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Subject[PATCH v2] block: fix ioc leak in put_io_context
Date
    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);

--
1.7.5.4


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