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Subject[PATCH] lib/generic-radix-tree.c: add kmemleak annotations
Date
From: Eric Biggers <ebiggers@google.com>

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.

Reported-by: syzbot+7f3b6b106be8dcdcdeec@syzkaller.appspotmail.com
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
lib/generic-radix-tree.c | 32 ++++++++++++++++++++++++++------
1 file 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,
--
2.23.0
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