diff options
| -rw-r--r-- | src/sys/signal.rs | 59 |
1 files changed, 51 insertions, 8 deletions
diff --git a/src/sys/signal.rs b/src/sys/signal.rs index 0911cfaa..cbd5cfbe 100644 --- a/src/sys/signal.rs +++ b/src/sys/signal.rs @@ -584,9 +584,31 @@ impl SigAction { match self.sigaction.sa_sigaction { libc::SIG_DFL => SigHandler::SigDfl, libc::SIG_IGN => SigHandler::SigIgn, - f if self.flags().contains(SaFlags::SA_SIGINFO) => - SigHandler::SigAction( unsafe { mem::transmute(f) } ), - f => SigHandler::Handler( unsafe { mem::transmute(f) } ), + p if self.flags().contains(SaFlags::SA_SIGINFO) => + SigHandler::SigAction( + // Safe for one of two reasons: + // * The SigHandler was created by SigHandler::new, in which + // case the pointer is correct, or + // * The SigHandler was created by signal or sigaction, which + // are unsafe functions, so the caller should've somehow + // ensured that it is correctly initialized. + unsafe{ + *(&p as *const usize + as *const extern fn(_, _, _)) + } + as extern fn(_, _, _)), + p => SigHandler::Handler( + // Safe for one of two reasons: + // * The SigHandler was created by SigHandler::new, in which + // case the pointer is correct, or + // * The SigHandler was created by signal or sigaction, which + // are unsafe functions, so the caller should've somehow + // ensured that it is correctly initialized. + unsafe{ + *(&p as *const usize + as *const extern fn(libc::c_int)) + } + as extern fn(libc::c_int)), } } @@ -596,7 +618,18 @@ impl SigAction { match self.sigaction.sa_handler { libc::SIG_DFL => SigHandler::SigDfl, libc::SIG_IGN => SigHandler::SigIgn, - f => SigHandler::Handler( unsafe { mem::transmute(f) } ), + p => SigHandler::Handler( + // Safe for one of two reasons: + // * The SigHandler was created by SigHandler::new, in which + // case the pointer is correct, or + // * The SigHandler was created by signal or sigaction, which + // are unsafe functions, so the caller should've somehow + // ensured that it is correctly initialized. + unsafe{ + *(&p as *const usize + as *const extern fn(libc::c_int)) + } + as extern fn(libc::c_int)), } } } @@ -608,9 +641,16 @@ impl SigAction { /// /// # Safety /// -/// Signal handlers may be called at any point during execution, which limits what is safe to do in -/// the body of the signal-catching function. Be certain to only make syscalls that are explicitly -/// marked safe for signal handlers and only share global data using atomics. +/// * Signal handlers may be called at any point during execution, which limits +/// what is safe to do in the body of the signal-catching function. Be certain +/// to only make syscalls that are explicitly marked safe for signal handlers +/// and only share global data using atomics. +/// +/// * There is also no guarantee that the old signal handler was installed +/// correctly. If it was installed by this crate, it will be. But if it was +/// installed by, for example, C code, then there is no guarantee its function +/// pointer is valid. In that case, this function effectively dereferences a +/// raw pointer of unknown provenance. pub unsafe fn sigaction(signal: Signal, sigaction: &SigAction) -> Result<SigAction> { let mut oldact = mem::MaybeUninit::<libc::sigaction>::uninit(); @@ -689,7 +729,10 @@ pub unsafe fn signal(signal: Signal, handler: SigHandler) -> Result<SigHandler> match oldhandler { libc::SIG_DFL => SigHandler::SigDfl, libc::SIG_IGN => SigHandler::SigIgn, - f => SigHandler::Handler(mem::transmute(f)), + p => SigHandler::Handler( + *(&p as *const usize + as *const extern fn(libc::c_int)) + as extern fn(libc::c_int)), } }) } |