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authorMathieu Desnoyers <mathieu.desnoyers@efficios.com>2014-03-13 12:11:30 +1030
committerRusty Russell <rusty@rustcorp.com.au>2014-03-13 12:11:51 +1030
commit66cc69e34e86a231fbe68d8918c6119e3b7549a3 (patch)
treec1ea795511e9ed8ab83fda895f0151000b166629
parentcff26a51da5d206d3baf871e75778da44710219d (diff)
downloadlinux-66cc69e34e86a231fbe68d8918c6119e3b7549a3.tar.gz
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>
-rw-r--r--Documentation/ABI/testing/sysfs-module1
-rw-r--r--Documentation/module-signing.txt3
-rw-r--r--Documentation/oops-tracing.txt3
-rw-r--r--Documentation/sysctl/kernel.txt2
-rw-r--r--include/linux/kernel.h1
-rw-r--r--include/trace/events/module.h4
-rw-r--r--kernel/module.c4
-rw-r--r--kernel/panic.c2
-rw-r--r--kernel/tracepoint.c5
9 files changed, 20 insertions, 5 deletions
diff --git a/Documentation/ABI/testing/sysfs-module b/Documentation/ABI/testing/sysfs-module
index 47064c2b1f79..b9a29cdbaccb 100644
--- a/Documentation/ABI/testing/sysfs-module
+++ b/Documentation/ABI/testing/sysfs-module
@@ -49,3 +49,4 @@ Description: Module taint flags:
O - out-of-tree module
F - force-loaded module
C - staging driver module
+ X - unsigned module
diff --git a/Documentation/module-signing.txt b/Documentation/module-signing.txt
index 2b40e04d3c49..b6af42e4d790 100644
--- a/Documentation/module-signing.txt
+++ b/Documentation/module-signing.txt
@@ -53,7 +53,8 @@ This has a number of options available:
If this is off (ie. "permissive"), then modules for which the key is not
available and modules that are unsigned are permitted, but the kernel will
- be marked as being tainted.
+ be marked as being tainted, and the concerned modules will be marked as
+ tainted, shown with the character 'X'.
If this is on (ie. "restrictive"), only modules that have a valid
signature that can be verified by a public key in the kernel's possession
diff --git a/Documentation/oops-tracing.txt b/Documentation/oops-tracing.txt
index 13032c0140d4..879abe289523 100644
--- a/Documentation/oops-tracing.txt
+++ b/Documentation/oops-tracing.txt
@@ -265,6 +265,9 @@ characters, each representing a particular tainted value.
13: 'O' if an externally-built ("out-of-tree") module has been loaded.
+ 14: 'X' if an unsigned module has been loaded in a kernel supporting
+ module signature.
+
The primary reason for the 'Tainted: ' string is to tell kernel
debuggers if this is a clean kernel or if anything unusual has
occurred. Tainting is permanent: even if an offending module is
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index e55124e7c40c..8ebe1c047004 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -792,6 +792,8 @@ can be ORed together:
1024 - A module from drivers/staging was loaded.
2048 - The system is working around a severe firmware bug.
4096 - An out-of-tree module has been loaded.
+8192 - An unsigned module has been loaded in a kernel supporting module
+ signature.
==============================================================
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 196d1ea86df0..471090093c67 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -469,6 +469,7 @@ extern enum system_states {
#define TAINT_CRAP 10
#define TAINT_FIRMWARE_WORKAROUND 11
#define TAINT_OOT_MODULE 12
+#define TAINT_UNSIGNED_MODULE 13
extern const char hex_asc[];
#define hex_asc_lo(x) hex_asc[((x) & 0x0f)]
diff --git a/include/trace/events/module.h b/include/trace/events/module.h
index 161932737416..11fd51b413de 100644
--- a/include/trace/events/module.h
+++ b/include/trace/events/module.h
@@ -22,8 +22,10 @@ struct module;
#define show_module_flags(flags) __print_flags(flags, "", \
{ (1UL << TAINT_PROPRIETARY_MODULE), "P" }, \
+ { (1UL << TAINT_OOT_MODULE), "O" }, \
{ (1UL << TAINT_FORCED_MODULE), "F" }, \
- { (1UL << TAINT_CRAP), "C" })
+ { (1UL << TAINT_CRAP), "C" }, \
+ { (1UL << TAINT_UNSIGNED_MODULE), "X" })
TRACE_EVENT(module_load,
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
diff --git a/kernel/panic.c b/kernel/panic.c
index 6d6300375090..0e25fe10871e 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -210,6 +210,7 @@ static const struct tnt tnts[] = {
{ TAINT_CRAP, 'C', ' ' },
{ TAINT_FIRMWARE_WORKAROUND, 'I', ' ' },
{ TAINT_OOT_MODULE, 'O', ' ' },
+ { TAINT_UNSIGNED_MODULE, 'X', ' ' },
};
/**
@@ -228,6 +229,7 @@ static const struct tnt tnts[] = {
* 'C' - modules from drivers/staging are loaded.
* 'I' - Working around severe firmware bug.
* 'O' - Out-of-tree module has been loaded.
+ * 'X' - Unsigned module has been loaded.
*
* The string is overwritten by the next call to print_tainted().
*/
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;