
		if (!end) {
		pos = buf;
		firstline = get_line(&pos);
		if (!firstline) {
		warn("bad ending versions file for %s\n", modname);
		goto release;
		goto free;
		}
		*end = '\0';

		md4_init(&md);
		while ((fname = strsep(&sources, " ")) != NULL) {
		while ((fname = strsep(&firstline, " "))) {
		if (!*fname)
		continue;
		if (!(is_static_library(fname)) &&
		!parse_source_files(fname, &md))
		goto release;
		goto free;
		}

		md4_final_ascii(&md, sum, sumlen);
		release:
		release_file(file, len);
		free:
		free(buf);
		}

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