From 19e525ebbb88016721aeb4019d6bc0972513e3b5 Mon Sep 17 00:00:00 2001 From: Max Kellermann Date: Thu, 15 Feb 2024 15:13:21 +0100 Subject: [PATCH] modpost: fix null pointer dereference [ Upstream commit 23dfd914d2bfc4c9938b0084dffd7105de231d98 ] If the find_fromsym() call fails and returns NULL, the warn() call will dereference this NULL pointer and cause the program to crash. This happened when I tried to build with "test_user_copy" module. With this fix, it prints lots of warnings like this: WARNING: modpost: lib/test_user_copy: section mismatch in reference: (unknown)+0x4 (section: .text.fixup) -> (unknown) (section: .init.text) masahiroy@kernel.org: The issue is reproduced with ARCH=arm allnoconfig + CONFIG_MODULES=y + CONFIG_RUNTIME_TESTING_MENU=y + CONFIG_TEST_USER_COPY=m Signed-off-by: Max Kellermann Signed-off-by: Masahiro Yamada Signed-off-by: Sasha Levin --- scripts/mod/modpost.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index 7d53942445d7..269bd79bcd9a 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -1098,7 +1098,9 @@ static void default_mismatch_handler(const char *modname, struct elf_info *elf, sec_mismatch_count++; warn("%s: section mismatch in reference: %s+0x%x (section: %s) -> %s (section: %s)\n", - modname, fromsym, (unsigned int)(faddr - from->st_value), fromsec, tosym, tosec); + modname, fromsym, + (unsigned int)(faddr - (from ? from->st_value : 0)), + fromsec, tosym, tosec); if (mismatch->mismatch == EXTABLE_TO_NON_TEXT) { if (match(tosec, mismatch->bad_tosec))