From f531c1b5de65bc687bdcca69e7649fe2db5b6d87 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Mon, 1 Jun 2020 14:57:18 +0900 Subject: [PATCH] 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 4be40e22233c ("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 91341d4b2c19 ("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 b7dca6dd1e59 ("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 --- scripts/mod/sumversion.c | 28 +++++++++++----------------- 1 file changed, 11 insertions(+), 17 deletions(-) diff --git a/scripts/mod/sumversion.c b/scripts/mod/sumversion.c index f27f224..5fb142d 100644 --- a/scripts/mod/sumversion.c +++ b/scripts/mod/sumversion.c @@ -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); } -- 2.7.4