From: Oleg Drokin <green@linuxhacker.ru>
To: Jeff Layton <jlayton@poochiereds.net>
Cc: "J. Bruce Fields" <bfields@fieldses.org>,
linux-nfs@vger.kernel.org,
"<linux-kernel@vger.kernel.org> Mailing List"
<linux-kernel@vger.kernel.org>
Subject: Re: Files leak from nfsd in 4.7.1-rc1 (and more?)
Date: Wed, 8 Jun 2016 12:10:40 -0400 [thread overview]
Message-ID: <A0A3CAA8-969A-4E12-9532-41DE9D257C74@linuxhacker.ru> (raw)
In-Reply-To: <1465383501.27742.19.camel@poochiereds.net>
On Jun 8, 2016, at 6:58 AM, Jeff Layton wrote:
> A simple way to confirm that might be to convert all of the read locks
> on the st_rwsem to write locks. That will serialize all of the open
> operations and should prevent that particular race from occurring.
>
> If that works, we'd probably want to fix it in a less heavy-handed way,
> but I'd have to think about how best to do that.
So I looked at the call sites for nfs4_get_vfs_file(), how about something like this:
after we grab the fp->fi_lock, we can do test_access(open->op_share_access, stp);
If that returns true - just drop the spinlock and return EAGAIN.
The callsite in nfs4_upgrade_open() would handle that by retesting the access map
again and either coming back in or more likely reusing the now updated stateid
(synchronised by the fi_lock again).
We probably need to convert the whole access map testing there to be under
fi_lock.
Something like:
nfs4_upgrade_open(struct svc_rqst *rqstp, struct nfs4_file *fp, struct svc_fh *cur_fh, struct nfs4_ol_stateid *stp, struct nfsd4_open *open)
{
__be32 status;
unsigned char old_deny_bmap = stp->st_deny_bmap;
again:
+ spin_lock(&fp->fi_lock);
if (!test_access(open->op_share_access, stp)) {
+ spin_unlock(&fp->fi_lock);
+ status = nfs4_get_vfs_file(rqstp, fp, cur_fh, stp, open);
+ if (status == -EAGAIN)
+ goto again;
+ return status;
+ }
/* test and set deny mode */
- spin_lock(&fp->fi_lock);
status = nfs4_file_check_deny(fp, open->op_share_deny);
The call in nfsd4_process_open2() I think cannot hit this condition, right?
probably can add a WARN_ON there? BUG_ON? more sensible approach?
Alternatively we can probably always call nfs4_get_vfs_file() under this spinlock,
just have it drop that for the open and then reobtain (already done), not as transparent I guess.
Or the fi_lock might be converted to say a mutex, so we can sleep with it held and
then we can hold it across whole invocation of nfs4_get_vfs_file() and access testing and stuff.
next prev parent reply other threads:[~2016-06-08 16:10 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-07 15:37 Files leak from nfsd in 4.7.1-rc1 (and more?) Oleg Drokin
2016-06-07 17:10 ` Jeff Layton
2016-06-07 17:30 ` Oleg Drokin
2016-06-07 20:04 ` Jeff Layton
2016-06-07 23:39 ` Oleg Drokin
2016-06-08 0:03 ` Jeff Layton
2016-06-08 0:46 ` Oleg Drokin
2016-06-08 2:22 ` Oleg Drokin
2016-06-08 3:55 ` Oleg Drokin
2016-06-08 10:58 ` Jeff Layton
2016-06-08 14:44 ` Oleg Drokin
2016-06-08 16:10 ` Oleg Drokin [this message]
2016-06-08 17:22 ` Jeff Layton
2016-06-08 17:37 ` Oleg Drokin
2016-06-09 2:55 ` [PATCH] nfsd: Always lock state exclusively Oleg Drokin
2016-06-09 10:13 ` Jeff Layton
2016-06-09 21:01 ` [PATCH] nfsd: Close a race between access checking/setting in nfs4_get_vfs_file Oleg Drokin
2016-06-10 4:18 ` Oleg Drokin
2016-06-10 10:50 ` Jeff Layton
2016-06-10 20:55 ` J . Bruce Fields
2016-06-11 15:41 ` Oleg Drokin
2016-06-12 1:33 ` Jeff Layton
2016-06-12 2:06 ` Oleg Drokin
2016-06-12 2:50 ` Jeff Layton
2016-06-12 3:15 ` Oleg Drokin
2016-06-12 13:13 ` Jeff Layton
2016-06-13 1:26 ` [PATCH v2] nfsd: Always lock state exclusively Oleg Drokin
2016-06-14 15:38 ` J . Bruce Fields
2016-06-14 15:53 ` Oleg Drokin
2016-06-14 18:50 ` J . Bruce Fields
2016-06-14 22:52 ` Jeff Layton
2016-06-14 22:54 ` Oleg Drokin
2016-06-14 22:57 ` Jeff Layton
2016-06-15 3:28 ` [PATCH 0/3] nfsd state handling fixes Oleg Drokin
2016-06-15 3:28 ` [PATCH 1/3] nfsd: Always lock state exclusively Oleg Drokin
2016-06-15 3:28 ` [PATCH 2/3] nfsd: Extend the mutex holding region around in nfsd4_process_open2() Oleg Drokin
2016-06-15 3:28 ` [PATCH 3/3] nfsd: Make init_open_stateid() a bit more whole Oleg Drokin
2016-06-16 1:54 ` [PATCH 0/3] nfsd state handling fixes Oleg Drokin
2016-06-16 2:07 ` J . Bruce Fields
2016-06-14 15:46 ` [PATCH v2] nfsd: Always lock state exclusively J . Bruce Fields
2016-06-14 15:56 ` Oleg Drokin
2016-06-14 18:46 ` J . Bruce Fields
2016-06-15 2:19 ` Oleg Drokin
2016-06-15 13:31 ` J . Bruce Fields
2016-06-09 12:13 ` Files leak from nfsd in 4.7.1-rc1 (and more?) Andrew W Elble
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