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SubjectRe: [PATCH] block: fix ioc leak in put_io_context
On Mon, Mar 12, 2012 at 10:59:18AM -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->release_work() should be used even if ioc->icq_list is empty.
>
> Signed-off-by: Xiaotian Feng <dannyfeng@tencent.com>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Jens Axboe <axboe@kernel.dk>
> ---
> block/blk-ioc.c | 3 +--
> 1 files changed, 1 insertions(+), 2 deletions(-)
>
> diff --git a/block/blk-ioc.c b/block/blk-ioc.c
> index 8b782a6..d74a8ce 100644
> --- a/block/blk-ioc.c
> +++ b/block/blk-ioc.c
> @@ -157,8 +157,7 @@ void put_io_context(struct io_context *ioc)
> */
> if (atomic_long_dec_and_test(&ioc->refcount)) {
> spin_lock_irqsave(&ioc->lock, flags);
> - if (!hlist_empty(&ioc->icq_list))
> - schedule_work(&ioc->release_work);
> + schedule_work(&ioc->release_work);
> spin_unlock_irqrestore(&ioc->lock, flags);

May be free the ioc right here instead of invoking release_work().

Thanks
Vivek


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