39 lines
1.2 KiB
Plaintext
39 lines
1.2 KiB
Plaintext
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== Why is this an issue?
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When casting a raw pointer to a slice, the produced raw pointer does not correctly update its length metadata, leading to potential issues such as creating a slice with less data than intended or more data, risking undefined behavior upon dereferencing.
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== How to fix it
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Use `ptr::slice_from_raw_parts` to construct a slice from a data pointer and the correct length.
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=== Code examples
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==== Noncompliant code example
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[source,rust,diff-id=1,diff-type=noncompliant]
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----
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let a = [1_u8, 2, 3, 4];
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let p = &a as *const [u8] as *const [u32];
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unsafe {
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println!("{:?}", &*p); // Noncompliant: Undefined behavior
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}
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----
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==== Compliant solution
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[source,rust,diff-id=1,diff-type=compliant]
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----
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let a = [1_i32, 2, 3, 4];
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let old_ptr = &a as *const [i32];
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// The data pointer is cast to a pointer to the target `u8` not `[u8]`
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// The length comes from the known length of 4 i32s times the 4 bytes per i32
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let new_ptr = core::ptr::slice_from_raw_parts(old_ptr as *const u8, 16);
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unsafe {
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println!("{:?}", &*new_ptr);
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}
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----
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== Resources
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=== Documentation
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* Clippy Lints - https://rust-lang.github.io/rust-clippy/master/index.html#cast_slice_different_sizes
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