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

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

[Erkan Erdem]

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)

[PATCH 2/2] checkkconfigsymbols: resolve revisions before resetting the tree

[Erkan Erdem]

The commit comparison resets the current branch to commit_a before
resolving commit_b. If the second revision is HEAD or the current branch
name, it then resolves to the first revision. For example, --diff
HEAD^..HEAD compares the parent with itself and silently misses newly
undefined symbols. The same problem affects --commit with the current
branch name.

Resolve and verify both revisions as commits before the first reset.
This keeps their meaning stable throughout the comparison and rejects
invalid endpoints before changing the working tree.

Keep lookup diagnostics separate from the resolved hashes. Use the
resolved range for --find too, since resetting also updates ORIG_HEAD.

Fixes: b1a3f243485f ("checkkconfigsymbols.py: make it Git aware")
Link: https://lore.kernel.org/20210901145212.478066-1-arielmarcovitch@gmail.com/
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:
- Ran the actual CLI against disposable Git repositories, comparing the
  original script with the patched source. All 15 patched cases pass.
- Covered HEAD-relative ranges, branch names, hashes, tags, annotated
  tags, ambiguous branch/tag names, identical revisions, --commit,
  --find, ORIG_HEAD and invalid or non-commit endpoints.
- Checked HEAD, current branch, index and tracked file contents after
  every invocation. The patched cases preserve these values, including
  when the second revision is invalid.

 scripts/checkkconfigsymbols.py | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/scripts/checkkconfigsymbols.py b/scripts/checkkconfigsymbols.py
index 36c920e7..e0a1a631 100755
--- a/scripts/checkkconfigsymbols.py
+++ b/scripts/checkkconfigsymbols.py
@@ -150,6 +150,13 @@ def print_undefined_symbols():
             undefined_a = {}
             undefined_b = {}
 
+        commit_a = execute(["git", "rev-parse", "--verify", commit_a + "^{commit}"],
+                           stderr=None).strip()
+        commit_b = execute(["git", "rev-parse", "--verify", commit_b + "^{commit}"],
+                           stderr=None).strip()
+        if args.diff:
+            args.diff = commit_a + ".." + commit_b
+
         # get undefined items before the commit
         reset(commit_a)
         undefined_a, _ = check_symbols(args.ignore)
@@ -223,10 +230,10 @@ def red(string):
     return "\033[31m%s\033[0m" % string if COLOR else string
 
 
-def execute(cmd):
+def execute(cmd, stderr=subprocess.STDOUT):
     """Execute %cmd and return stdout.  Exit in case of error."""
     try:
-        stdout = subprocess.check_output(cmd, stderr=subprocess.STDOUT, shell=False)
+        stdout = subprocess.check_output(cmd, stderr=stderr, shell=False)
         stdout = stdout.decode(errors='replace')
     except subprocess.CalledProcessError as fail:
         exit(fail)
-- 
2.50.1 (Apple Git-155)

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

[Julian Braha]

Hi Erkan,

I see that this is your first patch submission to the kernel. Welcome!

First thing, if you run the ./scripts/get_maintainer.pl check on this
patch, it should list a few more people to CC.

On 9/5/26 13:32, Erkan Erdem wrote:
> 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.

Since you already have some tests, it would be good to add a basic test
for this in scripts/kconfig/tests.

Kconfig doesn't have as many tests as it should, and it's been
complained about by some core maintainers in the past [1].

> 
>  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

Otherwise this change looks good to me (and is more readable).

Link: https://lore.kernel.org/all/20180206093803.GC31558@kroah.com/ [1]

- Julian Braha

Re: [PATCH 2/2] checkkconfigsymbols: resolve revisions before resetting the tree

[Julian Braha]

On 9/5/26 13:32, Erkan Erdem wrote:
> The commit comparison resets the current branch to commit_a before
> resolving commit_b. If the second revision is HEAD or the current branch
> name, it then resolves to the first revision. For example, --diff
> HEAD^..HEAD compares the parent with itself and silently misses newly
> undefined symbols. The same problem affects --commit with the current
> branch name.
> 
> Resolve and verify both revisions as commits before the first reset.
> This keeps their meaning stable throughout the comparison and rejects
> invalid endpoints before changing the working tree.
> 
> Keep lookup diagnostics separate from the resolved hashes. Use the
> resolved range for --find too, since resetting also updates ORIG_HEAD.
> 
> Fixes: b1a3f243485f ("checkkconfigsymbols.py: make it Git aware")
> Link: https://lore.kernel.org/20210901145212.478066-1-arielmarcovitch@gmail.com/
> 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:
> - Ran the actual CLI against disposable Git repositories, comparing the
>   original script with the patched source. All 15 patched cases pass.
> - Covered HEAD-relative ranges, branch names, hashes, tags, annotated
>   tags, ambiguous branch/tag names, identical revisions, --commit,
>   --find, ORIG_HEAD and invalid or non-commit endpoints.
> - Checked HEAD, current branch, index and tracked file contents after
>   every invocation. The patched cases preserve these values, including
>   when the second revision is invalid.
> 
>  scripts/checkkconfigsymbols.py | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/checkkconfigsymbols.py b/scripts/checkkconfigsymbols.py
> index 36c920e7..e0a1a631 100755
> --- a/scripts/checkkconfigsymbols.py
> +++ b/scripts/checkkconfigsymbols.py
> @@ -150,6 +150,13 @@ def print_undefined_symbols():
>              undefined_a = {}
>              undefined_b = {}
>  
> +        commit_a = execute(["git", "rev-parse", "--verify", commit_a + "^{commit}"],
> +                           stderr=None).strip()
> +        commit_b = execute(["git", "rev-parse", "--verify", commit_b + "^{commit}"],
> +                           stderr=None).strip()
> +        if args.diff:
> +            args.diff = commit_a + ".." + commit_b
> +
>          # get undefined items before the commit
>          reset(commit_a)
>          undefined_a, _ = check_symbols(args.ignore)
> @@ -223,10 +230,10 @@ def red(string):
>      return "\033[31m%s\033[0m" % string if COLOR else string
>  
>  
> -def execute(cmd):
> +def execute(cmd, stderr=subprocess.STDOUT):
>      """Execute %cmd and return stdout.  Exit in case of error."""
>      try:
> -        stdout = subprocess.check_output(cmd, stderr=subprocess.STDOUT, shell=False)
> +        stdout = subprocess.check_output(cmd, stderr=stderr, shell=False)
>          stdout = stdout.decode(errors='replace')
>      except subprocess.CalledProcessError as fail:
>          exit(fail)

This patch is unrelated to your patch 1/2, so they should be sent
separately.

Sets of patches are intended for changes that depend on each other, or
at least are closely related.

- Julian Braha