Date: Thu, 13 Jun 2002 12:20:04 -0700 (PDT) From: Peter Edwards <peter.edwards@openet-telecom.com> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/37554: [PATCH] Make ELF shared libraries immutable once loaded (like executables) Message-ID: <200206131920.g5DJK4V67244@freefall.freebsd.org>
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The following reply was made to PR kern/37554; it has been noted by GNATS.
From: Peter Edwards <peter.edwards@openet-telecom.com>
To: freebsd-gnats-submit@FreeBSD.org, pmedwards@eircom.net
Cc:
Subject: Re: kern/37554: [PATCH] Make ELF shared libraries immutable once
loaded (like executables)
Date: Thu, 13 Jun 2002 20:19:11 +0100
Hm. This is possibly a nicer way to do it, and certainly a smaller, if more
intrusive, patch. It changes the semantics of mmap() somewhat, but I think
in a reasonable way, and it avoids all that ugliness in the run-time linker.
Basically, a request for PROT_EXEC on a regular file will cause it to become
immutable:
--- vm_mmap.c 3 Nov 2001 01:41:10 -0000 1.108.2.5
+++ vm_mmap.c 13 Jun 2002 19:15:28 -0000
@@ -406,8 +406,17 @@
error = vm_mmap(&vms->vm_map, &addr, size, prot, maxprot,
flags, handle, pos);
- if (error == 0)
+ if (error == 0) {
p->p_retval[0] = (register_t) (addr + pageoff);
+ /*
+ * A successful map for a regular file, with execute access:
+ * mark the vnode immutable.
+ * XXX: GCC warns, but (handle == 0 || handle == vp)
+ * I'm not sure of the "correct" way to avoid this.
+ */
+ if (handle && vp->v_type == VREG && (prot & PROT_EXEC))
+ vp->v_flag |= VTEXT;
+ }
done:
if (fp)
fdrop(fp, p);
Of course, the utility of all this is questionable: I just wanted the
functionality for something locally.
Cheers,
Peter
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