From 4d46b5b623e0adee1153b1d80689211e5094ae44 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Wed, 25 Sep 2024 20:25:31 +0900 Subject: kconfig: fix infinite loop in sym_calc_choice() Since commit f79dc03fe68c ("kconfig: refactor choice value calculation"), Kconfig for ARCH=powerpc may result in an infinite loop. This occurs because there are two entries for POWERPC64_CPU in a choice block. If the same symbol appears twice in a choice block, the ->choice_link node is added twice to ->choice_members, resulting a corrupted linked list. A simple test case is: choice prompt "choice" config A bool "A" config B bool "B 1" config B bool "B 2" endchoice Running 'make defconfig' results in an infinite loop. One solution is to replace the current two entries: config POWERPC64_CPU bool "Generic (POWER5 and PowerPC 970 and above)" depends on PPC_BOOK3S_64 && !CPU_LITTLE_ENDIAN select PPC_64S_HASH_MMU config POWERPC64_CPU bool "Generic (POWER8 and above)" depends on PPC_BOOK3S_64 && CPU_LITTLE_ENDIAN select ARCH_HAS_FAST_MULTIPLIER select PPC_64S_HASH_MMU select PPC_HAS_LBARX_LHARX with the following single entry: config POWERPC64_CPU bool "Generic 64 bit powerpc" depends on PPC_BOOK3S_64 select ARCH_HAS_FAST_MULTIPLIER if CPU_LITTLE_ENDIAN select PPC_64S_HASH_MMU select PPC_HAS_LBARX_LHARX if CPU_LITTLE_ENDIAN In my opinion, the latter looks cleaner, but PowerPC maintainers may prefer to display different prompts depending on CPU_LITTLE_ENDIAN. For now, this commit fixes the issue in Kconfig, restoring the original behavior. I will reconsider whether such a use case is worth supporting. Fixes: f79dc03fe68c ("kconfig: refactor choice value calculation") Reported-by: Marco Bonelli Closes: https://lore.kernel.org/all/1763151587.3581913.1727224126288@privateemail.com/ Signed-off-by: Masahiro Yamada --- scripts/kconfig/parser.y | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/scripts/kconfig/parser.y b/scripts/kconfig/parser.y index 1ad60f9e164e..bc43fb67c7c4 100644 --- a/scripts/kconfig/parser.y +++ b/scripts/kconfig/parser.y @@ -159,8 +159,14 @@ config_stmt: config_entry_start config_option_list yynerrs++; } - list_add_tail(¤t_entry->sym->choice_link, - ¤t_choice->choice_members); + /* + * If the same symbol appears twice in a choice block, the list + * node would be added twice, leading to a broken linked list. + * list_empty() ensures that this symbol has not yet added. + */ + if (list_empty(¤t_entry->sym->choice_link)) + list_add_tail(¤t_entry->sym->choice_link, + ¤t_choice->choice_members); } printd(DEBUG_PARSE, "%s:%d:endconfig\n", cur_filename, cur_lineno); -- cgit v1.2.3