6.6-stable review patch. If anyone has any objections, please let me know.
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From: Fedor Pchelkin pchelkin@ispras.ru
[ Upstream commit bb9025f4432f8c158322cf2c04c2b492f23eb511 ]
kthread creation failure is invalidly handled inside do_map_benchmark(). The put_task_struct() calls on the error path are supposed to balance the get_task_struct() calls which only happen after all the kthreads are successfully created. Rollback using kthread_stop() for already created kthreads in case of such failure.
In normal situation call kthread_stop_put() to gracefully stop kthreads and put their task refcounts. This should be done for all started kthreads.
Found by Linux Verification Center (linuxtesting.org).
Fixes: 65789daa8087 ("dma-mapping: add benchmark support for streaming DMA APIs") Suggested-by: Robin Murphy robin.murphy@arm.com Signed-off-by: Fedor Pchelkin pchelkin@ispras.ru Reviewed-by: Robin Murphy robin.murphy@arm.com Signed-off-by: Christoph Hellwig hch@lst.de Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/dma/map_benchmark.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/kernel/dma/map_benchmark.c b/kernel/dma/map_benchmark.c index 02205ab53b7e9..2478957cf9f83 100644 --- a/kernel/dma/map_benchmark.c +++ b/kernel/dma/map_benchmark.c @@ -118,6 +118,8 @@ static int do_map_benchmark(struct map_benchmark_data *map) if (IS_ERR(tsk[i])) { pr_err("create dma_map thread failed\n"); ret = PTR_ERR(tsk[i]); + while (--i >= 0) + kthread_stop(tsk[i]); goto out; }
@@ -139,13 +141,17 @@ static int do_map_benchmark(struct map_benchmark_data *map)
msleep_interruptible(map->bparam.seconds * 1000);
- /* wait for the completion of benchmark threads */ + /* wait for the completion of all started benchmark threads */ for (i = 0; i < threads; i++) { - ret = kthread_stop(tsk[i]); - if (ret) - goto out; + int kthread_ret = kthread_stop_put(tsk[i]); + + if (kthread_ret) + ret = kthread_ret; }
+ if (ret) + goto out; + loops = atomic64_read(&map->loops); if (likely(loops > 0)) { u64 map_variance, unmap_variance; @@ -170,8 +176,6 @@ static int do_map_benchmark(struct map_benchmark_data *map) }
out: - for (i = 0; i < threads; i++) - put_task_struct(tsk[i]); put_device(map->dev); kfree(tsk); return ret;