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>

2 files changed, 2 insertions, 2 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 749588a50a5a..a2cd47d89e0a 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 f3f6e0758562..1ddb77ba3995 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);