From 78aa659979b02afeb26ec51742559e516a2ba41e Mon Sep 17 00:00:00 2001
From: "kaa@polly.(none)" <>
Date: Wed, 24 Oct 2007 21:16:20 +0400
Subject: Fix for bug #31566: my_write(fd, 0x0, 0, flags) fails with EFAULT on
 some platforms

Since the behavior of write(fd, buf, 0) is undefined, it may fail with
EFAULT on some architectures when buf == NULL. The error was propagated
up to a caller, since my_write() code did not handle it properly.

Fixed by checking the 'number of bytes' argument in my_write() and
returning before calling the write() system call when there is nothing
to write.
---
 mysys/my_write.c | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'mysys/my_write.c')

diff --git a/mysys/my_write.c b/mysys/my_write.c
index 4c3d187e4e8..08d70accd57 100644
--- a/mysys/my_write.c
+++ b/mysys/my_write.c
@@ -29,6 +29,10 @@ uint my_write(int Filedes, const byte *Buffer, uint Count, myf MyFlags)
 		   Filedes, (long) Buffer, Count, MyFlags));
   errors=0; written=0L;
 
+  /* The behavior of write(fd, buf, 0) is not portable */
+  if (unlikely(!Count))
+    return 0;
+  
   for (;;)
   {
     if ((writenbytes = (uint) write(Filedes, Buffer, Count)) == Count)
-- 
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