Messages in this thread | | | Date | Mon, 05 Jun 2017 20:36:43 +0800 | From | Jia-Ju Bai <> | Subject | Re: [PATCH] fs: nfs: Fix a sleep-in-atomic bug in nfs_access_add_cache |
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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
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