[PATCH 1/2] kconfig: preserve the final answer when input has no newline

[Erkan Erdem <hexvalid@gmail.com>]

conf_string() unconditionally removes the last character returned by
fgets(), assuming that it is a newline. When redirected input ends
without a newline, the last character is part of the answer instead.
For example, feeding 42 to an integer prompt stores 4, and feeding
0xff to a hexadecimal prompt stores 0xf. Both commands succeed despite
silently changing the supplied value.

Strip the newline with strcspn() so that a complete answer at EOF is
preserved. Keep the existing handling of newline-terminated and empty
answers unchanged.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Assisted-by: LLM
Signed-off-by: Erkan Erdem <hexvalid@gmail.com>
---

An AI coding assistant found the issue, prepared the fix and changelog,
and ran the verification below after a request to find reproducible
functional bugs in Linux development tools.

Validation:
- Built conf with Clang on macOS and GCC in an x86_64 Linux container,
  using -Wall -Wmissing-prototypes -Wstrict-prototypes -Werror.
- Ran 60 before/after executions on each platform, covering oldaskconfig
  and oldconfig with string, int and hex answers. Unterminated answers
  retain their last character. Newline, empty-answer, empty-input and
  CRLF controls keep the same results.
- The 21 existing Kconfig tests pass on macOS.
- This tests the host configuration tool; a complete kernel was not built.

 scripts/kconfig/conf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/kconfig/conf.c b/scripts/kconfig/conf.c
index fe8ba09b..46c9ca64 100644
--- a/scripts/kconfig/conf.c
+++ b/scripts/kconfig/conf.c
@@ -343,7 +343,7 @@ static int conf_string(struct menu *menu)
 			}
 			/* fall through */
 		default:
-			line[strlen(line)-1] = 0;
+			line[strcspn(line, "\n")] = 0;
 			def = line;
 		}
 		if (def && sym_set_string_value(sym, def))

base-commit: 4d7d9486c04d917265f64c55bd23b2cc4fe7749c
-- 
2.50.1 (Apple Git-155)