taint/module: Clean up global and module taint flags handling

The commit 66cc69e34e86a231 ("Fix: module signature vs tracepoints:
add new TAINT_UNSIGNED_MODULE") updated module_taint_flags() to
potentially print one more character. But it did not increase the
size of the corresponding buffers in m_show() and print_modules().

We have recently done the same mistake when adding a taint flag
for livepatching, see
https://lkml.kernel.org/r/cfba2c823bb984690b73572aaae1db596b54a082.1472137475.git.jpoimboe@redhat.com

Also struct module uses an incompatible type for mod-taints flags.
It survived from the commit 2bc2d61a9638dab670d ("[PATCH] list module
taint flags in Oops/panic"). There was used "int" for the global taint
flags at these times. But only the global tain flags was later changed
to "unsigned long" by the commit 25ddbb18aae33ad2 ("Make the taint
flags reliable").

This patch defines TAINT_FLAGS_COUNT that can be used to create
arrays and buffers of the right size. Note that we could not use
enum because the taint flag indexes are used also in assembly code.

Then it reworks the table that describes the taint flags. The TAINT_*
numbers can be used as the index. Instead, we add information
if the taint flag is also shown per-module.

Finally, it uses "unsigned long", bit operations, and the updated
taint_flags table also for mod->taints.

It is not optimal because only few taint flags can be printed by
module_taint_flags(). But better be on the safe side. IMHO, it is
not worth the optimization and this is a good compromise.

Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: http://lkml.kernel.org/r/1474458442-21581-1-git-send-email-pmladek@suse.com
[jeyu@redhat.com: fix broken lkml link in changelog]
Signed-off-by: Jessica Yu <jeyu@redhat.com>

1 files changed, 13 insertions, 20 deletions

diff --git a/kernel/module.c b/kernel/module.c
index f57dd63186e6..a4acd8f403ae 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -330,7 +330,7 @@ static inline void add_taint_module(struct module *mod, unsigned flag,
                                     enum lockdep_ok lockdep_ok)
 {
         add_taint(flag, lockdep_ok);
-        mod->taints |= (1U << flag);
+        set_bit(flag, &mod->taints);
 }
 
 /*
@@ -1138,24 +1138,13 @@ static inline int module_unload_init(struct module *mod)
 static size_t module_flags_taint(struct module *mod, char *buf)
 {
         size_t l = 0;
+        int i;
+
+        for (i = 0; i < TAINT_FLAGS_COUNT; i++) {
+                if (taint_flags[i].module && test_bit(i, &mod->taints))
+                        buf[l++] = taint_flags[i].true;
+        }
 
-        if (mod->taints & (1 << TAINT_PROPRIETARY_MODULE))
-                buf[l++] = 'P';
-        if (mod->taints & (1 << TAINT_OOT_MODULE))
-                buf[l++] = 'O';
-        if (mod->taints & (1 << TAINT_FORCED_MODULE))
-                buf[l++] = 'F';
-        if (mod->taints & (1 << TAINT_CRAP))
-                buf[l++] = 'C';
-        if (mod->taints & (1 << TAINT_UNSIGNED_MODULE))
-                buf[l++] = 'E';
-        if (mod->taints & (1 << TAINT_LIVEPATCH))
-                buf[l++] = 'K';
-        /*
-         * TAINT_FORCED_RMMOD: could be added.
-         * TAINT_CPU_OUT_OF_SPEC, TAINT_MACHINE_CHECK, TAINT_BAD_PAGE don't
-         * apply to modules.
-         */
         return l;
 }
 
@@ -4041,6 +4030,10 @@ int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *,
 }
 #endif /* CONFIG_KALLSYMS */
 
+/* Maximum number of characters written by module_flags() */
+#define MODULE_FLAGS_BUF_SIZE (TAINT_FLAGS_COUNT + 4)
+
+/* Keep in sync with MODULE_FLAGS_BUF_SIZE !!! */
 static char *module_flags(struct module *mod, char *buf)
 {
         int bx = 0;
@@ -4085,7 +4078,7 @@ static void m_stop(struct seq_file *m, void *p)
 static int m_show(struct seq_file *m, void *p)
 {
         struct module *mod = list_entry(p, struct module, list);
-        char buf[8];
+        char buf[MODULE_FLAGS_BUF_SIZE];
 
         /* We always ignore unformed modules. */
         if (mod->state == MODULE_STATE_UNFORMED)
@@ -4256,7 +4249,7 @@ EXPORT_SYMBOL_GPL(__module_text_address);
 void print_modules(void)
 {
         struct module *mod;
-        char buf[8];
+        char buf[MODULE_FLAGS_BUF_SIZE];
 
         printk(KERN_DEFAULT "Modules linked in:");
         /* Most callers should already have preempt disabled, but make sure */