linux-kernel - Re: [axboe-block:for-5.17/block 106/108] block/blk-ioc.c:307 set_task_ioprio() error: we previously assumed 'task->io

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Message-ID: <921dd30d-b9d1-c66c-525f-b678a0b97a47@kernel.dk>
Date:   Mon, 20 Dec 2021 20:31:55 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Dan Carpenter <dan.carpenter@...cle.com>, kbuild@...ts.01.org,
        Christoph Hellwig <hch@....de>
Cc:     lkp@...el.com, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org, Jan Kara <jack@...e.cz>
Subject: Re: [axboe-block:for-5.17/block 106/108] block/blk-ioc.c:307
 set_task_ioprio() error: we previously assumed 'task->io_context' could be
 null (see line 300)

On 12/17/21 12:49 AM, Dan Carpenter wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-5.17/block
> head:   5ef1630586317e92c9ebd7b4ce48f393b7ff790f
> commit: 5fc11eebb4a98df5324a4de369bb5ab7f0007ff7 [106/108] block: open code create_task_io_context in set_task_ioprio
> config: i386-randconfig-m021-20211216 (https://download.01.org/0day-ci/archive/20211217/202112171520.5hNnOM0q-lkp@intel.com/config)
> compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
> Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> 
> smatch warnings:
> block/blk-ioc.c:307 set_task_ioprio() error: we previously assumed 'task->io_context' could be null (see line 300)

This should fix it:


diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index 87bdc9ca8295..71c3a933cf16 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -279,7 +279,12 @@ int set_task_ioprio(struct task_struct *task, int ioprio)
 			return -ENOMEM;
 
 		task_lock(task);
-		if (task->io_context || (task->flags & PF_EXITING)) {
+		if (task->flags & PF_EXITING) {
+			err = -ESRCH;
+			kmem_cache_free(iocontext_cachep, ioc);
+			goto out;
+		}
+		if (task->io_context) {
 			kmem_cache_free(iocontext_cachep, ioc);
 			ioc = task->io_context;
 		} else {
@@ -287,8 +292,9 @@ int set_task_ioprio(struct task_struct *task, int ioprio)
 		}
 	}
 	task->io_context->ioprio = ioprio;
+out:
 	task_unlock(task);
-	return 0;
+	return err;
 }
 EXPORT_SYMBOL_GPL(set_task_ioprio);
 

-- 
Jens Axboe