kfence: fix reports if constant function prefixes exist

Some architectures prefix all functions with a constant string ('.' on
ppc64).  Add ARCH_FUNC_PREFIX, which may optionally be defined in
<asm/kfence.h>, so that get_stack_skipnr() can work properly.

Link: https://lkml.kernel.org/r/f036c53d-7e81-763c-47f4-6024c6c5f058@csgroup.eu
Link: https://lkml.kernel.org/r/20210304144000.1148590-1-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Reported-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Tested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/kfence/report.c b/mm/kfence/report.c
index 519f037..e3f7145 100644 (file)
--- a/mm/kfence/report.c
+++ b/mm/kfence/report.c
@@ -20,6 +20,11 @@
 
 #include "kfence.h"
 
+/* May be overridden by <asm/kfence.h>. */
+#ifndef ARCH_FUNC_PREFIX
+#define ARCH_FUNC_PREFIX ""
+#endif
+
 extern bool no_hash_pointers;
 
 /* Helper function to either print to a seq_file or to console. */
@@ -67,8 +72,9 @@ static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries
        for (skipnr = 0; skipnr < num_entries; skipnr++) {
                int len = scnprintf(buf, sizeof(buf), "%ps", (void *)stack_entries[skipnr]);
 
-               if (str_has_prefix(buf, "kfence_") || str_has_prefix(buf, "__kfence_") ||
-                   !strncmp(buf, "__slab_free", len)) {
+               if (str_has_prefix(buf, ARCH_FUNC_PREFIX "kfence_") ||
+                   str_has_prefix(buf, ARCH_FUNC_PREFIX "__kfence_") ||
+                   !strncmp(buf, ARCH_FUNC_PREFIX "__slab_free", len)) {
                        /*
                         * In case of tail calls from any of the below
                         * to any of the above.
@@ -77,10 +83,10 @@ static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries
                }
 
                /* Also the *_bulk() variants by only checking prefixes. */
-               if (str_has_prefix(buf, "kfree") ||
-                   str_has_prefix(buf, "kmem_cache_free") ||
-                   str_has_prefix(buf, "__kmalloc") ||
-                   str_has_prefix(buf, "kmem_cache_alloc"))
+               if (str_has_prefix(buf, ARCH_FUNC_PREFIX "kfree") ||
+                   str_has_prefix(buf, ARCH_FUNC_PREFIX "kmem_cache_free") ||
+                   str_has_prefix(buf, ARCH_FUNC_PREFIX "__kmalloc") ||
+                   str_has_prefix(buf, ARCH_FUNC_PREFIX "kmem_cache_alloc"))
                        goto found;
        }
        if (fallback < num_entries)