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SubjectRe: [PATCH v2] block: fix ioc leak in put_io_context
On Tue, Mar 13, 2012 at 01:21:06PM -0400, Xiaotian Feng wrote:
> When put_io_context is called, if ioc->icq_list is empty and refcount
> is 1, kernel will not free the ioc.
>
> This is caught by following kmemleak:
>
> unreferenced object 0xffff880036349fe0 (size 216):
> comm "sh", pid 2137, jiffies 4294931140 (age 290579.412s)
> hex dump (first 32 bytes):
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> 01 00 01 00 ad 4e ad de ff ff ff ff 00 00 00 00 .....N..........
> backtrace:
> [<ffffffff8169f926>] kmemleak_alloc+0x26/0x50
> [<ffffffff81195a9c>] kmem_cache_alloc_node+0x1cc/0x2a0
> [<ffffffff81356b67>] create_io_context_slowpath+0x27/0x130
> [<ffffffff81356d2b>] get_task_io_context+0xbb/0xf0
> [<ffffffff81055f0e>] copy_process+0x188e/0x18b0
> [<ffffffff8105609b>] do_fork+0x11b/0x420
> [<ffffffff810247f8>] sys_clone+0x28/0x30
> [<ffffffff816d3373>] stub_clone+0x13/0x20
> [<ffffffffffffffff>] 0xffffffffffffffff
>
> ioc should be freed if ioc->icq_list is empty.
> Signed-off-by: Xiaotian Feng <dannyfeng@tencent.com>
> ---
> block/blk-ioc.c | 6 ++++++
> 1 files changed, 6 insertions(+), 0 deletions(-)
>
> diff --git a/block/blk-ioc.c b/block/blk-ioc.c
> index 8b782a6..9690f27 100644
> --- a/block/blk-ioc.c
> +++ b/block/blk-ioc.c
> @@ -145,6 +145,7 @@ static void ioc_release_fn(struct work_struct *work)
> void put_io_context(struct io_context *ioc)
> {
> unsigned long flags;
> + bool free_ioc = false;
>
> if (ioc == NULL)
> return;
> @@ -159,8 +160,13 @@ void put_io_context(struct io_context *ioc)
> spin_lock_irqsave(&ioc->lock, flags);
> if (!hlist_empty(&ioc->icq_list))
> schedule_work(&ioc->release_work);
> + else
> + free_ioc = true;
> spin_unlock_irqrestore(&ioc->lock, flags);
> }
> +
> + if (free_ioc)
> + kmem_cache_free(iocontext_cachep, ioc);
> }
> EXPORT_SYMBOL(put_io_context);

This one looks good to me. Tejun?

Acked-by: Vivek Goyal <vgoyal@redhat.com>

Vivek


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