Messages in this thread | | | Subject | Re: [PATCH] fs: nfs: fix a possible sleep-in-atomic-context bug in _pnfs_grab_empty_layout() | From | Jia-Ju Bai <> | Date | Wed, 18 Dec 2019 09:54:31 +0800 |
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On 2019/12/17 22:37, Trond Myklebust wrote: > On Tue, 2019-12-17 at 21:33 +0800, Jia-Ju Bai wrote: >> The filesystem may sleep while holding a spinlock. >> The function call path (from bottom to top) in Linux 4.19 is: >> >> fs/nfs/pnfs.c, 2052: >> pnfs_find_alloc_layout(GFP_KERNEL) in _pnfs_grab_empty_layout >> fs/nfs/pnfs.c, 2051: >> spin_lock in _pnfs_grab_empty_layout >> >> pnfs_find_alloc_layout(GFP_KERNEL) can sleep at runtime. >> >> To fix this possible bug, GFP_KERNEL is replaced with GFP_ATOMIC for >> pnfs_find_alloc_layout(). >> >> This bug is found by a static analysis tool STCheck written by >> myself. >> >> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com> >> --- >> fs/nfs/pnfs.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c >> index cec3070ab577..cfbe170f0651 100644 >> --- a/fs/nfs/pnfs.c >> +++ b/fs/nfs/pnfs.c >> @@ -2138,7 +2138,7 @@ _pnfs_grab_empty_layout(struct inode *ino, >> struct nfs_open_context *ctx) >> struct pnfs_layout_hdr *lo; >> >> spin_lock(&ino->i_lock); >> - lo = pnfs_find_alloc_layout(ino, ctx, GFP_KERNEL); >> + lo = pnfs_find_alloc_layout(ino, ctx, GFP_ATOMIC); >> if (!lo) >> goto out_unlock; >> if (!test_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags)) > I'm not seeing why this is necessary. As far as I can see, > pnfs_find_alloc_layout() will release the ino->i_lock before sleeping. > > False positive? >
Thanks for the reply. You are right, my report is false... I did not check the definition of pnfs_find_alloc_layout(), sorry...
Best wishes, Jia-Ju Bai
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