Re: [PATCH] nfsd: set acl_access/acl_default after getting successful

["zhangjian (CG)" <zhangjian496@huawei.com>]

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@huaweicloud.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;
>   	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;
>   	}
>   	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;
>   		}
> -		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;