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Re: /dev/ksyms permissions



Maxime Villard <max%M00nBSD.net@localhost> writes:

> Well, looking at the code, it seems to me that _kvm_open() should be
> changed to keep /dev/ksyms open, the same way it keeps /dev/kmem open.

Agreed.  This works fine for me, with and without /dev/ksyms present:

Index: lib/libkvm/kvm.c
===================================================================
RCS file: /cvsroot/src/lib/libkvm/kvm.c,v
retrieving revision 1.102
diff -u -u -r1.102 kvm.c
--- lib/libkvm/kvm.c	29 Mar 2016 06:51:40 -0000	1.102
+++ lib/libkvm/kvm.c	18 Jan 2018 12:41:56 -0000
@@ -322,15 +322,6 @@
 		strlcpy(kd->kernelname, uf, sizeof(kd->kernelname));
 	} else {
 		strlcpy(kd->kernelname, _PATH_KSYMS, sizeof(kd->kernelname));
-		/*
-		 * We're here because /dev/ksyms was opened
-		 * successfully.  However, we don't want to keep it
-		 * open, so we close it now.  Later, we will open
-		 * it again, since it will be the only case where
-		 * kd->nlfd is negative.
-		 */
-		close(kd->nlfd);
-		kd->nlfd = -1;
 	}
 
 	if ((kd->pmfd = open(mf, flag | O_CLOEXEC, 0)) < 0) {
@@ -769,33 +760,16 @@
 int
 kvm_nlist(kvm_t *kd, struct nlist *nl)
 {
-	int rv, nlfd;
-
-	/*
-	 * kd->nlfd might be negative when we get here, and in that
-	 * case that means that we're using /dev/ksyms.
-	 * So open it again, just for the time we retrieve the list.
-	 */
-	if (kd->nlfd < 0) {
-		nlfd = open(_PATH_KSYMS, O_RDONLY | O_CLOEXEC, 0);
-		if (nlfd < 0) {
-			_kvm_err(kd, 0, "failed to open %s", _PATH_KSYMS);
-			return (nlfd);
-		}
-	} else
-		nlfd = kd->nlfd;
+	int rv;
 
 	/*
 	 * Call the nlist(3) routines to retrieve the given namelist.
 	 */
-	rv = __fdnlist(nlfd, nl);
+	rv = __fdnlist(kd->nlfd, nl);
 
 	if (rv == -1)
 		_kvm_err(kd, 0, "bad namelist");
 
-	if (kd->nlfd < 0)
-		close(nlfd);
-
 	return (rv);
 }
 

-tih
-- 
Most people who graduate with CS degrees don't understand the significance
of Lisp.  Lisp is the most important idea in computer science.  --Alan Kay

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