On Wed, Nov 27, 2024 at 7:14 PM Rick Macklem <rick.macklem@xxxxxxxxx> wrote:
>
> On Wed, Nov 27, 2024 at 5:18 PM zhangjian (CG) <zhangjian496@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx>
> > > ---
> > > 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...
Oops, I was wrong w.r.t. this. These two lines need to be repeated after the
posix_acl_relase() calls under "fail:".
> > > 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.
Nope, I was wrong w.r.t. this part. You either need to set
resp->acl_access = acl;
resp->acl_default = dacl;
after the posix_acl_relase() calls or switch to using the local
acl and dacl variables for these posix_acl_release calls and stick
with what you did above w.r.t. resp->acl_access and resp->acl_default.
Anyhow, I think the case I noted above where get_inode_acl(inode,
ACL_TYPE_DEFAULT)
fails will not release acl with your patch.
rick
>
> rick
