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kconfig: fix infinite loop in sym_calc_choice()

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Since commit f79dc03fe6 ("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: f79dc03fe6 ("kconfig: refactor choice value calculation")
Reported-by: Marco Bonelli <marco@mebeim.net>
Closes: https://lore.kernel.org/all/1763151587.3581913.1727224126288@privateemail.com/
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
This commit is contained in:
Masahiro Yamada 2024-09-25 20:25:31 +09:00
parent 7fb1d1e038
commit 4d46b5b623
1 changed files with 8 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
scripts/kconfig/parser.y
View File

@ -159,8 +159,14 @@ config_stmt: config_entry_start config_option_list
yynerrs++;
}
list_add_tail(&current_entry->sym->choice_link,
&current_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(&current_entry->sym->choice_link))
list_add_tail(&current_entry->sym->choice_link,
&current_choice->choice_members);
}
printd(DEBUG_PARSE, "%s:%d:endconfig\n", cur_filename, cur_lineno);