forked from torvalds/linux
-
Notifications
You must be signed in to change notification settings - Fork 423
New issue
Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.
By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.
Already on GitHub? Sign in to your account
Patch/pinned init v4 #991
Closed
Closed
Patch/pinned init v4 #991
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Closed
Darksonn
reviewed
Mar 31, 2023
Darksonn
reviewed
Mar 31, 2023
y86-dev
force-pushed
the
patch/pinned-init-v4
branch
2 times, most recently
from
March 31, 2023 16:09
a965a4e
to
66121f2
Compare
This feature enables the use of the `pin!` macro for the `stack_pin_init!` macro. This feature is already stabilized in Rust version 1.68. Signed-off-by: Benno Lossin <[email protected]> Cc: Gary Guo <[email protected]> Cc: Andreas Hindborg <[email protected]> Cc: Alice Ryhl <[email protected]>
Add the `quote!` macro for creating `TokenStream`s directly via the given Rust tokens. It also supports repetitions using iterators. It will be used by the pin-init API proc-macros to generate code. Signed-off-by: Gary Guo <[email protected]> Signed-off-by: Benno Lossin <[email protected]> Cc: Alice Ryhl <[email protected]> Cc: Andreas Hindborg <[email protected]>
Change the error type of the constructors of `Arc` and `UniqueArc` to be `AllocError` instead of `Error`. This makes the API more clear as to what can go wrong when calling `try_new` or its variants. Signed-off-by: Benno Lossin <[email protected]> Cc: Gary Guo <[email protected]> Cc: Andreas Hindborg <[email protected]> Cc: Alice Ryhl <[email protected]>
Adds the `assume_init` function to `UniqueArc<MaybeUninit<T>>` that unsafely assumes the value to be initialized and yields a value of type `UniqueArc<T>`. This function is used when manually initializing the pointee of an `UniqueArc`. Signed-off-by: Benno Lossin <[email protected]> Reviewed-by: Wedson Almeida Filho <[email protected]> Reviewed-by: Andreas Hindborg <[email protected]> Reviewed-by: Alice Ryhl <[email protected]>
This function mirrors `UnsafeCell::raw_get`. It avoids creating a reference and allows solely using raw pointers. The `pin-init` API will be using this, since uninitialized memory requires raw pointers. Signed-off-by: Benno Lossin <[email protected]> Reviewed-by: Gary Guo <[email protected]> Reviewed-by: Andreas Hindborg <[email protected]> Reviewed-by: Alice Ryhl <[email protected]>
This API is used to facilitate safe pinned initialization of structs. It replaces cumbersome `unsafe` manual initialization with elegant safe macro invocations. Due to the size of this change it has been split into six commits: 1. This commit introducing the basic public interface: traits and functions to represent and create initializers. 2. Adds the `#[pin_data]`, `pin_init!`, `try_pin_init!`, `init!` and `try_init!` macros along with their internal types. 3. Adds the `InPlaceInit` trait that allows using an initializer to create an object inside of a `Box<T>` and other smart pointers. 4. Adds the `PinnedDrop` trait and adds macro support for it in the `#[pin_data]` macro. 5. Adds the `stack_pin_init!` macro allowing to pin-initialize a struct on the stack. 6. Adds the `Zeroable` trait and `init::zeroed` function to initialize types that have `0x00` in all bytes as a valid bit pattern. -- In this section the problem that the new pin-init API solves is outlined. This message describes the entirety of the API, not just the parts introduced in this commit. For a more granular explanation and additional information on pinning and this issue, view [1]. Pinning is Rust's way of enforcing the address stability of a value. When a value gets pinned it will be impossible for safe code to move it to another location. This is done by wrapping pointers to said object with `Pin<P>`. This wrapper prevents safe code from creating mutable references to the object, preventing mutable access, which is needed to move the value. `Pin<P>` provides `unsafe` functions to circumvent this and allow modifications regardless. It is then the programmer's responsibility to uphold the pinning guarantee. Many kernel data structures require a stable address, because there are foreign pointers to them which would get invalidated by moving the structure. Since these data structures are usually embedded in structs to use them, this pinning property propagates to the container struct. Resulting in most structs in both Rust and C code needing to be pinned. So if we want to have a `mutex` field in a Rust struct, this struct also needs to be pinned, because a `mutex` contains a `list_head`. Additionally initializing a `list_head` requires already having the final memory location available, because it is initialized by pointing it to itself. But this presents another challenge in Rust: values have to be initialized at all times. There is the `MaybeUninit<T>` wrapper type, which allows handling uninitialized memory, but this requires using the `unsafe` raw pointers and a casting the type to the initialized variant. This problem gets exacerbated when considering encapsulation and the normal safety requirements of Rust code. The fields of the Rust `Mutex<T>` should not be accessible to normal driver code. After all if anyone can modify the fields, there is no way to ensure the invariants of the `Mutex<T>` are upheld. But if the fields are inaccessible, then initialization of a `Mutex<T>` needs to be somehow achieved via a function or a macro. Because the `Mutex<T>` must be pinned in memory, the function cannot return it by value. It also cannot allocate a `Box` to put the `Mutex<T>` into, because that is an unnecessary allocation and indirection which would hurt performance. The current solution was to split this function into two parts: 1. A `new` function that returns a partially initialized `Mutex<T>`, 2. An `init` function that requires the `Mutex<T>` to be pinned and that fully initializes the `Mutex<T>`. Both of these functions have to be marked `unsafe`, since a call to `new` needs to be accompanied with a call to `init`, otherwise using the `Mutex<T>` could result in UB. And because calling `init` twice also is not safe. While `Mutex<T>` initialization cannot fail, other structs might also have to allocate memory, which would result in conditional successful initialization requiring even more manual accommodation work. Combine this with the problem of pin-projections -- the way of accessing fields of a pinned struct -- which also have an `unsafe` API, pinned initialization is riddled with `unsafe` resulting in very poor ergonomics. Not only that, but also having to call two functions possibly multiple lines apart makes it very easy to forget it outright or during refactoring. Here is an example of the current way of initializing a struct with two synchronization primitives (see [2] for the full example): struct SharedState { state_changed: CondVar, inner: Mutex<SharedStateInner>, } impl SharedState { fn try_new() -> Result<Arc<Self>> { let mut state = Pin::from(UniqueArc::try_new(Self { // SAFETY: `condvar_init!` is called below. state_changed: unsafe { CondVar::new() }, // SAFETY: `mutex_init!` is called below. inner: unsafe { Mutex::new(SharedStateInner { token_count: 0 }) }, })?); // SAFETY: `state_changed` is pinned when `state` is. let pinned = unsafe { state.as_mut().map_unchecked_mut(|s| &mut s.state_changed) }; kernel::condvar_init!(pinned, "SharedState::state_changed"); // SAFETY: `inner` is pinned when `state` is. let pinned = unsafe { state.as_mut().map_unchecked_mut(|s| &mut s.inner) }; kernel::mutex_init!(pinned, "SharedState::inner"); Ok(state.into()) } } The pin-init API of this patch solves this issue by providing a comprehensive solution comprised of macros and traits. Here is the example from above using the pin-init API: #[pin_data] struct SharedState { #[pin] state_changed: CondVar, #[pin] inner: Mutex<SharedStateInner>, } impl SharedState { fn new() -> impl PinInit<Self> { pin_init!(Self { state_changed <- new_condvar!("SharedState::state_changed"), inner <- new_mutex!( SharedStateInner { token_count: 0 }, "SharedState::inner", ), }) } } Notably the way the macro is used here requires no `unsafe` and thus comes with the usual Rust promise of safe code not introducing any memory violations. Additionally it is now up to the caller of `new()` to decide the memory location of the `SharedState`. They can choose at the moment `Arc<T>`, `Box<T>` or the stack. -- The API has the following architecture: 1. Initializer traits `PinInit<T, E>` and `Init<T, E>` that act like closures. 2. Macros to create these initializer traits safely. 3. Functions to allow manually writing initializers. The initializers (an `impl PinInit<T, E>`) receive a raw pointer pointing to uninitialized memory and their job is to fully initialize a `T` at that location. If initialization fails, they return an error (`E`) by value. This way of initializing cannot be safely exposed to the user, since it relies upon these properties outside of the control of the trait: - the memory location (slot) needs to be valid memory, - if initialization fails, the slot should not be read from, - the value in the slot should be pinned, so it cannot move and the memory cannot be deallocated until the value is dropped. This is why using an initializer is facilitated by another trait that ensures these requirements. These initializers can be created manually by just supplying a closure that fulfills the same safety requirements as `PinInit<T, E>`. But this is an `unsafe` operation. To allow safe initializer creation, the `pin_init!` is provided along with three other variants: `try_pin_init!`, `try_init!` and `init!`. These take a modified struct initializer as a parameter and generate a closure that initializes the fields in sequence. The macros take great care in upholding the safety requirements: - A shadowed struct type is used as the return type of the closure instead of `()`. This is to prevent early returns, as these would prevent full initialization. - To ensure every field is only initialized once, a normal struct initializer is placed in unreachable code. The type checker will emit errors if a field is missing or specified multiple times. - When initializing a field fails, the whole initializer will fail and automatically drop fields that have been initialized earlier. - Only the correct initializer type is allowed for unpinned fields. You cannot use a `impl PinInit<T, E>` to initialize a structurally not pinned field. To ensure the last point, an additional macro `#[pin_data]` is needed. This macro annotates the struct itself and the user specifies structurally pinned and not pinned fields. Because dropping a pinned struct is also not allowed to break the pinning invariants, another macro attribute `#[pinned_drop]` is needed. This macro is introduced in a following commit. These two macros also have mechanisms to ensure the overall safety of the API. Additionally, they utilize a combined proc-macro, declarative macro design: first a proc-macro enables the outer attribute syntax `#[...]` and does some important pre-parsing. Notably this prepares the generics such that the declarative macro can handle them using token trees. Then the actual parsing of the structure and the emission of code is handled by a declarative macro. For pin-projections the crates `pin-project` [3] and `pin-project-lite` [4] had been considered, but were ultimately rejected: - `pin-project` depends on `syn` [5] which is a very big dependency, around 50k lines of code. - `pin-project-lite` is a more reasonable 5k lines of code, but contains a very complex declarative macro to parse generics. On top of that it would require modification that would need to be maintained independently. Link: https://rust-for-linux.com/the-safe-pinned-initialization-problem [1] Link: https://github.com/Rust-for-Linux/linux/blob/f509ede33fc10a07eba3da14aa00302bd4b5dddd/samples/rust/rust_miscdev.rs [2] Link: https://crates.io/crates/pin-project [3] Link: https://crates.io/crates/pin-project-lite [4] Link: https://crates.io/crates/syn [5] Co-developed-by: Gary Guo <[email protected]> Signed-off-by: Gary Guo <[email protected]> Signed-off-by: Benno Lossin <[email protected]> Cc: Andreas Hindborg <[email protected]> Cc: Alice Ryhl <[email protected]>
Add the following initializer macros: - `#[pin_data]` to annotate structurally pinned fields of structs, needed for `pin_init!` and `try_pin_init!` to select the correct initializer of fields. - `pin_init!` create a pin-initializer for a struct with the `Infallible` error type. - `try_pin_init!` create a pin-initializer for a struct with a custom error type (`kernel::error::Error` is the default). - `init!` create an in-place-initializer for a struct with the `Infallible` error type. - `try_init!` create an in-place-initializer for a struct with a custom error type (`kernel::error::Error` is the default). Also add their needed internal helper traits and structs. Co-developed-by: Gary Guo <[email protected]> Signed-off-by: Gary Guo <[email protected]> Signed-off-by: Benno Lossin <[email protected]> Cc: Alice Ryhl <[email protected]> Cc: Andreas Hindborg <[email protected]>
…ters The `InPlaceInit` trait that provides two functions, for initializing using `PinInit<T, E>` and `Init<T>`. It is implemented by `Arc<T>`, `UniqueArc<T>` and `Box<T>`. Signed-off-by: Benno Lossin <[email protected]> Cc: Andreas Hindborg <[email protected]> Cc: Alice Ryhl <[email protected]> Cc: Gary Guo <[email protected]>
The `PinnedDrop` trait that facilitates destruction of pinned types. It has to be implemented via the `#[pinned_drop]` macro, since the `drop` function should not be called by normal code, only by other destructors. It also only works on structs that are annotated with `#[pin_data(PinnedDrop)]`. Co-developed-by: Gary Guo <[email protected]> Signed-off-by: Gary Guo <[email protected]> Signed-off-by: Benno Lossin <[email protected]> Cc: Alice Ryhl <[email protected]> Cc: Andreas Hindborg <[email protected]>
The `stack_pin_init!` macro allows pin-initializing a value on the stack. It accepts a `impl PinInit<T, E>` to initialize a `T`. It allows propagating any errors via `?` or handling it normally via `match`. Signed-off-by: Benno Lossin <[email protected]> Cc: Alice Ryhl <[email protected]> Cc: Andreas Hindborg <[email protected]> Cc: Gary Guo <[email protected]>
Add the `Zeroable` trait which marks types that can be initialized by writing `0x00` to every byte of the type. Also add the `init::zeroed` function that creates an initializer for a `Zeroable` type that writes `0x00` to every byte. Signed-off-by: Benno Lossin <[email protected]> Cc: Gary Guo <[email protected]> Cc: Alice Ryhl <[email protected]> Cc: Andreas Hindborg <[email protected]>
Add `pin-init` API macros and traits to the prelude. Signed-off-by: Benno Lossin <[email protected]> Reviewed-by: Gary Guo <[email protected]> Reviewed-by: Alice Ryhl <[email protected]> Reviewed-by: Andreas Hindborg <[email protected]>
Add helper functions to more easily initialize `Opaque<T>` via FFI and rust raw initializer functions. These functions take a function pointer to the FFI/raw initialization function and take between 0-4 other arguments. It then returns an initializer that uses the FFI/raw initialization function along with the given arguments to initialize an `Opaque<T>`. Signed-off-by: Benno Lossin <[email protected]> Reviewed-by: Alice Ryhl <[email protected]> Reviewed-by: Andreas Hindborg <[email protected]> Cc: Gary Guo <[email protected]>
`UniqueArc::try_new_uninit` calls `Arc::try_new(MaybeUninit::uninit())`. This results in the uninitialized memory being placed on the stack, which may be arbitrarily large due to the generic `T` and thus could cause a stack overflow for large types. Change the implementation to use the pin-init API which enables in-place initialization. In particular it avoids having to first construct and then move the uninitialized memory from the stack into the final location. Signed-off-by: Benno Lossin <[email protected]> Cc: Gary Guo <[email protected]> Cc: Alice Ryhl <[email protected]> Cc: Andreas Hindborg <[email protected]>
Add two functions `init_with` and `pin_init_with` to `UniqueArc<MaybeUninit<T>>` to initialize the memory of already allocated `UniqueArc`s. This is useful when you want to allocate memory check some condition inside of a context where allocation is forbidden and then conditionally initialize an object. Signed-off-by: Benno Lossin <[email protected]> Reviewed-by: Gary Guo <[email protected]> Reviewed-by: Alice Ryhl <[email protected]> Reviewed-by: Andreas Hindborg <[email protected]>
y86-dev
force-pushed
the
patch/pinned-init-v4
branch
from
March 31, 2023 21:27
66121f2
to
fd7296f
Compare
continued at #992 |
ojeda
pushed a commit
that referenced
this pull request
Oct 7, 2024
After commit 7c6d2ec ("net: be more gentle about silly gso requests coming from user") virtio_net_hdr_to_skb() had sanity check to detect malicious attempts from user space to cook a bad GSO packet. Then commit cf9acc9 ("net: virtio_net_hdr_to_skb: count transport header in UFO") while fixing one issue, allowed user space to cook a GSO packet with the following characteristic : IPv4 SKB_GSO_UDP, gso_size=3, skb->len = 28. When this packet arrives in qdisc_pkt_len_init(), we end up with hdr_len = 28 (IPv4 header + UDP header), matching skb->len Then the following sets gso_segs to 0 : gso_segs = DIV_ROUND_UP(skb->len - hdr_len, shinfo->gso_size); Then later we set qdisc_skb_cb(skb)->pkt_len to back to zero :/ qdisc_skb_cb(skb)->pkt_len += (gso_segs - 1) * hdr_len; This leads to the following crash in fq_codel [1] qdisc_pkt_len_init() is best effort, we only want an estimation of the bytes sent on the wire, not crashing the kernel. This patch is fixing this particular issue, a following one adds more sanity checks for another potential bug. [1] [ 70.724101] BUG: kernel NULL pointer dereference, address: 0000000000000000 [ 70.724561] #PF: supervisor read access in kernel mode [ 70.724561] #PF: error_code(0x0000) - not-present page [ 70.724561] PGD 10ac61067 P4D 10ac61067 PUD 107ee2067 PMD 0 [ 70.724561] Oops: Oops: 0000 [#1] SMP NOPTI [ 70.724561] CPU: 11 UID: 0 PID: 2163 Comm: b358537762 Not tainted 6.11.0-virtme #991 [ 70.724561] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 70.724561] RIP: 0010:fq_codel_enqueue (net/sched/sch_fq_codel.c:120 net/sched/sch_fq_codel.c:168 net/sched/sch_fq_codel.c:230) sch_fq_codel [ 70.724561] Code: 24 08 49 c1 e1 06 44 89 7c 24 18 45 31 ed 45 31 c0 31 ff 89 44 24 14 4c 03 8b 90 01 00 00 eb 04 39 ca 73 37 4d 8b 39 83 c7 01 <49> 8b 17 49 89 11 41 8b 57 28 45 8b 5f 34 49 c7 07 00 00 00 00 49 All code ======== 0: 24 08 and $0x8,%al 2: 49 c1 e1 06 shl $0x6,%r9 6: 44 89 7c 24 18 mov %r15d,0x18(%rsp) b: 45 31 ed xor %r13d,%r13d e: 45 31 c0 xor %r8d,%r8d 11: 31 ff xor %edi,%edi 13: 89 44 24 14 mov %eax,0x14(%rsp) 17: 4c 03 8b 90 01 00 00 add 0x190(%rbx),%r9 1e: eb 04 jmp 0x24 20: 39 ca cmp %ecx,%edx 22: 73 37 jae 0x5b 24: 4d 8b 39 mov (%r9),%r15 27: 83 c7 01 add $0x1,%edi 2a:* 49 8b 17 mov (%r15),%rdx <-- trapping instruction 2d: 49 89 11 mov %rdx,(%r9) 30: 41 8b 57 28 mov 0x28(%r15),%edx 34: 45 8b 5f 34 mov 0x34(%r15),%r11d 38: 49 c7 07 00 00 00 00 movq $0x0,(%r15) 3f: 49 rex.WB Code starting with the faulting instruction =========================================== 0: 49 8b 17 mov (%r15),%rdx 3: 49 89 11 mov %rdx,(%r9) 6: 41 8b 57 28 mov 0x28(%r15),%edx a: 45 8b 5f 34 mov 0x34(%r15),%r11d e: 49 c7 07 00 00 00 00 movq $0x0,(%r15) 15: 49 rex.WB [ 70.724561] RSP: 0018:ffff95ae85e6fb90 EFLAGS: 00000202 [ 70.724561] RAX: 0000000002000000 RBX: ffff95ae841de000 RCX: 0000000000000000 [ 70.724561] RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001 [ 70.724561] RBP: ffff95ae85e6fbf8 R08: 0000000000000000 R09: ffff95b710a30000 [ 70.724561] R10: 0000000000000000 R11: bdf289445ce31881 R12: ffff95ae85e6fc58 [ 70.724561] R13: 0000000000000000 R14: 0000000000000040 R15: 0000000000000000 [ 70.724561] FS: 000000002c5c1380(0000) GS:ffff95bd7fcc0000(0000) knlGS:0000000000000000 [ 70.724561] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 70.724561] CR2: 0000000000000000 CR3: 000000010c568000 CR4: 00000000000006f0 [ 70.724561] Call Trace: [ 70.724561] <TASK> [ 70.724561] ? __die (arch/x86/kernel/dumpstack.c:421 arch/x86/kernel/dumpstack.c:434) [ 70.724561] ? page_fault_oops (arch/x86/mm/fault.c:715) [ 70.724561] ? exc_page_fault (./arch/x86/include/asm/irqflags.h:26 ./arch/x86/include/asm/irqflags.h:87 ./arch/x86/include/asm/irqflags.h:147 arch/x86/mm/fault.c:1489 arch/x86/mm/fault.c:1539) [ 70.724561] ? asm_exc_page_fault (./arch/x86/include/asm/idtentry.h:623) [ 70.724561] ? fq_codel_enqueue (net/sched/sch_fq_codel.c:120 net/sched/sch_fq_codel.c:168 net/sched/sch_fq_codel.c:230) sch_fq_codel [ 70.724561] dev_qdisc_enqueue (net/core/dev.c:3784) [ 70.724561] __dev_queue_xmit (net/core/dev.c:3880 (discriminator 2) net/core/dev.c:4390 (discriminator 2)) [ 70.724561] ? irqentry_enter (kernel/entry/common.c:237) [ 70.724561] ? sysvec_apic_timer_interrupt (./arch/x86/include/asm/hardirq.h:74 (discriminator 2) arch/x86/kernel/apic/apic.c:1043 (discriminator 2) arch/x86/kernel/apic/apic.c:1043 (discriminator 2)) [ 70.724561] ? trace_hardirqs_on (kernel/trace/trace_preemptirq.c:58 (discriminator 4)) [ 70.724561] ? asm_sysvec_apic_timer_interrupt (./arch/x86/include/asm/idtentry.h:702) [ 70.724561] ? virtio_net_hdr_to_skb.constprop.0 (./include/linux/virtio_net.h:129 (discriminator 1)) [ 70.724561] packet_sendmsg (net/packet/af_packet.c:3145 (discriminator 1) net/packet/af_packet.c:3177 (discriminator 1)) [ 70.724561] ? _raw_spin_lock_bh (./arch/x86/include/asm/atomic.h:107 (discriminator 4) ./include/linux/atomic/atomic-arch-fallback.h:2170 (discriminator 4) ./include/linux/atomic/atomic-instrumented.h:1302 (discriminator 4) ./include/asm-generic/qspinlock.h:111 (discriminator 4) ./include/linux/spinlock.h:187 (discriminator 4) ./include/linux/spinlock_api_smp.h:127 (discriminator 4) kernel/locking/spinlock.c:178 (discriminator 4)) [ 70.724561] ? netdev_name_node_lookup_rcu (net/core/dev.c:325 (discriminator 1)) [ 70.724561] __sys_sendto (net/socket.c:730 (discriminator 1) net/socket.c:745 (discriminator 1) net/socket.c:2210 (discriminator 1)) [ 70.724561] ? __sys_setsockopt (./include/linux/file.h:34 net/socket.c:2355) [ 70.724561] __x64_sys_sendto (net/socket.c:2222 (discriminator 1) net/socket.c:2218 (discriminator 1) net/socket.c:2218 (discriminator 1)) [ 70.724561] do_syscall_64 (arch/x86/entry/common.c:52 (discriminator 1) arch/x86/entry/common.c:83 (discriminator 1)) [ 70.724561] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) [ 70.724561] RIP: 0033:0x41ae09 Fixes: cf9acc9 ("net: virtio_net_hdr_to_skb: count transport header in UFO") Reported-by: syzbot <[email protected]> Signed-off-by: Eric Dumazet <[email protected]> Cc: Jonathan Davies <[email protected]> Reviewed-by: Willem de Bruijn <[email protected]> Reviewed-by: Jonathan Davies <[email protected]> Reviewed-by: David Ahern <[email protected]> Signed-off-by: Paolo Abeni <[email protected]>
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
No description provided.