From 595b2a42375427a254ad5a8c85870efea839a9b9 Mon Sep 17 00:00:00 2001
From: Rich Salz <rsalz@openssl.org>
Date: Fri, 28 Apr 2017 14:14:59 -0400
Subject: [PATCH] Check fflush on BIO_ctrl call
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Bug found and fix suggested by Julian Rüth.
Push error if fflush fails

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3266)
---
 crypto/bio/bss_file.c | 13 +++++++++----
 crypto/err/err.c      |  1 +
 include/openssl/err.h |  1 +
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/crypto/bio/bss_file.c b/crypto/bio/bss_file.c
index adf935f350..ae9867e037 100644
--- a/crypto/bio/bss_file.c
+++ b/crypto/bio/bss_file.c
@@ -190,6 +190,7 @@ static long file_ctrl(BIO *b, int cmd, long num, void *ptr)
     FILE *fp = (FILE *)b->ptr;
     FILE **fpp;
     char p[4];
+    int st;
 
     switch (cmd) {
     case BIO_C_FILE_SEEK:
@@ -317,10 +318,14 @@ static long file_ctrl(BIO *b, int cmd, long num, void *ptr)
         b->shutdown = (int)num;
         break;
     case BIO_CTRL_FLUSH:
-        if (b->flags & BIO_FLAGS_UPLINK)
-            UP_fflush(b->ptr);
-        else
-            fflush((FILE *)b->ptr);
+        st = b->flags & BIO_FLAGS_UPLINK
+                ? UP_fflush(b->ptr) : fflush((FILE *)b->ptr);
+        if (st == EOF) {
+            SYSerr(SYS_F_FFLUSH, get_last_sys_error());
+            ERR_add_error_data(1, "fflush()");
+            BIOerr(BIO_F_FILE_CTRL, ERR_R_SYS_LIB);
+            ret = 0;
+        }
         break;
     case BIO_CTRL_DUP:
         ret = 1;
diff --git a/crypto/err/err.c b/crypto/err/err.c
index d5cad0577e..f866f2fdd0 100644
--- a/crypto/err/err.c
+++ b/crypto/err/err.c
@@ -82,6 +82,7 @@ static ERR_STRING_DATA ERR_str_functs[] = {
     {ERR_PACK(0, SYS_F_GETSOCKOPT, 0), "getsockopt"},
     {ERR_PACK(0, SYS_F_GETSOCKNAME, 0), "getsockname"},
     {ERR_PACK(0, SYS_F_GETHOSTBYNAME, 0), "gethostbyname"},
+    {ERR_PACK(0, SYS_F_FFLUSH, 0), "fflush"},
     {0, NULL},
 };
 
diff --git a/include/openssl/err.h b/include/openssl/err.h
index 9bbe9e1091..29a261ceb7 100644
--- a/include/openssl/err.h
+++ b/include/openssl/err.h
@@ -159,6 +159,7 @@ typedef struct err_state_st {
 # define SYS_F_GETSOCKOPT        15
 # define SYS_F_GETSOCKNAME       16
 # define SYS_F_GETHOSTBYNAME     17
+# define SYS_F_FFLUSH            18
 
 /* reasons */
 # define ERR_R_SYS_LIB   ERR_LIB_SYS/* 2 */
-- 
2.25.1