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Fixes overflow in libstd/io/cursor.rs "seek" #39874

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merged 2 commits into from
Feb 21, 2017
Merged

Fixes overflow in libstd/io/cursor.rs "seek" #39874

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ab57e7b
std::io::cursor Added test for seeking beyond i64.
amosonn Feb 16, 2017
a2d176e
std::io::cursor: Fixed Seek so test passes.
amosonn Feb 16, 2017
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59 changes: 49 additions & 10 deletions src/libstd/io/cursor.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -200,18 +200,20 @@ impl<T> Cursor<T> {
#[stable(feature = "rust1", since = "1.0.0")]
impl<T> io::Seek for Cursor<T> where T: AsRef<[u8]> {
fn seek(&mut self, style: SeekFrom) -> io::Result<u64> {
let pos = match style {
SeekFrom::Start(n) => { self.pos = n; return Ok(n) }
SeekFrom::End(n) => self.inner.as_ref().len() as i64 + n,
SeekFrom::Current(n) => self.pos as i64 + n,
let (base_pos, offset) = match style {
SeekFrom::Start(n) => { self.pos = n; return Ok(n); }
SeekFrom::End(n) => (self.inner.as_ref().len() as u64, n),
SeekFrom::Current(n) => (self.pos, n),
};

if pos < 0 {
Err(Error::new(ErrorKind::InvalidInput,
"invalid seek to a negative position"))
let new_pos = if offset >= 0 {
base_pos.checked_add(offset as u64)
} else {
self.pos = pos as u64;
Ok(self.pos)
base_pos.checked_sub((offset.wrapping_neg()) as u64)
};
match new_pos {
Some(n) => {self.pos = n; Ok(self.pos)}
None => Err(Error::new(ErrorKind::InvalidInput,
"invalid seek to a negative or overflowing position"))
}
}
}
Expand Down Expand Up @@ -526,6 +528,43 @@ mod tests {
assert_eq!(r.write(&[3]).unwrap(), 0);
}

#[test]
fn seek_past_i64() {
let buf = [0xff];
let mut r = Cursor::new(&buf[..]);
assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);

let mut r = Cursor::new(vec![10]);
assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);

let mut buf = [0];
let mut r = Cursor::new(&mut buf[..]);
assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);

let mut r = Cursor::new(vec![10].into_boxed_slice());
assert_eq!(r.seek(SeekFrom::Start(6)).unwrap(), 6);
assert_eq!(r.seek(SeekFrom::Current(0x7ffffffffffffff0)).unwrap(), 0x7ffffffffffffff6);
assert_eq!(r.seek(SeekFrom::Current(0x10)).unwrap(), 0x8000000000000006);
assert_eq!(r.seek(SeekFrom::Current(0)).unwrap(), 0x8000000000000006);
assert!(r.seek(SeekFrom::Current(0x7ffffffffffffffd)).is_err());
assert_eq!(r.seek(SeekFrom::Current(-0x8000000000000000)).unwrap(), 6);
}

#[test]
fn seek_before_0() {
let buf = [0xff];
Expand Down