From 66cc69e34e86a231fbe68d8918c6119e3b7549a3 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Thu, 13 Mar 2014 12:11:30 +1030 Subject: 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 Acked-by: Steven Rostedt NAKed-by: Ingo Molnar CC: Thomas Gleixner CC: David Howells CC: Greg Kroah-Hartman Signed-off-by: Rusty Russell --- kernel/module.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'kernel/module.c') diff --git a/kernel/module.c b/kernel/module.c index efa1e6031950..c1acb0c5b637 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -1013,6 +1013,8 @@ static size_t module_flags_taint(struct module *mod, char *buf) buf[l++] = 'F'; if (mod->taints & (1 << TAINT_CRAP)) buf[l++] = 'C'; + if (mod->taints & (1 << TAINT_UNSIGNED_MODULE)) + buf[l++] = 'X'; /* * TAINT_FORCED_RMMOD: could be added. * TAINT_UNSAFE_SMP, TAINT_MACHINE_CHECK, TAINT_BAD_PAGE don't @@ -3214,7 +3216,7 @@ static int load_module(struct load_info *info, const char __user *uargs, pr_notice_once("%s: module verification failed: signature " "and/or required key missing - tainting " "kernel\n", mod->name); - add_taint_module(mod, TAINT_FORCED_MODULE, LOCKDEP_STILL_OK); + add_taint_module(mod, TAINT_UNSIGNED_MODULE, LOCKDEP_STILL_OK); } #endif -- cgit