Re: [PATCH] megaraid: kmemleak: Track page allocation for fusion

Catalin Marinas
2017-09-14T12:55:06Z

On Thu, Sep 14, 2017 at 02:16:46PM +0800, shuwang@redhat.com wrote:
> From: Shu Wang <shuwang@redhat.com>
>
> Kmemleak reports about a thousand false positives for fusion->
> cmd_list[]. Root casue is the cmd_list objects are allocated from
> slab allocator, and stored its pointer in object allocated by page
> allocator. The fix will tell kmemleak to track and scan fusion
> object.
>
> Before patch:
> kmemleak: 1004 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
>
> unreferenced object 0xffff88042584e000 (size 8192):
> backtrace:
> kmemleak_alloc+0x4a/0xa0
> __kmalloc+0xec/0x220
> megasas_alloc_cmdlist_fusion+0x3e/0x140 [megaraid_sas]
> megasas_alloc_cmds_fusion+0x44/0x450 [megaraid_sas]
> megasas_init_adapter_fusion+0x21d/0x6e0 [megaraid_sas]
> megasas_init_fw+0x357/0xd30 [megaraid_sas]
> megasas_probe_one.part.34+0x5be/0x1040 [megaraid_sas]
> megasas_probe_one+0x46/0xc0 [megaraid_sas]
> local_pci_probe+0x45/0xa0
> work_for_cpu_fn+0x14/0x20
> process_one_work+0x149/0x360
> worker_thread+0x1d8/0x3c0
> kthread+0x109/0x140
> ret_from_fork+0x25/0x30
>
> Signed-off-by: Shu Wang <shuwang@redhat.com>
> ---
> drivers/scsi/megaraid/megaraid_sas_fusion.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/scsi/megaraid/megaraid_sas_fusion.c b/drivers/scsi/megaraid/megaraid_sas_fusion.c
> index 11bd2e698b84..621299edd8de 100644
> --- a/drivers/scsi/megaraid/megaraid_sas_fusion.c
> +++ b/drivers/scsi/megaraid/megaraid_sas_fusion.c
> @@ -48,6 +48,7 @@
> #include <linux/mutex.h>
> #include <linux/poll.h>
> #include <linux/vmalloc.h>
> +#include <linux/kmemleak.h>
>
> #include <scsi/scsi.h>
> #include <scsi/scsi_cmnd.h>
> @@ -4512,7 +4513,9 @@ megasas_alloc_fusion_context(struct megasas_instance *instance)
> dev_err(&instance->pdev->dev, "Failed from %s %d\n", __func__, __LINE__);
> return -ENOMEM;
> }
> - }
> + } else
> + kmemleak_alloc(instance->ctrl_context,
> + sizeof(struct fusion_context), 1, GFP_KERNEL);
>
> fusion = instance->ctrl_context;
>
> @@ -4548,9 +4551,11 @@ megasas_free_fusion_context(struct megasas_instance *instance)
>
> if (is_vmalloc_addr(fusion))
> vfree(fusion);
> - else
> + else {
> free_pages((ulong)fusion,
> instance->ctrl_context_pages);
> + kmemleak_free(fusion);
> + }

Apart from Bart's comments on braces and comment before
kmemleak_alloc(), I'd call kmemleak_free() before free_pages(),
otherwise it may not interact nicely with other tools checking for use
after free. With that:

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

--
Catalin