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Remove padding bytes risk in dbghelp with MaybeUninit #737

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Merged
merged 2 commits into from
Sep 26, 2025
Merged

Remove padding bytes risk in dbghelp with MaybeUninit #737

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05ad047
Remove padding bytes risk in dbghelp with MaybeUninit
workingjubilee Sep 25, 2025
06dca9a
Expand doc-comment on `do_resolve`
workingjubilee Sep 26, 2025
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24 changes: 16 additions & 8 deletions src/symbolize/dbghelp.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,9 +19,10 @@

use super::super::{dbghelp, windows_sys::*};
use super::{BytesOrWideString, ResolveWhat, SymbolName};
use core::cmp;
use core::ffi::c_void;
use core::marker;
use core::mem;
use core::mem::{self, MaybeUninit};
use core::ptr;
use core::slice;

Expand Down Expand Up @@ -217,19 +218,23 @@ unsafe fn resolve_with_inline(
Some(())
}

/// This function is only meant to be called with certain Windows API functions as its arguments,
/// using closures to simplify away here-unspecified arguments:
/// - `sym_from_addr`: either `SymFromAddrW` or `SymFromInlineContextW`
/// - `get_line_from_addr`: `SymGetLineFromAddrW64` or `SymGetLineFromInlineContextW`
unsafe fn do_resolve(
sym_from_addr: impl FnOnce(*mut SYMBOL_INFOW) -> BOOL,
get_line_from_addr: impl FnOnce(&mut IMAGEHLP_LINEW64) -> BOOL,
cb: &mut dyn FnMut(&super::Symbol),
) {
const SIZE: usize = 2 * MAX_SYM_NAME as usize + mem::size_of::<SYMBOL_INFOW>();
let mut data = Aligned8([0u8; SIZE]);
let info = unsafe { &mut *data.0.as_mut_ptr().cast::<SYMBOL_INFOW>() };
info.MaxNameLen = MAX_SYM_NAME as u32;
let mut data = MaybeUninit::<Aligned8<[u8; SIZE]>>::zeroed();
let info = data.as_mut_ptr().cast::<SYMBOL_INFOW>();
unsafe { (*info).MaxNameLen = MAX_SYM_NAME as u32 };
// the struct size in C. the value is different to
// `size_of::<SYMBOL_INFOW>() - MAX_SYM_NAME + 1` (== 81)
// due to struct alignment.
info.SizeOfStruct = 88;
unsafe { (*info).SizeOfStruct = 88 };

if sym_from_addr(info) != TRUE {
return;
Expand All @@ -238,8 +243,10 @@ unsafe fn do_resolve(
// If the symbol name is greater than MaxNameLen, SymFromAddrW will
// give a buffer of (MaxNameLen - 1) characters and set NameLen to
// the real value.
let name_len = ::core::cmp::min(info.NameLen as usize, info.MaxNameLen as usize - 1);
let name_ptr = info.Name.as_ptr().cast::<u16>();
// SAFETY: We assume NameLen has been initialized by SymFromAddrW, and we initialized MaxNameLen
let name_len = unsafe { cmp::min((*info).NameLen as usize, (*info).MaxNameLen as usize - 1) };
// Name must be initialized by SymFromAddrW, but we only interact with it as a pointer anyways.
let name_ptr = (&raw const (*info).Name).cast::<u16>();

// Reencode the utf-16 symbol to utf-8 so we can use `SymbolName::new` like
// all other platforms
Expand Down Expand Up @@ -296,7 +303,8 @@ unsafe fn do_resolve(
cb(&super::Symbol {
inner: Symbol {
name,
addr: info.Address as *mut _,
// SAFETY: we assume Address has been initialized by SymFromAddrW
addr: unsafe { (*info).Address } as *mut _,
line: lineno,
filename,
_filename_cache: unsafe { cache(filename) },
Expand Down
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