modpost: fix null pointer dereference

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

Max Kellermann committed 2 years ago

Commit 23dfd911 parent 44929bf1 file · +3 −1Browse files

Showing the changes to scripts (1 of 1 file). Show all

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scripts/mod/modpost.c+3−1

@@ -1050,7 +1050,9 @@ static void default_mismatch_handler(const char modname, struct elf_info elf, · 1049 unmodified lines
1050	1050	sec_mismatch_count++;
1051	1051
1052	1052	warn("%s: section mismatch in reference: %s+0x%x (section: %s) -> %s (section: %s)\n",
1053		− modname, fromsym, (unsigned int)(faddr - from->st_value), fromsec, tosym, tosec);
	1053	+ modname, fromsym,
	1054	+ (unsigned int)(faddr - (from ? from->st_value : 0)),
	1055	+ fromsec, tosym, tosec);
1054	1056
1055	1057	if (mismatch->mismatch == EXTABLE_TO_NON_TEXT) {
1056	1058	if (match(tosec, mismatch->bad_tosec))