CVE-2011-2502, CVE-2011-2503
This commit is contained in:
Frank Ch. Eigler
parent
6f48688609
commit
b2a6327d24
60
cve-2011-2502.patch
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60
cve-2011-2502.patch
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commit e75e70e736ea53078eaa9fd36a5f7186e3e2235c
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Author: Josh Stone <jistone@redhat.com>
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Date: Fri Jun 24 14:21:26 2011 -0700
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rhbz716476: Don't allow path-based auth for uprobes
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For users that are only members of stapusr, and not stapdev, we only
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allow loading modules that are either signed with a trusted certificate
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or located in controlled paths. For the script itself, that path is
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/lib/modules/.../systemtap/, and for uprobes it is the runtime. When
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this policy was first written, uprobes only ever came from the runtime
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path, so the path check just returned 1 always.
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Later, commit 474d17ad added an optional argument to staprun -u, to
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allow the user to specify their own signed copy of uprobes to load.
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Unfortunately, if presented with an unsigned module, that would still
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fall back to the path check, which blissfully approved it anyway.
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Our policy is now that stapusr can only load a signed uprobes.ko, so the
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path check for uprobes now unconditionally returns 0.
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diff --git a/runtime/staprun/staprun_funcs.c b/runtime/staprun/staprun_funcs.c
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index 74eef9c..82754d4 100644
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--- a/runtime/staprun/staprun_funcs.c
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+++ b/runtime/staprun/staprun_funcs.c
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@@ -387,8 +387,10 @@ check_stap_module_path(const char *module_path, int module_fd)
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}
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/*
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- * Members of the 'stapusr' group can load the uprobes module freely,
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- * since it is loaded from a fixed path in the installed runtime.
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+ * Don't allow path-based authorization for the uprobes module at all.
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+ * Members of the 'stapusr' group can load a signed uprobes module, but
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+ * nothing else. Later we could consider allowing specific paths, like
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+ * the installed runtime or /lib/modules/...
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*
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* Returns: -1 on errors, 0 on failure, 1 on success.
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*/
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@@ -398,7 +400,7 @@ check_uprobes_module_path (
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int module_fd __attribute__ ((unused))
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)
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{
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- return 1;
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+ return 0;
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}
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/*
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@@ -596,10 +598,8 @@ void assert_uprobes_module_permissions(
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if (check_signature_rc == MODULE_ALTERED)
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exit(-1);
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#else
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- /* If we don't have NSS, then the uprobes module is considered trusted.
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- Otherwise a member of the group 'stapusr' will not be able to load it.
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- */
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- check_signature_rc = MODULE_OK;
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+ /* If we don't have NSS, the uprobes module is considered untrusted. */
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+ check_signature_rc = MODULE_UNTRUSTED;
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#endif
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/* root can still load this module. */
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88
cve-2011-2503.patch
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88
cve-2011-2503.patch
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commit fa6b56faaa56c98203dcc3fbdda5eab3d91ec62d
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Author: Josh Stone <jistone@redhat.com>
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Date: Fri Jun 24 15:00:41 2011 -0700
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rhbz716489: read instead of mmap to load modules
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As staprun is preparing to load a kernel module, we first mmap the whole
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module as MAP_PRIVATE. Then we proceed with our security checks,
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including a trusted-signature validation on the mapped region, and if
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all checks out, we'll call init_module() with that same mapped region.
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However, MMAP(2) says of MAP_PRIVATE, "It is unspecified whether changes
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made to the file after the mmap() call are visible in the mapped
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region." From my testing, it appears that file changes do indeed show
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up in our mapped memory. This means we have a TOCTOU race between
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verifying the signature of that memory and then calling init_module().
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By using read() instead of mmap(), we ensure that we have a fully
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private copy of the module to verify and load, without fear of change.
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diff --git a/runtime/staprun/staprun_funcs.c b/runtime/staprun/staprun_funcs.c
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index 74eef9c..e0a5a46 100644
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--- a/runtime/staprun/staprun_funcs.c
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+++ b/runtime/staprun/staprun_funcs.c
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@@ -49,7 +49,7 @@ int insert_module(
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assert_permissions_func assert_permissions
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) {
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int i;
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- long ret;
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+ long ret, module_read;
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void *module_file;
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char *opts;
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int saved_errno;
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@@ -109,17 +109,39 @@ int insert_module(
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return -1;
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}
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- /* mmap in the entire module. Work with the memory mapped data from this
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- point on to avoid a TOCTOU race between path and signature checking
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- below and module loading. */
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- module_file = mmap(NULL, sbuf.st_size, PROT_READ, MAP_PRIVATE, module_fd, 0);
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- if (module_file == MAP_FAILED) {
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- _perr("Error mapping '%s'", module_realpath);
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+ /* Allocate memory for the entire module. */
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+ module_file = calloc(1, sbuf.st_size);
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+ if (module_file == NULL) {
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+ _perr("Error allocating memory to read '%s'", module_realpath);
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close(module_fd);
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free(opts);
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return -1;
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}
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+ /* read in the entire module. Work with this copy of the data from this
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+ point on to avoid a TOCTOU race between path and signature checking
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+ below and module loading. */
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+ module_read = 0;
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+ while (module_read < sbuf.st_size) {
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+ ret = read(module_fd, module_file + module_read,
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+ sbuf.st_size - module_read);
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+ if (ret > 0)
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+ module_read += ret;
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+ else if (ret == 0) {
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+ _err("Unexpected EOF reading '%s'", module_realpath);
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+ free(module_file);
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+ close(module_fd);
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+ free(opts);
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+ return -1;
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+ } else if (errno != EINTR) {
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+ _perr("Error reading '%s'", module_realpath);
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+ free(module_file);
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+ close(module_fd);
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+ free(opts);
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+ return -1;
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+ }
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+ }
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+
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/* Check whether this module can be loaded by the current user.
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* check_permissions will exit(-1) if permissions are insufficient*/
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assert_permissions (module_realpath, module_fd, module_file, sbuf.st_size);
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@@ -131,7 +153,7 @@ int insert_module(
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/* Cleanup. */
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free(opts);
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- munmap(module_file, sbuf.st_size);
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+ free(module_file);
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close(module_fd);
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if (ret != 0) {
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@ -16,7 +16,7 @@
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Name: systemtap
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Version: 1.5
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Release: 7%{?dist}
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Release: 8%{?dist}
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# for version, see also configure.ac
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Summary: Instrumentation System
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Group: Development/System
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@ -68,6 +68,8 @@ BuildRequires: elfutils-devel >= %{elfutils_version}
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Patch2: swbz12899.patch
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Patch3: swbz12927.patch
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Patch4: cve-2011-2502.patch
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Patch5: cve-2011-2503.patch
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%if %{with_docs}
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BuildRequires: /usr/bin/latex /usr/bin/dvips /usr/bin/ps2pdf latex2html
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@ -190,6 +192,8 @@ cd ..
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%patch2 -p1
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%patch3 -p1
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%patch4 -p1
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%patch5 -p1
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%patch25 -p1
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@ -508,6 +512,9 @@ exit 0
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%changelog
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* Mon Jul 25 2011 Frank Ch. Eigler <fche@redhat.com> - 1.5-8
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- CVE-2011-2502, CVE-2011-2503
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* Fri Jul 15 2011 William Cohen <wcohen@redhat.com> - 1.5-7
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- Fix sdt.h to avoid warning on arm arches.
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