ide: fix drive head toctou bug on enlightened path#3535
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smalis-msft
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May 20, 2026
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Pull request overview
Fixes a TOCTOU-style correctness issue in the IDE “enlightened INT13” fast path by ensuring the busy/error gating check is performed against the drive selected by the packet’s device_head value, rather than the previously-selected drive.
Changes:
- Move the drive busy/error gating logic to occur after writing
DeviceHead, so status is checked for the intended drive. - Keep the enlightened-path early-bail behavior for busy/DRQ/error states (now applied to the correct drive).
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| self.write_drive_register( | ||
| DriveRegister::DeviceHead, | ||
| eint13_cmd.device_head.into(), | ||
| bus_master_state, | ||
| ); |
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| if let Some(status) = self.current_drive_status() { | ||
| if status.err() { | ||
| tracelimit::warn_ratelimited!( | ||
| "drive is in error state, ignoring enlightened command", | ||
| ); |
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The enlightened path in the IDE implementation is supposed to check whether the drive is busy, and bail out if so.
We are currently checking if the drive is busy before switching the device head, meaning we can mistakenly go further down the enlightened path, even when the drive is busy.