From:   trondmy@kernel.org
To:     Anna Schumaker <Anna.Schumaker@netapp.com>
Cc:     linux-nfs@vger.kernel.org
Subject: [PATCH v2 8/8] NFSv4: Add an ioctl to allow retrieval of the NFS raw ACCESS mask
Date:   Mon, 27 Dec 2021 14:05:04 -0500
Message-Id: <20211227190504.309612-9-trondmy@kernel.org>
In-Reply-To: <20211227190504.309612-8-trondmy@kernel.org>
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From: Trond Myklebust <trond.myklebust@hammerspace.com>

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfs/dir.c             | 47 ++++++++++++++++++++++++----------------
 fs/nfs/internal.h        |  2 ++
 fs/nfs/nfs4file.c        | 39 +++++++++++++++++++++++++++++++++
 include/uapi/linux/nfs.h | 11 ++++++++++
 4 files changed, 80 insertions(+), 19 deletions(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 10a6484c59d3..e8e6a2f7de1f 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -2907,36 +2907,30 @@ void nfs_access_set_mask(struct nfs_access_entry *entry, u32 access_result)
 }
 EXPORT_SYMBOL_GPL(nfs_access_set_mask);
 
-static int nfs_do_access(struct inode *inode, const struct cred *cred, int mask)
+int nfs_get_access(struct inode *inode, const struct cred *cred,
+		   struct nfs_access_entry *cache, bool may_block)
 {
-	struct nfs_access_entry cache;
-	bool may_block = (mask & MAY_NOT_BLOCK) == 0;
-	int cache_mask = -1;
 	int status;
 
-	trace_nfs_access_enter(inode);
-
-	status = nfs_access_get_cached(inode, cred, &cache.mask, may_block);
+	status = nfs_access_get_cached(inode, cred, &cache->mask, may_block);
 	if (status == 0)
-		goto out_cached;
+		return 0;
 
-	status = -ECHILD;
 	if (!may_block)
-		goto out;
-
+		return -ECHILD;
 	/*
 	 * Determine which access bits we want to ask for...
 	 */
-	cache.mask = NFS_ACCESS_READ | NFS_ACCESS_MODIFY | NFS_ACCESS_EXTEND;
+	cache->mask = NFS_ACCESS_READ | NFS_ACCESS_MODIFY | NFS_ACCESS_EXTEND;
 	if (nfs_server_capable(inode, NFS_CAP_XATTR)) {
-		cache.mask |= NFS_ACCESS_XAREAD | NFS_ACCESS_XAWRITE |
+		cache->mask |= NFS_ACCESS_XAREAD | NFS_ACCESS_XAWRITE |
 		    NFS_ACCESS_XALIST;
 	}
 	if (S_ISDIR(inode->i_mode))
-		cache.mask |= NFS_ACCESS_DELETE | NFS_ACCESS_LOOKUP;
+		cache->mask |= NFS_ACCESS_DELETE | NFS_ACCESS_LOOKUP;
 	else
-		cache.mask |= NFS_ACCESS_EXECUTE;
-	status = NFS_PROTO(inode)->access(inode, &cache, cred);
+		cache->mask |= NFS_ACCESS_EXECUTE;
+	status = NFS_PROTO(inode)->access(inode, cache, cred);
 	if (status != 0) {
 		if (status == -ESTALE) {
 			if (!S_ISDIR(inode->i_mode))
@@ -2944,10 +2938,25 @@ static int nfs_do_access(struct inode *inode, const struct cred *cred, int mask)
 			else
 				nfs_zap_caches(inode);
 		}
-		goto out;
+		return status;
 	}
-	nfs_access_add_cache(inode, &cache, cred);
-out_cached:
+	nfs_access_add_cache(inode, cache, cred);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nfs_get_access);
+
+static int nfs_do_access(struct inode *inode, const struct cred *cred, int mask)
+{
+	struct nfs_access_entry cache;
+	bool may_block = (mask & MAY_NOT_BLOCK) == 0;
+	int cache_mask = -1;
+	int status;
+
+	trace_nfs_access_enter(inode);
+
+	status = nfs_get_access(inode, cred, &cache, may_block);
+	if (status < 0)
+		goto out;
 	cache_mask = nfs_access_calc_mask(cache.mask, inode->i_mode);
 	if ((mask & ~cache_mask & (MAY_READ | MAY_WRITE | MAY_EXEC)) != 0)
 		status = -EACCES;
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 9602a886f0f0..9b8fd2247533 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -392,6 +392,8 @@ int nfs_mknod(struct user_namespace *, struct inode *, struct dentry *, umode_t,
 	      dev_t);
 int nfs_rename(struct user_namespace *, struct inode *, struct dentry *,
 	       struct inode *, struct dentry *, unsigned int);
+int nfs_get_access(struct inode *inode, const struct cred *cred,
+		   struct nfs_access_entry *cache, bool may_block);
 
 /* file.c */
 int nfs_file_fsync(struct file *file, loff_t start, loff_t end, int datasync);
diff --git a/fs/nfs/nfs4file.c b/fs/nfs/nfs4file.c
index 494ebc7cd1c0..ccf70d26c5c4 100644
--- a/fs/nfs/nfs4file.c
+++ b/fs/nfs/nfs4file.c
@@ -611,6 +611,42 @@ static long nfs4_ioctl_file_statx_set(struct file *dst_file,
 	return ret;
 }
 
+static long
+nfs4_ioctl_file_access_get(struct file *file,
+			   struct nfs_ioctl_nfs4_access __user *uarg)
+{
+	struct inode *inode = file_inode(file);
+	struct nfs_access_entry cache;
+	__u64 ac_flags;
+	const struct cred *old_cred;
+	struct cred *override_cred;
+	long ret;
+
+	if (!NFS_PROTO(inode)->access)
+		return -ENOTSUPP;
+
+	if (get_user(ac_flags, &uarg->ac_flags))
+		return -EFAULT;
+
+	override_cred = prepare_creds();
+	if (!override_cred)
+		return -ENOMEM;
+
+	if (!(ac_flags & NFS_AC_FLAG_EACCESS)) {
+		override_cred->fsuid = override_cred->uid;
+		override_cred->fsgid = override_cred->gid;
+	}
+	old_cred = override_creds(override_cred);
+
+	ret = nfs_get_access(inode, override_cred, &cache, true);
+	if (!ret && unlikely(put_user(cache.mask, &uarg->ac_mask) != 0))
+		ret = -EFAULT;
+
+	revert_creds(old_cred);
+	put_cred(override_cred);
+	return ret;
+}
+
 static long nfs4_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	void __user *argp = (void __user *)arg;
@@ -623,6 +659,9 @@ static long nfs4_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case NFS_IOC_FILE_STATX_SET:
 		ret = nfs4_ioctl_file_statx_set(file, argp);
 		break;
+	case NFS_IOC_FILE_ACCESS_GET:
+		ret = nfs4_ioctl_file_access_get(file, argp);
+		break;
 	default:
 		ret = -ENOIOCTLCMD;
 	}
diff --git a/include/uapi/linux/nfs.h b/include/uapi/linux/nfs.h
index df87da39bc43..b1e50f14db18 100644
--- a/include/uapi/linux/nfs.h
+++ b/include/uapi/linux/nfs.h
@@ -41,6 +41,8 @@
 #define NFS_IOC_FILE_STATX_GET	_IOR('N', 2, struct nfs_ioctl_nfs4_statx)
 #define NFS_IOC_FILE_STATX_SET	_IOW('N', 3, struct nfs_ioctl_nfs4_statx)
 
+#define NFS_IOC_FILE_ACCESS_GET	_IOR('N', 4, struct nfs_ioctl_nfs4_access)
+
 /* Options for struct nfs_ioctl_nfs4_statx */
 #define NFS_FA_OPTIONS_SYNC_AS_STAT			0x0000
 #define NFS_FA_OPTIONS_FORCE_SYNC			0x2000 /* See statx */
@@ -125,6 +127,15 @@ struct nfs_ioctl_nfs4_statx {
 	__u64 		fa_padding[4];
 };
 
+struct nfs_ioctl_nfs4_access {
+	/* input */
+	__u64		ac_flags;		/* operation flags */
+	/* output */
+	__u64		ac_mask;		/* NFS raw ACCESS reply mask */
+};
+
+#define NFS_AC_FLAG_EACCESS (1UL << 0)
+
 /*
  * NFS stats. The good thing with these values is that NFSv3 errors are
  * a superset of NFSv2 errors (with the exception of NFSERR_WFLUSH which
-- 
2.33.1