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unix: Unsafe-wrap stack_overflow::signal_handler

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sometimes a safety comment is a prayer.
avoid fuzzy provenance casts after deref.

Co-authored-by: Jonas Böttiger <jonasboettiger@icloud.com>
This commit is contained in:
Jubilee Young 2024-07-16 19:31:23 -07:00
parent 7d356ebde3
commit 9e354daf7b
1 changed files with 10 additions and 3 deletions
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13
library/std/src/sys/pal/unix/stack_overflow.rs
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@ -86,13 +86,18 @@ mod imp {
// out many large systems and all implementations allow returning from a
// signal handler to work. For a more detailed explanation see the
// comments on #26458.
/// SIGSEGV/SIGBUS entry point
/// # Safety
/// Rust doesn't call this, it *gets called*.
#[forbid(unsafe_op_in_unsafe_fn)]
unsafe extern "C" fn signal_handler(
signum: libc::c_int,
info: *mut libc::siginfo_t,
_data: *mut libc::c_void,
) {
let (start, end) = GUARD.get();
let addr = (*info).si_addr() as usize;
// SAFETY: this pointer is provided by the system and will always point to a valid `siginfo_t`.
let addr = unsafe { (*info).si_addr().addr() };
// If the faulting address is within the guard page, then we print a
// message saying so and abort.
@ -104,9 +109,11 @@ mod imp {
rtabort!("stack overflow");
} else {
// Unregister ourselves by reverting back to the default behavior.
let mut action: sigaction = mem::zeroed();
// SAFETY: assuming all platforms define struct sigaction as "zero-initializable"
let mut action: sigaction = unsafe { mem::zeroed() };
action.sa_sigaction = SIG_DFL;
sigaction(signum, &action, ptr::null_mut());
// SAFETY: pray this is a well-behaved POSIX implementation of fn sigaction
unsafe { sigaction(signum, &action, ptr::null_mut()) };
// See comment above for why this function returns.
}