fix: use correct ioctl wrapper for create_device
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ShadowCurse
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fix: use correct ioctl wrapper for `create_device` Use `ioctl_with_mut_ref` instead of `ioctl_with_ref` in the `create_device` method as it needs to write to the `kvm_create_device` struct passed to it. This incorrect usage of `ioctl_with_ref` causes newer versions of Rust compiler (1.82 and above) to treat the `kvm_create_device` struct as read-only and bypass following reads from it. This optimization lead to incorrect value being passed to the `File::from_raw_fd` call. Signed-off-by: Egor Lazarchuk <[email protected]>
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ShadowCurse
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| pub fn create_device(&self, device: &mut kvm_create_device) -> Result<DeviceFd> { | ||
| // SAFETY: Safe because we are calling this with the VM fd and we trust the kernel. | ||
| let ret = unsafe { ioctl_with_ref(self, KVM_CREATE_DEVICE(), device) }; | ||
| let ret = unsafe { ioctl_with_mut_ref(self, KVM_CREATE_DEVICE(), device) }; |
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Can you add a test that would trigger the error? As we discussed offline this would not be triggering in the CI because we're not using the latest Rust version. It's enough if we can trigger it locally because eventually we'll be using the latest version in the CI as well.
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We already have tests which can trigger this behavior. Tests are: test_register_unregister_irqfd and test_set_irq_line.
This was referenced Dec 9, 2024
roypat
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Dec 9, 2024
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Probably worth it to check all other uses of ioctl_with_ref for their correctness, but let's not block this fix on that.
rbradford
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Dec 9, 2024
This was referenced Dec 9, 2024
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Summary of the PR
Use
ioctl_with_mut_refinstead ofioctl_with_refforcreate_deviceas it needs to write to thekvm_create_devicestruct passed to it.This incorrect usage of the
ioctl_with_refcauses an issue if used with Rust version 1.82(and later) inreleasebuilds. In those cases thekvm_create_devicestruct is considered to be immutable and the followingFile::from_raw_fdcreates a file from an initial value set in thekvm_create_devicebefore the call.The reason unit tests don't fail in CI is because it uses 1.80.1 version and does not run unit tests with
--releaseoption which does not produce the error.Requirements
Before submitting your PR, please make sure you addressed the following
requirements:
git commit -s), and the commit message has max 60 characters for thesummary and max 75 characters for each description line.
test.
Release" section of CHANGELOG.md (if no such section exists, please create one).
unsafecode is properly documented.