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virtio-devices: fix UB getting tty size

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TIOCGWINSZ modifies its argument, so it needs to mutably borrow it.
Unfortunately, ioctl()'s signature is not able to enforce this, and
the write happens in the kernel, so I don't think anything like miri,
valgrind, UBSan, etc. would have been able to catch this.

The UB passing an immutable reference caused resulted, for me, in
get_win_size() returning (0, 0) since LLVM commit
9a09c737a052 ("[BasicAA] Make isNotCapturedBeforeOrAt() check for
calls more precise (#69931)").

I've had a look through the other ioctl() calls in Cloud Hypervisor,
and I don't think any others have the same problem.

Signed-off-by: Alyssa Ross <hi@alyssa.is>
This commit is contained in:
Alyssa Ross 2024-07-03 22:30:02 +02:00 committed by Liu Wei
parent b5cce0d371
commit e7c7a304e8
1 changed files with 2 additions and 2 deletions
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4
virtio-devices/src/console.rs
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@ -608,11 +608,11 @@ fn get_win_size(tty: &dyn AsRawFd) -> (u16, u16) {
xpixel: u16,
ypixel: u16,
}
let ws: WindowSize = WindowSize::default();
let mut ws: WindowSize = WindowSize::default();
// SAFETY: FFI call with correct arguments
unsafe {
libc::ioctl(tty.as_raw_fd(), TIOCGWINSZ, &ws);
libc::ioctl(tty.as_raw_fd(), TIOCGWINSZ, &mut ws);
}
(ws.cols, ws.rows)