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Message-ID: <CAM5tNy4rYLWSuO_KrgXJrHV+DPhOoZGZAdWLZsW35u3qWuMSvg@mail.gmail.com>
Date: Wed, 27 Nov 2024 19:14:57 -0800
From: Rick Macklem <rick.macklem@...il.com>
To: "zhangjian (CG)" <zhangjian496@...wei.com>
Cc: Li Lingfeng <lilingfeng@...weicloud.com>, chuck.lever@...cle.com, jlayton@...nel.org,
neilb@...e.de, okorniev@...hat.com, kolga@...app.com, Dai.Ngo@...cle.com,
tom@...pey.com, Trond.Myklebust@...app.com, linux-nfs@...r.kernel.org,
linux-kernel@...r.kernel.org, yukuai1@...weicloud.com, houtao1@...wei.com,
yi.zhang@...wei.com, yangerkun@...wei.com, lilingfeng3@...wei.com
Subject: Re: [PATCH] nfsd: set acl_access/acl_default after getting successful
On Wed, Nov 27, 2024 at 5:18 PM zhangjian (CG) <zhangjian496@...wei.com> wrote:
>
> there is one case when disk error cause get_inode_acl(inode,
> ACL_TYPE_DEFAULT) return EIO,
> resp->acl_access will not be null. posix_acl_release(resp->acl_default)
> will trigger this warning.
>
>
> > If getting acl_default fails, acl_access and acl_default will be released
> > simultaneously. However, acl_access will still retain a pointer pointing
> > to the released posix_acl, which will trigger a WARNING in
> > nfs3svc_release_getacl like this:
> >
> > ------------[ cut here ]------------
> > refcount_t: underflow; use-after-free.
> > WARNING: CPU: 26 PID: 3199 at lib/refcount.c:28
> > refcount_warn_saturate+0xb5/0x170
> > Modules linked in:
> > CPU: 26 UID: 0 PID: 3199 Comm: nfsd Not tainted
> > 6.12.0-rc6-00079-g04ae226af01f-dirty #8
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> > 1.16.1-2.fc37 04/01/2014
> > RIP: 0010:refcount_warn_saturate+0xb5/0x170
> > Code: cc cc 0f b6 1d b3 20 a5 03 80 fb 01 0f 87 65 48 d8 00 83 e3 01 75
> > e4 48 c7 c7 c0 3b 9b 85 c6 05 97 20 a5 03 01 e8 fb 3e 30 ff <0f> 0b eb
> > cd 0f b6 1d 8a3
> > RSP: 0018:ffffc90008637cd8 EFLAGS: 00010282
> > RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff83904fde
> > RDX: dffffc0000000000 RSI: 0000000000000008 RDI: ffff88871ed36380
> > RBP: ffff888158beeb40 R08: 0000000000000001 R09: fffff520010c6f56
> > R10: ffffc90008637ab7 R11: 0000000000000001 R12: 0000000000000001
> > R13: ffff888140e77400 R14: ffff888140e77408 R15: ffffffff858b42c0
> > FS: 0000000000000000(0000) GS:ffff88871ed00000(0000)
> > knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000562384d32158 CR3: 000000055cc6a000 CR4: 00000000000006f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> > <TASK>
> > ? refcount_warn_saturate+0xb5/0x170
> > ? __warn+0xa5/0x140
> > ? refcount_warn_saturate+0xb5/0x170
> > ? report_bug+0x1b1/0x1e0
> > ? handle_bug+0x53/0xa0
> > ? exc_invalid_op+0x17/0x40
> > ? asm_exc_invalid_op+0x1a/0x20
> > ? tick_nohz_tick_stopped+0x1e/0x40
> > ? refcount_warn_saturate+0xb5/0x170
> > ? refcount_warn_saturate+0xb5/0x170
> > nfs3svc_release_getacl+0xc9/0xe0
> > svc_process_common+0x5db/0xb60
> > ? __pfx_svc_process_common+0x10/0x10
> > ? __rcu_read_unlock+0x69/0xa0
> > ? __pfx_nfsd_dispatch+0x10/0x10
> > ? svc_xprt_received+0xa1/0x120
> > ? xdr_init_decode+0x11d/0x190
> > svc_process+0x2a7/0x330
> > svc_handle_xprt+0x69d/0x940
> > svc_recv+0x180/0x2d0
> > nfsd+0x168/0x200
> > ? __pfx_nfsd+0x10/0x10
> > kthread+0x1a2/0x1e0
> > ? kthread+0xf4/0x1e0
> > ? __pfx_kthread+0x10/0x10
> > ret_from_fork+0x34/0x60
> > ? __pfx_kthread+0x10/0x10
> > ret_from_fork_asm+0x1a/0x30
> > </TASK>
> > Kernel panic - not syncing: kernel: panic_on_warn set ...
> >
> > Clear acl_access/acl_default first and set both of them only when both
> > ACLs are successfully obtained.
> >
> > Fixes: a257cdd0e217 ("[PATCH] NFSD: Add server support for NFSv3 ACLs.")
> > Signed-off-by: Li Lingfeng <lilingfeng@...weicloud.com>
> > ---
> > fs/nfsd/nfs3acl.c | 14 ++++++++------
> > 1 file changed, 8 insertions(+), 6 deletions(-)
> >
> > diff --git a/fs/nfsd/nfs3acl.c b/fs/nfsd/nfs3acl.c
> > index 5e34e98db969..17579a032a5b 100644
> > --- a/fs/nfsd/nfs3acl.c
> > +++ b/fs/nfsd/nfs3acl.c
> > @@ -29,10 +29,12 @@ static __be32 nfsd3_proc_getacl(struct svc_rqst *rqstp)
> > {
> > struct nfsd3_getaclargs *argp = rqstp->rq_argp;
> > struct nfsd3_getaclres *resp = rqstp->rq_resp;
> > - struct posix_acl *acl;
> > + struct posix_acl *acl = NULL, *dacl = NULL;
> > struct inode *inode;
> > svc_fh *fh;
> >
> > + resp->acl_access = NULL;
> > + resp->acl_default = NULL;
(A) These two lines fix the bug, without other changes needed, I think...
> > fh = fh_copy(&resp->fh, &argp->fh);
> > resp->status = fh_verify(rqstp, &resp->fh, 0, NFSD_MAY_NOP);
> > if (resp->status != nfs_ok)
> > @@ -56,19 +58,19 @@ static __be32 nfsd3_proc_getacl(struct svc_rqst *rqstp)
> > resp->status = nfserrno(PTR_ERR(acl));
> > goto fail;
> > }
> > - resp->acl_access = acl;
Because you deleted this line...
> > }
> > if (resp->mask & (NFS_DFACL|NFS_DFACLCNT)) {
> > /* Check how Solaris handles requests for the Default ACL
> > of a non-directory! */
> > - acl = get_inode_acl(inode, ACL_TYPE_DEFAULT);
> > - if (IS_ERR(acl)) {
> > - resp->status = nfserrno(PTR_ERR(acl));
> > + dacl = get_inode_acl(inode, ACL_TYPE_DEFAULT);
> > + if (IS_ERR(dacl)) {
> > + resp->status = nfserrno(PTR_ERR(dacl));
> > goto fail;
The goto fail here will not release the access acl, if I read the code
correctly.
> > }
> > - resp->acl_default = acl;
> > }
> >
> > + resp->acl_access = acl;
> > + resp->acl_default = dacl;
> > /* resp->acl_{access,default} are released in nfs3svc_release_getacl. */
> > out:
> > return rpc_success;
>
Actually, all that is needed to fix the bug is adding the two lines
that initialize
them both NUL, I think.. I marked that change (A) above.
rick
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