remove `#[disable_initialized_field_access]` by BennoLossin · Pull Request #111 · Rust-for-Linux/pin-init

BennoLossin · 2026-02-27T19:25:31Z

Gary noticed [1] that the initializer macros as well as the [Pin]Init traits cannot support packed struct, since they use operations that require aligned pointers. This means that any code using packed structs and pin-init is unsound.

Thus remove the #[disable_initialized_field_access] attribute from init!, which is the only safe way to create an initializer of a packed struct.

In the future, we can add support for packed structs by changing the trait infrastructure to include UnalignedInit or hopefully another mechanism.

Reported-by: Gary Guo gary@garyguo.net
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1]
Fixes: db96c51 ("add references to previously initialized fields")

nbdd0121 · 2026-02-27T22:25:35Z

The commit that this fixes should be the one that introduced this feature instead? Arguably creating reference is the fix, not the fixed commit.

BennoLossin · 2026-02-28T08:30:05Z

Yeah you're right, fixed it. Both my kernel tests & the intel kernel CI also reported no issues, so I'll send this to the list as well.

Gary noticed [1] that the initializer macros as well as the `[Pin]Init` traits cannot support unaligned fields, since they use operations that require aligned pointers. This means that any code using structs with unaligned fields in pin-init is unsound. By default, the `init!` macro generates references to initialized fields, which makes the compiler check that those fields are aligned. However, we added the `#[disable_initialized_field_access]` attribute to avoid this behavior in 71988db ("internal: init: add escape hatch for referencing initialized fields"). Thus remove the `#[disable_initialized_field_access]` attribute from `init!`, which is the only safe way to create an initializer handling unaligned fields. If support for in-place initializing structs with unaligned fields is required in the future, we could figure out a solution. This is tracked in [2]. Reported-by: Gary Guo <gary@garyguo.net> Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1] Link: #112 [2] Fixes: 71988db ("internal: init: add escape hatch for referencing initialized fields") Signed-off-by: Benno Lossin <lossin@kernel.org>

The functions `[Pin]Init::__[pinned_]init` and `ptr::write` called from the `init!` macro require the passed pointer to be aligned. This fact is ensured by the creation of field accessors to previously initialized fields. Since we missed this very important fact from the beginning [1], document it in the code. Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1] Signed-off-by: Benno Lossin <lossin@kernel.org>

BennoLossin · 2026-02-27T19:25:31Z

Gary noticed [1] that the initializer macros as well as the [Pin]Init traits cannot support packed struct, since they use operations that require aligned pointers. This means that any code using packed structs and pin-init is unsound.

Thus remove the #[disable_initialized_field_access] attribute from init!, which is the only safe way to create an initializer of a packed struct.

In the future, we can add support for packed structs by changing the trait infrastructure to include UnalignedInit or hopefully another mechanism.

Reported-by: Gary Guo gary@garyguo.net
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1]
Fixes: db96c51 ("add references to previously initialized fields")

nbdd0121 · 2026-02-27T22:25:35Z

The commit that this fixes should be the one that introduced this feature instead? Arguably creating reference is the fix, not the fixed commit.

BennoLossin · 2026-02-28T08:30:05Z

Yeah you're right, fixed it. Both my kernel tests & the intel kernel CI also reported no issues, so I'll send this to the list as well.

Gary noticed [1] that the initializer macros as well as the `[Pin]Init` traits cannot support unaligned fields, since they use operations that require aligned pointers. This means that any code using structs with unaligned fields in pin-init is unsound. By default, the `init!` macro generates references to initialized fields, which makes the compiler check that those fields are aligned. However, we added the `#[disable_initialized_field_access]` attribute to avoid this behavior in 71988db ("internal: init: add escape hatch for referencing initialized fields"). Thus remove the `#[disable_initialized_field_access]` attribute from `init!`, which is the only safe way to create an initializer handling unaligned fields. If support for in-place initializing structs with unaligned fields is required in the future, we could figure out a solution. This is tracked in [2]. Reported-by: Gary Guo <gary@garyguo.net> Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1] Link: #112 [2] Fixes: 71988db ("internal: init: add escape hatch for referencing initialized fields") Signed-off-by: Benno Lossin <lossin@kernel.org>

The functions `[Pin]Init::__[pinned_]init` and `ptr::write` called from the `init!` macro require the passed pointer to be aligned. This fact is ensured by the creation of field accessors to previously initialized fields. Since we missed this very important fact from the beginning [1], document it in the code. Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1] Signed-off-by: Benno Lossin <lossin@kernel.org>

BennoLossin · 2026-02-27T19:25:31Z

Gary noticed [1] that the initializer macros as well as the [Pin]Init traits cannot support packed struct, since they use operations that require aligned pointers. This means that any code using packed structs and pin-init is unsound.

Thus remove the #[disable_initialized_field_access] attribute from init!, which is the only safe way to create an initializer of a packed struct.

In the future, we can add support for packed structs by changing the trait infrastructure to include UnalignedInit or hopefully another mechanism.

Reported-by: Gary Guo gary@garyguo.net
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1]
Fixes: db96c51 ("add references to previously initialized fields")

nbdd0121 · 2026-02-27T22:25:35Z

The commit that this fixes should be the one that introduced this feature instead? Arguably creating reference is the fix, not the fixed commit.

BennoLossin · 2026-02-28T08:30:05Z

Yeah you're right, fixed it. Both my kernel tests & the intel kernel CI also reported no issues, so I'll send this to the list as well.

Gary noticed [1] that the initializer macros as well as the `[Pin]Init` traits cannot support unaligned fields, since they use operations that require aligned pointers. This means that any code using structs with unaligned fields in pin-init is unsound. By default, the `init!` macro generates references to initialized fields, which makes the compiler check that those fields are aligned. However, we added the `#[disable_initialized_field_access]` attribute to avoid this behavior in 71988db ("internal: init: add escape hatch for referencing initialized fields"). Thus remove the `#[disable_initialized_field_access]` attribute from `init!`, which is the only safe way to create an initializer handling unaligned fields. If support for in-place initializing structs with unaligned fields is required in the future, we could figure out a solution. This is tracked in [2]. Reported-by: Gary Guo <gary@garyguo.net> Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1] Link: #112 [2] Fixes: 71988db ("internal: init: add escape hatch for referencing initialized fields") Signed-off-by: Benno Lossin <lossin@kernel.org>

The functions `[Pin]Init::__[pinned_]init` and `ptr::write` called from the `init!` macro require the passed pointer to be aligned. This fact is ensured by the creation of field accessors to previously initialized fields. Since we missed this very important fact from the beginning [1], document it in the code. Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1] Signed-off-by: Benno Lossin <lossin@kernel.org>

BennoLossin · 2026-02-27T19:25:31Z

Gary noticed [1] that the initializer macros as well as the [Pin]Init traits cannot support packed struct, since they use operations that require aligned pointers. This means that any code using packed structs and pin-init is unsound.

Thus remove the #[disable_initialized_field_access] attribute from init!, which is the only safe way to create an initializer of a packed struct.

In the future, we can add support for packed structs by changing the trait infrastructure to include UnalignedInit or hopefully another mechanism.

Reported-by: Gary Guo gary@garyguo.net
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1]
Fixes: db96c51 ("add references to previously initialized fields")

nbdd0121 · 2026-02-27T22:25:35Z

The commit that this fixes should be the one that introduced this feature instead? Arguably creating reference is the fix, not the fixed commit.

BennoLossin · 2026-02-28T08:30:05Z

Yeah you're right, fixed it. Both my kernel tests & the intel kernel CI also reported no issues, so I'll send this to the list as well.

Gary noticed [1] that the initializer macros as well as the `[Pin]Init` traits cannot support unaligned fields, since they use operations that require aligned pointers. This means that any code using structs with unaligned fields in pin-init is unsound. By default, the `init!` macro generates references to initialized fields, which makes the compiler check that those fields are aligned. However, we added the `#[disable_initialized_field_access]` attribute to avoid this behavior in 71988db ("internal: init: add escape hatch for referencing initialized fields"). Thus remove the `#[disable_initialized_field_access]` attribute from `init!`, which is the only safe way to create an initializer handling unaligned fields. If support for in-place initializing structs with unaligned fields is required in the future, we could figure out a solution. This is tracked in [2]. Reported-by: Gary Guo <gary@garyguo.net> Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1] Link: #112 [2] Fixes: 71988db ("internal: init: add escape hatch for referencing initialized fields") Signed-off-by: Benno Lossin <lossin@kernel.org>

The functions `[Pin]Init::__[pinned_]init` and `ptr::write` called from the `init!` macro require the passed pointer to be aligned. This fact is ensured by the creation of field accessors to previously initialized fields. Since we missed this very important fact from the beginning [1], document it in the code. Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1] Signed-off-by: Benno Lossin <lossin@kernel.org>

BennoLossin · 2026-02-27T19:25:31Z

Gary noticed [1] that the initializer macros as well as the [Pin]Init traits cannot support packed struct, since they use operations that require aligned pointers. This means that any code using packed structs and pin-init is unsound.

Thus remove the #[disable_initialized_field_access] attribute from init!, which is the only safe way to create an initializer of a packed struct.

In the future, we can add support for packed structs by changing the trait infrastructure to include UnalignedInit or hopefully another mechanism.

Reported-by: Gary Guo gary@garyguo.net
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1]
Fixes: db96c51 ("add references to previously initialized fields")

nbdd0121 · 2026-02-27T22:25:35Z

The commit that this fixes should be the one that introduced this feature instead? Arguably creating reference is the fix, not the fixed commit.

BennoLossin · 2026-02-28T08:30:05Z

Yeah you're right, fixed it. Both my kernel tests & the intel kernel CI also reported no issues, so I'll send this to the list as well.

Gary noticed [1] that the initializer macros as well as the `[Pin]Init` traits cannot support unaligned fields, since they use operations that require aligned pointers. This means that any code using structs with unaligned fields in pin-init is unsound. By default, the `init!` macro generates references to initialized fields, which makes the compiler check that those fields are aligned. However, we added the `#[disable_initialized_field_access]` attribute to avoid this behavior in 71988db ("internal: init: add escape hatch for referencing initialized fields"). Thus remove the `#[disable_initialized_field_access]` attribute from `init!`, which is the only safe way to create an initializer handling unaligned fields. If support for in-place initializing structs with unaligned fields is required in the future, we could figure out a solution. This is tracked in [2]. Reported-by: Gary Guo <gary@garyguo.net> Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1] Link: #112 [2] Fixes: 71988db ("internal: init: add escape hatch for referencing initialized fields") Signed-off-by: Benno Lossin <lossin@kernel.org>

The functions `[Pin]Init::__[pinned_]init` and `ptr::write` called from the `init!` macro require the passed pointer to be aligned. This fact is ensured by the creation of field accessors to previously initialized fields. Since we missed this very important fact from the beginning [1], document it in the code. Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1] Signed-off-by: Benno Lossin <lossin@kernel.org>

BennoLossin · 2026-02-27T19:25:31Z

Gary noticed [1] that the initializer macros as well as the [Pin]Init traits cannot support packed struct, since they use operations that require aligned pointers. This means that any code using packed structs and pin-init is unsound.

Thus remove the #[disable_initialized_field_access] attribute from init!, which is the only safe way to create an initializer of a packed struct.

In the future, we can add support for packed structs by changing the trait infrastructure to include UnalignedInit or hopefully another mechanism.

Reported-by: Gary Guo gary@garyguo.net
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1]
Fixes: db96c51 ("add references to previously initialized fields")

nbdd0121 · 2026-02-27T22:25:35Z

The commit that this fixes should be the one that introduced this feature instead? Arguably creating reference is the fix, not the fixed commit.

BennoLossin · 2026-02-28T08:30:05Z

Yeah you're right, fixed it. Both my kernel tests & the intel kernel CI also reported no issues, so I'll send this to the list as well.

Gary noticed [1] that the initializer macros as well as the `[Pin]Init` traits cannot support unaligned fields, since they use operations that require aligned pointers. This means that any code using structs with unaligned fields in pin-init is unsound. By default, the `init!` macro generates references to initialized fields, which makes the compiler check that those fields are aligned. However, we added the `#[disable_initialized_field_access]` attribute to avoid this behavior in 71988db ("internal: init: add escape hatch for referencing initialized fields"). Thus remove the `#[disable_initialized_field_access]` attribute from `init!`, which is the only safe way to create an initializer handling unaligned fields. If support for in-place initializing structs with unaligned fields is required in the future, we could figure out a solution. This is tracked in [2]. Reported-by: Gary Guo <gary@garyguo.net> Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1] Link: #112 [2] Fixes: 71988db ("internal: init: add escape hatch for referencing initialized fields") Signed-off-by: Benno Lossin <lossin@kernel.org>

The functions `[Pin]Init::__[pinned_]init` and `ptr::write` called from the `init!` macro require the passed pointer to be aligned. This fact is ensured by the creation of field accessors to previously initialized fields. Since we missed this very important fact from the beginning [1], document it in the code. Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1] Signed-off-by: Benno Lossin <lossin@kernel.org>

BennoLossin · 2026-02-27T19:25:31Z

Gary noticed [1] that the initializer macros as well as the [Pin]Init traits cannot support packed struct, since they use operations that require aligned pointers. This means that any code using packed structs and pin-init is unsound.

Thus remove the #[disable_initialized_field_access] attribute from init!, which is the only safe way to create an initializer of a packed struct.

In the future, we can add support for packed structs by changing the trait infrastructure to include UnalignedInit or hopefully another mechanism.

Reported-by: Gary Guo gary@garyguo.net
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1]
Fixes: db96c51 ("add references to previously initialized fields")

nbdd0121 · 2026-02-27T22:25:35Z

The commit that this fixes should be the one that introduced this feature instead? Arguably creating reference is the fix, not the fixed commit.

BennoLossin · 2026-02-28T08:30:05Z

Yeah you're right, fixed it. Both my kernel tests & the intel kernel CI also reported no issues, so I'll send this to the list as well.

Gary noticed [1] that the initializer macros as well as the `[Pin]Init` traits cannot support unaligned fields, since they use operations that require aligned pointers. This means that any code using structs with unaligned fields in pin-init is unsound. By default, the `init!` macro generates references to initialized fields, which makes the compiler check that those fields are aligned. However, we added the `#[disable_initialized_field_access]` attribute to avoid this behavior in 71988db ("internal: init: add escape hatch for referencing initialized fields"). Thus remove the `#[disable_initialized_field_access]` attribute from `init!`, which is the only safe way to create an initializer handling unaligned fields. If support for in-place initializing structs with unaligned fields is required in the future, we could figure out a solution. This is tracked in [2]. Reported-by: Gary Guo <gary@garyguo.net> Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1] Link: #112 [2] Fixes: 71988db ("internal: init: add escape hatch for referencing initialized fields") Signed-off-by: Benno Lossin <lossin@kernel.org>

The functions `[Pin]Init::__[pinned_]init` and `ptr::write` called from the `init!` macro require the passed pointer to be aligned. This fact is ensured by the creation of field accessors to previously initialized fields. Since we missed this very important fact from the beginning [1], document it in the code. Link: https://rust-for-linux.zulipchat.com/#narrow/channel/561532-pin-init/topic/initialized.20field.20accessor.20detection/with/576210658 [1] Signed-off-by: Benno Lossin <lossin@kernel.org>

BennoLossin requested a review from nbdd0121 February 27, 2026 19:25

BennoLossin force-pushed the dev/unsound-fix-packed branch from a4f72d5 to a00f29bCompare February 28, 2026 08:22

BennoLossin force-pushed the dev/unsound-fix-packed branch from a00f29b to 54fd39fCompare February 28, 2026 08:38

BennoLossin mentioned this pull request Feb 28, 2026
Unaligned Fields Support #112
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BennoLossin force-pushed the dev/unsound-fix-packed branch 3 times, most recently from 2f6d697 to 14ea16fCompare March 2, 2026 13:47

BennoLossin added 2 commits March 9, 2026 07:51

BennoLossin force-pushed the dev/unsound-fix-packed branch from 14ea16f to ef5a2daCompare March 9, 2026 06:51

BennoLossin mentioned this pull request Mar 9, 2026
internal: init: implement automated field usage scanning #106
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nbdd0121 approved these changes Mar 9, 2026
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BennoLossin mentioned this pull request Mar 10, 2026
Only create accessors for initialized fields if it would be used #98
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BennoLossin merged commit b4c9632 into mainMar 14, 2026
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BennoLossin deleted the dev/unsound-fix-packed branch March 14, 2026 20:46