KSYM_SYMBOL_LEN fixes

Miles Lane tailing /sys files hit a BUG which Pekka Enberg has tracked
to my 966c8c12dc9e77f931e2281ba25d2f0244b06949 sprint_symbol(): use
less stack exposing a bug in slub's list_locations() -
kallsyms_lookup() writes a 0 to namebuf[KSYM_NAME_LEN-1], but that was
beyond the end of page provided.

The 100 slop which list_locations() allows at end of page looks roughly
enough for all the other stuff it might print after the symbol before
it checks again: break out KSYM_SYMBOL_LEN earlier than before.

Latencytop and ftrace and are using KSYM_NAME_LEN buffers where they
need KSYM_SYMBOL_LEN buffers, and vmallocinfo a 2*KSYM_NAME_LEN buffer
where it wants a KSYM_SYMBOL_LEN buffer: fix those before anyone copies
them.

[akpm@linux-foundation.org: ftrace.h needs module.h]
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc Miles Lane <miles.lane@gmail.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5 files changed, 6 insertions, 5 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 486cf3fe713..d4677603c88 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -371,7 +371,7 @@ static int lstats_show_proc(struct seq_file *m, void *v)
                                 task->latency_record[i].time,
                                 task->latency_record[i].max);
                         for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
-                                char sym[KSYM_NAME_LEN];
+                                char sym[KSYM_SYMBOL_LEN];
                                 char *c;
                                 if (!task->latency_record[i].backtrace[q])
                                         break;
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 703eb53cfa2..9c5bc6be2b0 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -6,6 +6,7 @@
 #include <linux/ktime.h>
 #include <linux/init.h>
 #include <linux/types.h>
+#include <linux/module.h>
 #include <linux/kallsyms.h>
 
 #ifdef CONFIG_FUNCTION_TRACER
@@ -231,7 +232,7 @@ ftrace_init_module(unsigned long *start, unsigned long *end) { }
 
 struct boot_trace {
         pid_t                   caller;
-        char                    func[KSYM_NAME_LEN];
+        char                    func[KSYM_SYMBOL_LEN];
         int                     result;
         unsigned long long      duration;               /* usecs */
         ktime_t                 calltime;
diff --git a/kernel/latencytop.c b/kernel/latencytop.c
index 5e7b45c5692..449db466bdb 100644
--- a/kernel/latencytop.c
+++ b/kernel/latencytop.c
@@ -191,7 +191,7 @@ static int lstats_show(struct seq_file *m, void *v)
                                 latency_record[i].time,
                                 latency_record[i].max);
                         for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
-                                char sym[KSYM_NAME_LEN];
+                                char sym[KSYM_SYMBOL_LEN];
                                 char *c;
                                 if (!latency_record[i].backtrace[q])
                                         break;
diff --git a/mm/slub.c b/mm/slub.c
index 749588a50a5..a2cd47d89e0 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3597,7 +3597,7 @@ static int list_locations(struct kmem_cache *s, char *buf,
         for (i = 0; i < t.count; i++) {
                 struct location *l = &t.loc[i];
 
-                if (len > PAGE_SIZE - 100)
+                if (len > PAGE_SIZE - KSYM_SYMBOL_LEN - 100)
                         break;
                 len += sprintf(buf + len, "%7ld ", l->count);
 
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index f3f6e075856..1ddb77ba399 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1717,7 +1717,7 @@ static int s_show(struct seq_file *m, void *p)
                 v->addr, v->addr + v->size, v->size);
 
         if (v->caller) {
-                char buff[2 * KSYM_NAME_LEN];
+                char buff[KSYM_SYMBOL_LEN];
 
                 seq_putc(m, ' ');
                 sprint_symbol(buff, (unsigned long)v->caller);