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Orphaned memory buffer detector

License

Apache-2.0, MIT licenses found

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Apache-2.0
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ehsanmok/smartalloc-rs

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Buildno stdcrates.iodocs.rs

This crate provides ano_std idiomatic Rust binding tosmartalloc used fordetecting orphaned buffer allocation which is a type of heap memory leak that the program has lost all access to it.The primary usecase is as adebugging tool when writingunsafe code where normal Rust static checks are not available.It is best used along sideSANs where SANsalone are either unable to detect or their outputs are cumbersome to work through.To get the best experience,RUSTFLAGS=-Zsanitizer=leak is used and is included in.cargo/config.toml.

Usage

[dev-dependencies]smartalloc ="0.2"

In fact, with#![cfg(debug_assertions)] the crate doesnot compile in the--release mode so preventing from any accidental usage.The craterequires nightly Rust toolchain (MSRV 1.65).

Example

During debugging, configure theSmartAlloc as the global allocator. Then includesm_dump(true) at the end of an unsafe code block.Here is theexamples/orphan.rs

use core::alloc::{GlobalAlloc,Layout};use smartalloc::{sm_dump,SmartAlloc};#[global_allocator]staticGLOBAL:SmartAlloc =SmartAlloc;fnmain(){unsafe{let alloc =SmartAlloc;let layout =Layout::from_size_align(8,8).unwrap();        alloc.alloc(layout);// orphaned memory leak as it's pointer is lost// and there's no alloc.dealloc(ptr, layout)sm_dump(true);}}

which outputs

Orphaned buffer:       8 bytes allocated at line 12 of examples/orphan.rs

Note that the detector throws

Orphaned buffer:       5 bytes allocated at line 5 of examples/orphan.rsOrphaned buffer:      48 bytes allocated at line 5 of examples/orphan.rs

which refers to the#[global_allocator] itself and can be ignored.

Features

The detector can be turned off usingsm_static(true) and turned back onsm_static(false) to wrap cases where allocation is done through std or safe cases such asexamples/native.rs. For more details, checkout the originaldocs.

Aren't SANs alone supposed to detect such errors?

Neither of theleak/address/memorysanitizers are sufficient and can detect such errorseasily.In fact, running

RUSTFLAGS="-Zsanitizer=leak" cargo +nightly run --example undetected// ORRUSTFLAGS="-Zsanitizer=address" cargo +nightly run --example undetected

forexamples/undetected.rs which is

unsafe{let alloc =SmartAlloc;let layout =Layout::from_size_align(8,8).unwrap();    alloc.alloc(layout);}

with nosm_dump(true) at the end, does not show anything, mainly because we specified

[profile.dev]opt-level = 0

for the SmartAlloc to work with introspection as opposed to what has been advised to include (at leastopt-level=1)hereto cirvumvent such a limitation but when is done the context gets destroyed. Also

RUSTFLAGS="-Zsanitizer=memory -Zsanitizer-memory-track-origins" cargo +nightly run --example undetected

cannot compile and it throws unhelpful messages

error: failed to run custom build command for `libc v0.2.132`Caused by:  process didn't exit successfully: `/home/workspace/smartalloc-rs/target/debug/build/libc-02d4e594eff5723f/build-script-build` (exit status: 1)  --- stdout  cargo:rerun-if-changed=build.rs  --- stderr  ==186416==WARNING: MemorySanitizer: use-of-uninitialized-value    #0 0x56367729226c  (/home/workspace/smartalloc-rs/target/debug/build/libc-02d4e594eff5723f/build-script-build+0x7a26c) (BuildId: ff090caba1904387acf3f0fecb58801c6fa5caed)    #1 0x56367728e95d  (/home/workspace/smartalloc-rs/target/debug/build/libc-02d4e594eff5723f/build-script-build+0x7695d) (BuildId: ff090caba1904387acf3f0fecb58801c6fa5caed)    ...    Uninitialized value was created by an allocation of '_2' in the stack frame of function '_ZN18build_script_build19rustc_minor_nightly17hfbf53e202478a57bE'      #0 0x563677291e70  (/home/workspace/smartalloc-rs/target/debug/build/libc-02d4e594eff5723f/build-script-build+0x79e70) (BuildId: ff090caba1904387acf3f0fecb58801c6fa5caed)    SUMMARY: MemorySanitizer: use-of-uninitialized-value (/home/workspace/smartalloc-rs/target/debug/build/libc-02d4e594eff5723f/build-script-build+0x7a26c) (BuildId: ff090caba1904387acf3f0fecb58801c6fa5caed)    Exiting

so it needs more work!

Known issue

smartalloc-sys/csrc/smartall.cwrites into the passed filename pointer tracked by#[track_caller] (which is immutable)which is an UB that could result into displaying more garbage after the filename in its report using this binding.

License

Licensed under either of

at your own will.

Contribution

Unless you explicitly state otherwise, any contribution intentionallysubmitted for inclusion in the work by you, as defined in the Apache-2.0license, shall be dual licensed as above, without any additional terms orconditions.

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Orphaned memory buffer detector

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