From: Florian Weimer <fweimer@redhat.com>
Date: Fri, 18 Mar 2022 20:27:54 +0000 (+0100)
Subject: libio: Flush-only _IO_str_overflow must not return EOF (bug 28949)
X-Git-Tag: glibc-2.36~487
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=88ed43ff0cf2561481de7cba00686386794515d6;p=thirdparty%2Fglibc.git

libio: Flush-only _IO_str_overflow must not return EOF (bug 28949)

In general, _IO_str_overflow returns the character passed as an argument
on success.  However, if flush-only operation is requested by passing
EOF, returning EOF looks like an error, and the caller cannot tell
whether the operation was successful or not.

_IO_wstr_overflow had the same bug regarding WEOF.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
---

diff --git a/libio/strops.c b/libio/strops.c
index 6a9a8846c43..1cd0bf6c3d1 100644
--- a/libio/strops.c
+++ b/libio/strops.c
@@ -133,7 +133,10 @@ _IO_str_overflow (FILE *fp, int c)
     *fp->_IO_write_ptr++ = (unsigned char) c;
   if (fp->_IO_write_ptr > fp->_IO_read_end)
     fp->_IO_read_end = fp->_IO_write_ptr;
-  return c;
+  if (flush_only)
+    return 0;
+  else
+    return c;
 }
 libc_hidden_def (_IO_str_overflow)
 
diff --git a/libio/wstrops.c b/libio/wstrops.c
index 8e44f86c35a..2aec3149375 100644
--- a/libio/wstrops.c
+++ b/libio/wstrops.c
@@ -130,7 +130,10 @@ _IO_wstr_overflow (FILE *fp, wint_t c)
     *fp->_wide_data->_IO_write_ptr++ = c;
   if (fp->_wide_data->_IO_write_ptr > fp->_wide_data->_IO_read_end)
     fp->_wide_data->_IO_read_end = fp->_wide_data->_IO_write_ptr;
-  return c;
+  if (flush_only)
+    return 0;
+  else
+    return c;
 }