lib/generic-radix-tree.c: add kmemleak annotations

Kmemleak is falsely reporting a leak of the slab allocation in
sctp_stream_init_ext():

  BUG: memory leak
  unreferenced object 0xffff8881114f5d80 (size 96):
   comm "syz-executor934", pid 7160, jiffies 4294993058 (age 31.950s)
   hex dump (first 32 bytes):
     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
   backtrace:
     [<00000000ce7a1326>] kmemleak_alloc_recursive  include/linux/kmemleak.h:55 [inline]
     [<00000000ce7a1326>] slab_post_alloc_hook mm/slab.h:439 [inline]
     [<00000000ce7a1326>] slab_alloc mm/slab.c:3326 [inline]
     [<00000000ce7a1326>] kmem_cache_alloc_trace+0x13d/0x280 mm/slab.c:3553
     [<000000007abb7ac9>] kmalloc include/linux/slab.h:547 [inline]
     [<000000007abb7ac9>] kzalloc include/linux/slab.h:742 [inline]
     [<000000007abb7ac9>] sctp_stream_init_ext+0x2b/0xa0  net/sctp/stream.c:157
     [<0000000048ecb9c1>] sctp_sendmsg_to_asoc+0x946/0xa00  net/sctp/socket.c:1882
     [<000000004483ca2b>] sctp_sendmsg+0x2a8/0x990 net/sctp/socket.c:2102
     [...]

But it's freed later.  Kmemleak misses the allocation because its
pointer is stored in the generic radix tree sctp_stream::out, and the
generic radix tree uses raw pages which aren't tracked by kmemleak.

Fix this by adding the kmemleak hooks to the generic radix tree code.

Link: http://lkml.kernel.org/r/20191004065039.727564-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reported-by: <syzbot+7f3b6b106be8dcdcdeec@syzkaller.appspotmail.com>
Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Vlad Yasevich <vyasevich@gmail.com>
Cc: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 26 insertions, 6 deletions

diff --git a/lib/generic-radix-tree.c b/lib/generic-radix-tree.c
index ae25e2fa2187..f25eb111c051 100644
--- a/lib/generic-radix-tree.c
+++ b/lib/generic-radix-tree.c
@@ -2,6 +2,7 @@
 #include <linux/export.h>
 #include <linux/generic-radix-tree.h>
 #include <linux/gfp.h>
+#include <linux/kmemleak.h>
 
 #define GENRADIX_ARY            (PAGE_SIZE / sizeof(struct genradix_node *))
 #define GENRADIX_ARY_SHIFT      ilog2(GENRADIX_ARY)
@@ -75,6 +76,27 @@ void *__genradix_ptr(struct __genradix *radix, size_t offset)
 }
 EXPORT_SYMBOL(__genradix_ptr);
 
+static inline struct genradix_node *genradix_alloc_node(gfp_t gfp_mask)
+{
+        struct genradix_node *node;
+
+        node = (struct genradix_node *)__get_free_page(gfp_mask|__GFP_ZERO);
+
+        /*
+         * We're using pages (not slab allocations) directly for kernel data
+         * structures, so we need to explicitly inform kmemleak of them in order
+         * to avoid false positive memory leak reports.
+         */
+        kmemleak_alloc(node, PAGE_SIZE, 1, gfp_mask);
+        return node;
+}
+
+static inline void genradix_free_node(struct genradix_node *node)
+{
+        kmemleak_free(node);
+        free_page((unsigned long)node);
+}
+
 /*
  * Returns pointer to the specified byte @offset within @radix, allocating it if
  * necessary - newly allocated slots are always zeroed out:
@@ -97,8 +119,7 @@ void *__genradix_ptr_alloc(struct __genradix *radix, size_t offset,
                         break;
 
                 if (!new_node) {
-                        new_node = (void *)
-                                __get_free_page(gfp_mask|__GFP_ZERO);
+                        new_node = genradix_alloc_node(gfp_mask);
                         if (!new_node)
                                 return NULL;
                 }
@@ -121,8 +142,7 @@ void *__genradix_ptr_alloc(struct __genradix *radix, size_t offset,
                 n = READ_ONCE(*p);
                 if (!n) {
                         if (!new_node) {
-                                new_node = (void *)
-                                        __get_free_page(gfp_mask|__GFP_ZERO);
+                                new_node = genradix_alloc_node(gfp_mask);
                                 if (!new_node)
                                         return NULL;
                         }
@@ -133,7 +153,7 @@ void *__genradix_ptr_alloc(struct __genradix *radix, size_t offset,
         }
 
         if (new_node)
-                free_page((unsigned long) new_node);
+                genradix_free_node(new_node);
 
         return &n->data[offset];
 }
@@ -191,7 +211,7 @@ static void genradix_free_recurse(struct genradix_node *n, unsigned level)
                                 genradix_free_recurse(n->children[i], level - 1);
         }
 
-        free_page((unsigned long) n);
+        genradix_free_node(n);
 }
 
 int __genradix_prealloc(struct __genradix *radix, size_t size,