[PATCH] modpost: do not make find_tosym() return NULL

[Masahiro Yamada <masahiroy@kernel.org>]

As mentioned in commit 397586506c3d ("modpost: Add '.ltext' and
'.ltext.*' to TEXT_SECTIONS"), modpost can result in a segmentation
fault due to a NULL pointer dereference in default_mismatch_handler().

find_tosym() does not need to return the NULL pointer. It can return
the original symbol pointer if a better one is not found.

This fixes the reported segmentation fault.

Fixes: a23e7584ecf3 ("modpost: unify 'sym' and 'to' in default_mismatch_handler()")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

 scripts/mod/modpost.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 6b37039c9e92..2f5b91da5afa 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1007,6 +1007,8 @@ static Elf_Sym *find_fromsym(struct elf_info *elf, Elf_Addr addr,
 
 static Elf_Sym *find_tosym(struct elf_info *elf, Elf_Addr addr, Elf_Sym *sym)
 {
+	Elf_Sym *new_sym;
+
 	/* If the supplied symbol has a valid name, return it */
 	if (is_valid_name(elf, sym))
 		return sym;
@@ -1015,8 +1017,9 @@ static Elf_Sym *find_tosym(struct elf_info *elf, Elf_Addr addr, Elf_Sym *sym)
 	 * Strive to find a better symbol name, but the resulting name may not
 	 * match the symbol referenced in the original code.
 	 */
-	return symsearch_find_nearest(elf, addr, get_secindex(elf, sym),
-				      true, 20);
+	new_sym = symsearch_find_nearest(elf, addr, get_secindex(elf, sym),
+					 true, 20);
+	return new_sym ? new_sym : sym;
 }
 
 static bool is_executable_section(struct elf_info *elf, unsigned int secndx)
-- 
2.40.1