ptr_ring: prevent integer overflow when calculating size

BugLink: http://bugs.launchpad.net/bugs/1786352
[ Upstream commit 54e02162d4454a99227f520948bf4494c3d972d0 ]

Switch to use dividing to prevent integer overflow when size is too
big to calculate allocation size properly.

Reported-by: Eric Biggers <ebiggers3@gmail.com>
Fixes: 6e6e41c31122 ("ptr_ring: fail early if queue occupies more than KMALLOC_MAX_SIZE")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
index 59c77c1388aedfd45295109c47c20a52f62c3b12..d0bd988aff7082db32bf05dde7bfb3b8f506342c 100644 (file)
--- a/include/linux/ptr_ring.h
+++ b/include/linux/ptr_ring.h
@@ -456,7 +456,7 @@ static inline int ptr_ring_consume_batched_bh(struct ptr_ring *r,
  */
 static inline void **__ptr_ring_init_queue_alloc(unsigned int size, gfp_t gfp)
 {
-       if (size * sizeof(void *) > KMALLOC_MAX_SIZE)
+       if (size > KMALLOC_MAX_SIZE / sizeof(void *))
                return NULL;
        return kvmalloc_array(size, sizeof(void *), gfp | __GFP_ZERO);
 }