1 files changed, 26 insertions, 1 deletions

diff --git a/lib/libc/stdio/fvwrite.c b/lib/libc/stdio/fvwrite.c
index 82a49cb14986..efcfffbaf4e0 100644
--- a/lib/libc/stdio/fvwrite.c
+++ b/lib/libc/stdio/fvwrite.c
@@ -64,7 +64,7 @@ __sfvwrite(fp, uio)
 	register struct __siov *iov;
 	register int w, s;
 	char *nl;
-	int nlknown, nldist;
+	int nlknown, nldist, firsttime;
 
 	if ((len = uio->uio_resid) == 0)
 		return (0);
@@ -86,12 +86,21 @@ __sfvwrite(fp, uio)
 		len = iov->iov_len; \
 		iov++; \
 	}
+	firsttime = 1;
 	if (fp->_flags & __SNBF) {
 		/*
 		 * Unbuffered: write up to BUFSIZ bytes at a time.
 		 */
 		do {
 			GETIOV(;);
+			if (firsttime) {
+				if ((fp->_flags & __SAPP) &&
+				    _sseek(fp, (fpos_t)0, SEEK_END) == -1)
+					goto err;
+				/* In case FAPPEND mode is set. */
+				fp->_flags &= ~__SOFF;
+				firsttime = 0;
+			}
 			w = (*fp->_write)(fp->_cookie, p, MIN(len, BUFSIZ));
 			if (w <= 0)
 				goto err;
@@ -147,6 +156,14 @@ __sfvwrite(fp, uio)
 					goto err;
 			} else if (len >= (w = fp->_bf._size)) {
 				/* write directly */
+				if (firsttime) {
+					if ((fp->_flags & __SAPP) &&
+					    _sseek(fp, (fpos_t)0, SEEK_END) == -1)
+						goto err;
+					/* In case FAPPEND mode is set. */
+					fp->_flags &= ~__SOFF;
+					firsttime = 0;
+				}
 				w = (*fp->_write)(fp->_cookie, p, w);
 				if (w <= 0)
 					goto err;
@@ -186,6 +203,14 @@ __sfvwrite(fp, uio)
 				if (__fflush(fp))
 					goto err;
 			} else if (s >= (w = fp->_bf._size)) {
+				if (firsttime) {
+					if ((fp->_flags & __SAPP) &&
+					    _sseek(fp, (fpos_t)0, SEEK_END) == -1)
+						goto err;
+					/* In case FAPPEND mode is set. */
+					fp->_flags &= ~__SOFF;
+					firsttime = 0;
+				}
 				w = (*fp->_write)(fp->_cookie, p, w);
 				if (w <= 0)
 				 	goto err;