Help to recover from bad seek (i.e. negative or too big) happens beyond

our pre-check control. Do the same way as refill.c does when it set __SERR,
i.e. clear read and ungetc buffers. Clear EOF flag too.

2 files changed, 12 insertions, 5 deletions

diff --git a/lib/libc/stdio/fseek.c b/lib/libc/stdio/fseek.c
index 2278f31..9dc8bd2 100644
--- a/lib/libc/stdio/fseek.c
+++ b/lib/libc/stdio/fseek.c
@@ -297,11 +297,6 @@ abspos:
 dumb:
 	if (__sflush(fp) || _sseek(fp, (fpos_t)offset, whence) == POS_ERR)
 		return (-1);
-	if (ltest && fp->_offset > LONG_MAX) {
-		fp->_flags |= __SERR;
-		errno = EOVERFLOW;
-		return (-1);
-	}
 	/* success: clear EOF indicator and discard ungetc() data */
 	if (HASUB(fp))
 		FREEUB(fp);
@@ -309,5 +304,10 @@ dumb:
 	fp->_r = 0;
 	/* fp->_w = 0; */	/* unnecessary (I think...) */
 	fp->_flags &= ~__SEOF;
+	if (ltest && fp->_offset > LONG_MAX) {
+		fp->_flags |= __SERR;
+		errno = EOVERFLOW;
+		return (-1);
+	}
 	return (0);
 }
diff --git a/lib/libc/stdio/stdio.c b/lib/libc/stdio/stdio.c
index 4bee608..7f66fa8 100644
--- a/lib/libc/stdio/stdio.c
+++ b/lib/libc/stdio/stdio.c
@@ -171,6 +171,13 @@ _sseek(fp, offset, whence)
 	 */
 	if (ret < 0) {
 		if (errret == 0) {
+			if (offset != 0 || whence != SEEK_CUR) {
+				if (HASUB(fp))
+					FREEUB(fp);
+				fp->_p = fp->_bf._base;
+				fp->_r = 0;
+				fp->_flags &= ~__SEOF;
+			}
 			fp->_flags |= __SERR;
 			errno = EINVAL;
 		} else if (errret == ESPIPE)