* [PATCH] fs: nfs: Fix a sleep-in-atomic bug in nfs_access_add_cache
@ 2017-06-05 8:05 Jia-Ju Bai
2017-06-05 11:48 ` Trond Myklebust
0 siblings, 1 reply; 3+ messages in thread
From: Jia-Ju Bai @ 2017-06-05 8:05 UTC (permalink / raw)
To: trond.myklebust, anna.schumaker; +Cc: linux-nfs, linux-kernel, Jia-Ju Bai
The driver may sleep under a rcu read lock, and function call path is:
nfs_permission (acquire the lock by rcu_read_lock)
nfs_do_access
nfs_access_add_cache
kmalloc(GFP_KERNEL) --> may sleep
To fix it, "GFP_KERNEL" is replaced with "GFP_ATOMIC".
Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
---
fs/nfs/dir.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 32ccd77..7a074db 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -2333,7 +2333,7 @@ static void nfs_access_add_rbtree(struct inode *inode, struct nfs_access_entry *
void nfs_access_add_cache(struct inode *inode, struct nfs_access_entry *set)
{
- struct nfs_access_entry *cache = kmalloc(sizeof(*cache), GFP_KERNEL);
+ struct nfs_access_entry *cache = kmalloc(sizeof(*cache), GFP_ATOMIC);
if (cache == NULL)
return;
RB_CLEAR_NODE(&cache->rb_node);
--
1.7.9.5
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] fs: nfs: Fix a sleep-in-atomic bug in nfs_access_add_cache
2017-06-05 8:05 [PATCH] fs: nfs: Fix a sleep-in-atomic bug in nfs_access_add_cache Jia-Ju Bai
@ 2017-06-05 11:48 ` Trond Myklebust
2017-06-05 12:36 ` Jia-Ju Bai
0 siblings, 1 reply; 3+ messages in thread
From: Trond Myklebust @ 2017-06-05 11:48 UTC (permalink / raw)
To: baijiaju1990@163.com, anna.schumaker@netapp.com
Cc: linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] fs: nfs: Fix a sleep-in-atomic bug in nfs_access_add_cache
2017-06-05 11:48 ` Trond Myklebust
@ 2017-06-05 12:36 ` Jia-Ju Bai
0 siblings, 0 replies; 3+ messages in thread
From: Jia-Ju Bai @ 2017-06-05 12:36 UTC (permalink / raw)
To: Trond Myklebust
Cc: anna.schumaker@netapp.com, linux-kernel@vger.kernel.org,
linux-nfs@vger.kernel.org
On 06/05/2017 07:48 PM, Trond Myklebust wrote:
> On Mon, 2017-06-05 at 16:05 +0800, Jia-Ju Bai wrote:
>> The driver may sleep under a rcu read lock, and function call path
>> is:
>> nfs_permission (acquire the lock by rcu_read_lock)
>> nfs_do_access
>> nfs_access_add_cache
>> kmalloc(GFP_KERNEL) --> may sleep
>>
>> To fix it, "GFP_KERNEL" is replaced with "GFP_ATOMIC".
>>
>> Signed-off-by: Jia-Ju Bai<baijiaju1990@163.com>
>> ---
>> fs/nfs/dir.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
>> index 32ccd77..7a074db 100644
>> --- a/fs/nfs/dir.c
>> +++ b/fs/nfs/dir.c
>> @@ -2333,7 +2333,7 @@ static void nfs_access_add_rbtree(struct inode
>> *inode, struct nfs_access_entry *
>>
>> void nfs_access_add_cache(struct inode *inode, struct
>> nfs_access_entry *set)
>> {
>> - struct nfs_access_entry *cache = kmalloc(sizeof(*cache),
>> GFP_KERNEL);
>> + struct nfs_access_entry *cache = kmalloc(sizeof(*cache),
>> GFP_ATOMIC);
>> if (cache == NULL)
>> return;
>> RB_CLEAR_NODE(&cache->rb_node);
> The RCU locked codepath will not ever hit nfs_access_add_rbtree(). It
> returns with an error code of -ECHILD after the test of "may_block".
>
> Cheers
> Trond
Yes, I think you are right.
Thanks,
Jia-Ju Bai
^ permalink raw reply [flat|nested] 3+ messages in thread
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2017-06-05 8:05 [PATCH] fs: nfs: Fix a sleep-in-atomic bug in nfs_access_add_cache Jia-Ju Bai
2017-06-05 11:48 ` Trond Myklebust
2017-06-05 12:36 ` Jia-Ju Bai
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