fs: Simplify new position calculation in lseek()

All these checks are really testing is that resulting position is
within [0; f->size] interval. Convert all of the custom checks into a
signle one done after the switch statement to simplify the code.

Note this change also disables the validity check for f->size ==
FILE_SIZE_STREAM and whence == SEEK_END, but lseek(stream_fd, offset,
SEEK_END) wasn't a meaningful operation to begin with, so this
shouldn't be a problem.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 8 insertions, 11 deletions

diff --git a/fs/fs.c b/fs/fs.c
index 263707c8ff..4ec9c7a842 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -418,26 +418,23 @@ loff_t lseek(int fildes, loff_t offset, int whence)
 
 	switch (whence) {
 	case SEEK_SET:
-		if (f->size != FILE_SIZE_STREAM && offset > f->size)
-			goto out;
-		if (offset < 0)
-			goto out;
-		pos = offset;
+		pos = 0;
 		break;
 	case SEEK_CUR:
-		if (f->size != FILE_SIZE_STREAM && offset + f->pos > f->size)
-			goto out;
-		pos = f->pos + offset;
+		pos = f->pos;
 		break;
 	case SEEK_END:
-		if (offset > 0)
-			goto out;
-		pos = f->size + offset;
+		pos = f->size;
 		break;
 	default:
 		goto out;
 	}
 
+	pos += offset;
+
+	if (f->size != FILE_SIZE_STREAM && (pos < 0 || pos > f->size))
+		goto out;
+
 	if (fsdrv->lseek) {
 		ret = fsdrv->lseek(&f->fsdev->dev, f, pos);
 		if (ret < 0)