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unix: Set a guard page at the end of signal stacks #69969

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Merged
merged 3 commits into from
Mar 19, 2020
Merged

unix: Set a guard page at the end of signal stacks #69969

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041d97f
unix: Set a guard page at the end of signal stacks
iximeow Mar 13, 2020
0ca2ed3
return a pointer to the end of the valid part of the sigstack, no fur…
iximeow Mar 13, 2020
28eeea6
fix formatting
iximeow Mar 13, 2020
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23 changes: 18 additions & 5 deletions src/libstd/sys/unix/stack_overflow.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -45,8 +45,9 @@ mod imp {
use libc::{mmap, munmap};
use libc::{sigaction, sighandler_t, SA_ONSTACK, SA_SIGINFO, SIGBUS, SIG_DFL};
use libc::{sigaltstack, SIGSTKSZ, SS_DISABLE};
use libc::{MAP_ANON, MAP_PRIVATE, PROT_READ, PROT_WRITE, SIGSEGV};
use libc::{MAP_ANON, MAP_PRIVATE, PROT_NONE, PROT_READ, PROT_WRITE, SIGSEGV};

use crate::sys::unix::os::page_size;
use crate::sys_common::thread_info;

#[cfg(any(target_os = "linux", target_os = "android"))]
Expand Down Expand Up @@ -137,12 +138,22 @@ mod imp {
}

unsafe fn get_stackp() -> *mut libc::c_void {
let stackp =
mmap(ptr::null_mut(), SIGSTKSZ, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
let stackp = mmap(
ptr::null_mut(),
SIGSTKSZ + page_size(),
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANON,
-1,
0,
);
if stackp == MAP_FAILED {
panic!("failed to allocate an alternative stack");
}
stackp
let guard_result = libc::mprotect(stackp, page_size(), PROT_NONE);
if guard_result != 0 {
panic!("failed to set up alternative stack guard page");
}
stackp.add(page_size())
}

#[cfg(any(
Expand Down Expand Up @@ -190,7 +201,9 @@ mod imp {
ss_size: SIGSTKSZ,
};
sigaltstack(&stack, ptr::null_mut());
munmap(handler._data, SIGSTKSZ);
// We know from `get_stackp` that the alternate stack we installed is part of a mapping
// that started one page earlier, so walk back a page and unmap from there.
munmap(handler._data.sub(page_size()), SIGSTKSZ + page_size());
}
}
}
Expand Down