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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

Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
This commit is contained in:
Max Kellermann 2024-02-15 15:13:21 +01:00 committed by Masahiro Yamada
parent 44929bface
commit 23dfd914d2
1 changed files with 3 additions and 1 deletions
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4
scripts/mod/modpost.c
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@ -1050,7 +1050,9 @@ 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))