[glibc] hurd: Map brk non-executable

[glibc] hurd: Map brk non-executable

[Samuel Thibault]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4b5e576fc21931969c0a1b53fdaf7ce3bfcebb86

commit 4b5e576fc21931969c0a1b53fdaf7ce3bfcebb86
Author: Sergey Bugaev <bugaevc@gmail.com>
Date:   Mon Jun 26 02:17:48 2023 +0300

    hurd: Map brk non-executable
    
    The rest of the heap (backed by individual pages) is already mapped RW.
    Mapping these pages RWX presents a security hazard.
    
    Also, in another branch memory gets allocated using vm_allocate, which
    sets memory protection to VM_PROT_DEFAULT (which is RW). The mismatch
    between protections prevents Mach from coalescing the VM map entries.
    
    Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
    Message-Id: <20230625231751.404120-2-bugaevc@gmail.com>

Diff:
---
 sysdeps/mach/hurd/brk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sysdeps/mach/hurd/brk.c b/sysdeps/mach/hurd/brk.c
index f1349495f5..3a335194f5 100644
--- a/sysdeps/mach/hurd/brk.c
+++ b/sysdeps/mach/hurd/brk.c
@@ -106,7 +106,7 @@ _hurd_set_brk (vm_address_t addr)
 	/* First finish allocation.  */
 	err = __vm_protect (__mach_task_self (), pagebrk,
 			    alloc_start - pagebrk, 0,
-			    VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE);
+			    VM_PROT_READ|VM_PROT_WRITE);
       if (! err)
 	_hurd_brk = alloc_start;
 
@@ -120,7 +120,7 @@ _hurd_set_brk (vm_address_t addr)
   else
     /* Make the memory accessible.  */
     err = __vm_protect (__mach_task_self (), pagebrk, pagend - pagebrk,
-			0, VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE);
+			0, VM_PROT_READ|VM_PROT_WRITE);
 
   if (err)
     return __hurd_fail (err);