[PATCH v1 2/2] xstrtol: Add defensive check against undocumented errors

[Alejandro Colomar <alx@kernel.org>]

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strtod(3) calls malloc(3) in some systems.  While strtol(3) doesn't,
let's be cautious and write code that would be safe under a theoretical
implementation of strtol(3) that could ENOMEM (and let's assume we don't
know what 'e' will look like after such an error).

Some attempt of defensive error handling had been added in 790855e18a1d,
but it was wrong, since it was assuming e!=nptr on such a case, which is
not a reasonable assumption.

Fixes: 790855e18a1d (2003-10-14, "Handle invalid suffixes and overflow independently, so that ...")
Cc: Paul Eggert <eggert@cs.ucla.edu>
Cc: Bruno Haible <bruno@clisp.org>
Cc: Đoàn Trần Công Danh <congdanhqx@gmail.com>
Cc: Eli Schwartz <eschwartz93@gmail.com>
Cc: Sam James <sam@gentoo.org>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Iker Pedrosa <ipedrosa@redhat.com>
Cc: Michael Vetter <jubalh@iodoru.org>
Cc: <liba2i@lists.linux.dev>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
---
 lib/xstrtol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/xstrtol.c b/lib/xstrtol.c
index 592673557f..faa7b9fd4c 100644
--- a/lib/xstrtol.c
+++ b/lib/xstrtol.c
@@ -94,7 +94,7 @@ __xstrtol (char const *nptr, char **endptr, int base,
   if (endptr && e)
     *endptr = e;
 
-  if (e == nptr)
+  if (e == nptr && (errno == 0 || errno == EINVAL))
     {
       /* If there is no number but there is a valid suffix, assume the
          number is 1.  The string is invalid otherwise.  */
-- 
2.45.2


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