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Auto merge of #3848 - felix91gr:null_transmute, r=flip1995
Transmuting known null ptr to ref Working on implementing #628
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,112 @@ | ||
| use crate::consts::{constant_context, Constant}; | ||
| use crate::utils::{match_qpath, span_lint}; | ||
| use if_chain::if_chain; | ||
| use rustc::hir::{Expr, ExprKind}; | ||
| use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintContext, LintPass}; | ||
| use rustc::{declare_tool_lint, lint_array}; | ||
| use syntax::ast::LitKind; | ||
|
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||
| declare_clippy_lint! { | ||
| /// **What it does:** Checks for transmute calls which would receive a null pointer. | ||
| /// | ||
| /// **Why is this bad?** Transmuting a null pointer is undefined behavior. | ||
| /// | ||
| /// **Known problems:** Not all cases can be detected at the moment of this writing. | ||
| /// For example, variables which hold a null pointer and are then fed to a `transmute` | ||
| /// call, aren't detectable yet. | ||
| /// | ||
| /// **Example:** | ||
| /// ```rust | ||
| /// let null_ref: &u64 = unsafe { std::mem::transmute(0 as *const u64) }; | ||
| /// ``` | ||
| pub TRANSMUTING_NULL, | ||
| correctness, | ||
| "transmutes from a null pointer to a reference, which is undefined behavior" | ||
| } | ||
|
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||
| #[derive(Copy, Clone)] | ||
| pub struct Pass; | ||
|
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| impl LintPass for Pass { | ||
| fn get_lints(&self) -> LintArray { | ||
| lint_array!(TRANSMUTING_NULL,) | ||
| } | ||
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| fn name(&self) -> &'static str { | ||
| "TransmutingNull" | ||
| } | ||
| } | ||
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| const LINT_MSG: &str = "transmuting a known null pointer into a reference."; | ||
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| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass { | ||
| fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) { | ||
| if in_external_macro(cx.sess(), expr.span) { | ||
| return; | ||
| } | ||
|
|
||
| if_chain! { | ||
| if let ExprKind::Call(ref func, ref args) = expr.node; | ||
| if let ExprKind::Path(ref path) = func.node; | ||
| if match_qpath(path, &["std", "mem", "transmute"]); | ||
| if args.len() == 1; | ||
|
|
||
| then { | ||
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| // Catching transmute over constants that resolve to `null`. | ||
| let mut const_eval_context = constant_context(cx, cx.tables); | ||
| if_chain! { | ||
| if let ExprKind::Path(ref _qpath) = args[0].node; | ||
| let x = const_eval_context.expr(&args[0]); | ||
| if let Some(constant) = x; | ||
| if let Constant::RawPtr(ptr_value) = constant; | ||
| if ptr_value == 0; | ||
| then { | ||
| span_lint( | ||
| cx, | ||
| TRANSMUTING_NULL, | ||
| expr.span, | ||
| LINT_MSG) | ||
| } | ||
| } | ||
|
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||
| // Catching: | ||
| // `std::mem::transmute(0 as *const i32)` | ||
| if_chain! { | ||
| if let ExprKind::Cast(ref inner_expr, ref _cast_ty) = args[0].node; | ||
| if let ExprKind::Lit(ref lit) = inner_expr.node; | ||
| if let LitKind::Int(0, _) = lit.node; | ||
| then { | ||
| span_lint( | ||
| cx, | ||
| TRANSMUTING_NULL, | ||
| expr.span, | ||
| LINT_MSG) | ||
| } | ||
| } | ||
|
|
||
| // Catching: | ||
| // `std::mem::transmute(std::ptr::null::<i32>())` | ||
| if_chain! { | ||
| if let ExprKind::Call(ref func1, ref args1) = args[0].node; | ||
| if let ExprKind::Path(ref path1) = func1.node; | ||
| if match_qpath(path1, &["std", "ptr", "null"]); | ||
| if args1.len() == 0; | ||
| then { | ||
| span_lint( | ||
| cx, | ||
| TRANSMUTING_NULL, | ||
| expr.span, | ||
| LINT_MSG) | ||
| } | ||
| } | ||
|
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||
| // FIXME: | ||
| // Also catch transmutations of variables which are known nulls. | ||
| // To do this, MIR const propagation seems to be the better tool. | ||
| // Whenever MIR const prop routines are more developed, this will | ||
| // become available. As of this writing (25/03/19) it is not yet. | ||
| } | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,30 @@ | ||
| #![allow(dead_code)] | ||
| #![warn(clippy::transmuting_null)] | ||
| #![allow(clippy::zero_ptr)] | ||
| #![allow(clippy::transmute_ptr_to_ref)] | ||
| #![allow(clippy::eq_op)] | ||
|
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| // Easy to lint because these only span one line. | ||
| fn one_liners() { | ||
| unsafe { | ||
| let _: &u64 = std::mem::transmute(0 as *const u64); | ||
| let _: &u64 = std::mem::transmute(std::ptr::null::<u64>()); | ||
| } | ||
| } | ||
|
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| pub const ZPTR: *const usize = 0 as *const _; | ||
| pub const NOT_ZPTR: *const usize = 1 as *const _; | ||
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| fn transmute_const() { | ||
| unsafe { | ||
| // Should raise a lint. | ||
| let _: &u64 = std::mem::transmute(ZPTR); | ||
| // Should NOT raise a lint. | ||
| let _: &u64 = std::mem::transmute(NOT_ZPTR); | ||
| } | ||
| } | ||
|
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||
| fn main() { | ||
| one_liners(); | ||
| transmute_const(); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,22 @@ | ||
| error: transmuting a known null pointer into a reference. | ||
| --> $DIR/transmuting_null.rs:10:23 | ||
| | | ||
| LL | let _: &u64 = std::mem::transmute(0 as *const u64); | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| | | ||
| = note: `-D clippy::transmuting-null` implied by `-D warnings` | ||
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| error: transmuting a known null pointer into a reference. | ||
| --> $DIR/transmuting_null.rs:11:23 | ||
| | | ||
| LL | let _: &u64 = std::mem::transmute(std::ptr::null::<u64>()); | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
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| error: transmuting a known null pointer into a reference. | ||
| --> $DIR/transmuting_null.rs:21:23 | ||
| | | ||
| LL | let _: &u64 = std::mem::transmute(ZPTR); | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
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| error: aborting due to 3 previous errors | ||
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