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authorMathieu Desnoyers <mathieu.desnoyers@efficios.com>2014-03-13 05:41:30 +0400
committerRusty Russell <rusty@rustcorp.com.au>2014-03-13 05:41:51 +0400
commit66cc69e34e86a231fbe68d8918c6119e3b7549a3 (patch)
treec1ea795511e9ed8ab83fda895f0151000b166629 /kernel/tracepoint.c
parentcff26a51da5d206d3baf871e75778da44710219d (diff)
downloadlinux-66cc69e34e86a231fbe68d8918c6119e3b7549a3.tar.xz
Fix: module signature vs tracepoints: add new TAINT_UNSIGNED_MODULE
Users have reported being unable to trace non-signed modules loaded within a kernel supporting module signature. This is caused by tracepoint.c:tracepoint_module_coming() refusing to take into account tracepoints sitting within force-loaded modules (TAINT_FORCED_MODULE). The reason for this check, in the first place, is that a force-loaded module may have a struct module incompatible with the layout expected by the kernel, and can thus cause a kernel crash upon forced load of that module on a kernel with CONFIG_TRACEPOINTS=y. Tracepoints, however, specifically accept TAINT_OOT_MODULE and TAINT_CRAP, since those modules do not lead to the "very likely system crash" issue cited above for force-loaded modules. With kernels having CONFIG_MODULE_SIG=y (signed modules), a non-signed module is tainted re-using the TAINT_FORCED_MODULE taint flag. Unfortunately, this means that Tracepoints treat that module as a force-loaded module, and thus silently refuse to consider any tracepoint within this module. Since an unsigned module does not fit within the "very likely system crash" category of tainting, add a new TAINT_UNSIGNED_MODULE taint flag to specifically address this taint behavior, and accept those modules within Tracepoints. We use the letter 'X' as a taint flag character for a module being loaded that doesn't know how to sign its name (proposed by Steven Rostedt). Also add the missing 'O' entry to trace event show_module_flags() list for the sake of completeness. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> NAKed-by: Ingo Molnar <mingo@redhat.com> CC: Thomas Gleixner <tglx@linutronix.de> CC: David Howells <dhowells@redhat.com> CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'kernel/tracepoint.c')
-rw-r--r--kernel/tracepoint.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 031cc5655a51..3cdbed1fbdc7 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -633,7 +633,8 @@ EXPORT_SYMBOL_GPL(tracepoint_iter_reset);
#ifdef CONFIG_MODULES
bool trace_module_has_bad_taint(struct module *mod)
{
- return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP));
+ return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) |
+ (1 << TAINT_UNSIGNED_MODULE));
}
static int tracepoint_module_coming(struct module *mod)
@@ -644,7 +645,7 @@ static int tracepoint_module_coming(struct module *mod)
/*
* We skip modules that taint the kernel, especially those with different
* module headers (for forced load), to make sure we don't cause a crash.
- * Staging and out-of-tree GPL modules are fine.
+ * Staging, out-of-tree, and unsigned GPL modules are fine.
*/
if (trace_module_has_bad_taint(mod))
return 0;