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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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