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MFC r256504:

Add a sysctl kern.disallow_high_osrel which disables executing the
images compiled on the world with higher major version number than the
high version number of the booted kernel.  Default to disable.

Approved by:	re (glebius)
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1 parent 3056ea9 commit 47b928f216400825cad00e3435e0c50fcb7ebb58 @kostikbel kostikbel committed Oct 25, 2013
Showing with 16 additions and 0 deletions.
  1. +14 −0 sys/kern/kern_exec.c
  2. +2 −0 sys/sys/param.h
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@@ -123,6 +123,11 @@ u_long ps_arg_cache_limit = PAGE_SIZE / 16;
SYSCTL_ULONG(_kern, OID_AUTO, ps_arg_cache_limit, CTLFLAG_RW,
&ps_arg_cache_limit, 0, "");
+static int disallow_high_osrel;
+SYSCTL_INT(_kern, OID_AUTO, disallow_high_osrel, CTLFLAG_RW,
+ &disallow_high_osrel, 0,
+ "Disallow execution of binaries built for higher version of the world");
+
static int map_at_zero = 0;
TUNABLE_INT("security.bsd.map_at_zero", &map_at_zero);
SYSCTL_INT(_security_bsd, OID_AUTO, map_at_zero, CTLFLAG_RW, &map_at_zero, 0,
@@ -552,6 +557,15 @@ do_execve(td, args, mac_p)
vn_fullpath(td, imgp->vp, &imgp->execpath, &imgp->freepath) != 0))
imgp->execpath = args->fname;
+ if (disallow_high_osrel &&
+ P_OSREL_MAJOR(p->p_osrel) > P_OSREL_MAJOR(__FreeBSD_version)) {
+ error = ENOEXEC;
+ uprintf("Osrel %d for image %s too high\n", p->p_osrel,
+ imgp->execpath != NULL ? imgp->execpath : "<unresolved>");
+ vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
+ goto exec_fail_dealloc;
+ }
+
/*
* Copy out strings (args and env) and initialize stack base
*/
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@@ -80,6 +80,8 @@
#define P_OSREL_SIGWAIT 700000
#define P_OSREL_SIGSEGV 700004
#define P_OSREL_MAP_ANON 800104
+
+#define P_OSREL_MAJOR(x) ((x) / 100000)
#endif
#ifndef LOCORE

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