vfs: create a generic checking function for FS_IOC_FSSETXATTR

Create a generic checking function for the incoming FS_IOC_FSSETXATTR
fsxattr values so that we can standardize some of the implementation
behaviors.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Jan Kara <jack@suse.cz>

5 files changed, 95 insertions, 48 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index d3d9b4abb09b..3cd66efdb99d 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -375,9 +375,7 @@ static int btrfs_ioctl_fsgetxattr(struct file *file, void __user *arg)
         struct btrfs_inode *binode = BTRFS_I(file_inode(file));
         struct fsxattr fa;
 
-        memset(&fa, 0, sizeof(fa));
-        fa.fsx_xflags = btrfs_inode_flags_to_xflags(binode->flags);
-
+        simple_fill_fsxattr(&fa, btrfs_inode_flags_to_xflags(binode->flags));
         if (copy_to_user(arg, &fa, sizeof(fa)))
                 return -EFAULT;
 
@@ -390,7 +388,7 @@ static int btrfs_ioctl_fssetxattr(struct file *file, void __user *arg)
         struct btrfs_inode *binode = BTRFS_I(inode);
         struct btrfs_root *root = binode->root;
         struct btrfs_trans_handle *trans;
-        struct fsxattr fa;
+        struct fsxattr fa, old_fa;
         unsigned old_flags;
         unsigned old_i_flags;
         int ret = 0;
@@ -401,7 +399,6 @@ static int btrfs_ioctl_fssetxattr(struct file *file, void __user *arg)
         if (btrfs_root_readonly(root))
                 return -EROFS;
 
-        memset(&fa, 0, sizeof(fa));
         if (copy_from_user(&fa, arg, sizeof(fa)))
                 return -EFAULT;
 
@@ -421,13 +418,11 @@ static int btrfs_ioctl_fssetxattr(struct file *file, void __user *arg)
         old_flags = binode->flags;
         old_i_flags = inode->i_flags;
 
-        /* We need the capabilities to change append-only or immutable inode */
-        if (((old_flags & (BTRFS_INODE_APPEND | BTRFS_INODE_IMMUTABLE)) ||
-             (fa.fsx_xflags & (FS_XFLAG_APPEND | FS_XFLAG_IMMUTABLE))) &&
-            !capable(CAP_LINUX_IMMUTABLE)) {
-                ret = -EPERM;
+        simple_fill_fsxattr(&old_fa,
+                            btrfs_inode_flags_to_xflags(binode->flags));
+        ret = vfs_ioc_fssetxattr_check(inode, &old_fa, &fa);
+        if (ret)
                 goto out_unlock;
-        }
 
         if (fa.fsx_xflags & FS_XFLAG_SYNC)
                 binode->flags |= BTRFS_INODE_SYNC;
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 272b6e44191b..1974cb755d09 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -721,6 +721,17 @@ static int ext4_ioctl_check_project(struct inode *inode, struct fsxattr *fa)
         return 0;
 }
 
+static void ext4_fill_fsxattr(struct inode *inode, struct fsxattr *fa)
+{
+        struct ext4_inode_info *ei = EXT4_I(inode);
+
+        simple_fill_fsxattr(fa, ext4_iflags_to_xflags(ei->i_flags &
+                                                      EXT4_FL_USER_VISIBLE));
+
+        if (ext4_has_feature_project(inode->i_sb))
+                fa->fsx_projid = from_kprojid(&init_user_ns, ei->i_projid);
+}
+
 long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
         struct inode *inode = file_inode(filp);
@@ -1089,13 +1100,7 @@ resizefs_out:
         {
                 struct fsxattr fa;
 
-                memset(&fa, 0, sizeof(struct fsxattr));
-                fa.fsx_xflags = ext4_iflags_to_xflags(ei->i_flags & EXT4_FL_USER_VISIBLE);
-
-                if (ext4_has_feature_project(inode->i_sb)) {
-                        fa.fsx_projid = (__u32)from_kprojid(&init_user_ns,
-                                EXT4_I(inode)->i_projid);
-                }
+                ext4_fill_fsxattr(inode, &fa);
 
                 if (copy_to_user((struct fsxattr __user *)arg,
                                  &fa, sizeof(fa)))
@@ -1104,7 +1109,7 @@ resizefs_out:
         }
         case EXT4_IOC_FSSETXATTR:
         {
-                struct fsxattr fa;
+                struct fsxattr fa, old_fa;
                 int err;
 
                 if (copy_from_user(&fa, (struct fsxattr __user *)arg,
@@ -1127,9 +1132,13 @@ resizefs_out:
                         return err;
 
                 inode_lock(inode);
+                ext4_fill_fsxattr(inode, &old_fa);
                 err = ext4_ioctl_check_project(inode, &fa);
                 if (err)
                         goto out;
+                err = vfs_ioc_fssetxattr_check(inode, &old_fa, &fa);
+                if (err)
+                        goto out;
                 flags = (ei->i_flags & ~EXT4_FL_XFLAG_VISIBLE) |
                          (flags & EXT4_FL_XFLAG_VISIBLE);
                 err = ext4_ioctl_setflags(inode, flags);
diff --git a/fs/inode.c b/fs/inode.c
index 8072a09fd0b9..ba2bafa22885 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2194,3 +2194,26 @@ int vfs_ioc_setflags_prepare(struct inode *inode, unsigned int oldflags,
         return 0;
 }
 EXPORT_SYMBOL(vfs_ioc_setflags_prepare);
+
+/*
+ * Generic function to check FS_IOC_FSSETXATTR values and reject any invalid
+ * configurations.
+ *
+ * Note: the caller should be holding i_mutex, or else be sure that they have
+ * exclusive access to the inode structure.
+ */
+int vfs_ioc_fssetxattr_check(struct inode *inode, const struct fsxattr *old_fa,
+                             struct fsxattr *fa)
+{
+        /*
+         * Can't modify an immutable/append-only file unless we have
+         * appropriate permission.
+         */
+        if ((old_fa->fsx_xflags ^ fa->fsx_xflags) &
+                        (FS_XFLAG_IMMUTABLE | FS_XFLAG_APPEND) &&
+            !capable(CAP_LINUX_IMMUTABLE))
+                return -EPERM;
+
+        return 0;
+}
+EXPORT_SYMBOL(vfs_ioc_fssetxattr_check);
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index d7dfc13f30f5..458a7043b4d2 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -879,37 +879,44 @@ xfs_di2lxflags(
         return flags;
 }
 
-STATIC int
-xfs_ioc_fsgetxattr(
-        xfs_inode_t             *ip,
-        int                     attr,
-        void                    __user *arg)
+static void
+xfs_fill_fsxattr(
+        struct xfs_inode        *ip,
+        bool                    attr,
+        struct fsxattr          *fa)
 {
-        struct fsxattr          fa;
-
-        memset(&fa, 0, sizeof(struct fsxattr));
-
-        xfs_ilock(ip, XFS_ILOCK_SHARED);
-        fa.fsx_xflags = xfs_ip2xflags(ip);
-        fa.fsx_extsize = ip->i_d.di_extsize << ip->i_mount->m_sb.sb_blocklog;
-        fa.fsx_cowextsize = ip->i_d.di_cowextsize <<
+        simple_fill_fsxattr(fa, xfs_ip2xflags(ip));
+        fa->fsx_extsize = ip->i_d.di_extsize << ip->i_mount->m_sb.sb_blocklog;
+        fa->fsx_cowextsize = ip->i_d.di_cowextsize <<
                         ip->i_mount->m_sb.sb_blocklog;
-        fa.fsx_projid = xfs_get_projid(ip);
+        fa->fsx_projid = xfs_get_projid(ip);
 
         if (attr) {
                 if (ip->i_afp) {
                         if (ip->i_afp->if_flags & XFS_IFEXTENTS)
-                                fa.fsx_nextents = xfs_iext_count(ip->i_afp);
+                                fa->fsx_nextents = xfs_iext_count(ip->i_afp);
                         else
-                                fa.fsx_nextents = ip->i_d.di_anextents;
+                                fa->fsx_nextents = ip->i_d.di_anextents;
                 } else
-                        fa.fsx_nextents = 0;
+                        fa->fsx_nextents = 0;
         } else {
                 if (ip->i_df.if_flags & XFS_IFEXTENTS)
-                        fa.fsx_nextents = xfs_iext_count(&ip->i_df);
+                        fa->fsx_nextents = xfs_iext_count(&ip->i_df);
                 else
-                        fa.fsx_nextents = ip->i_d.di_nextents;
+                        fa->fsx_nextents = ip->i_d.di_nextents;
         }
+}
+
+STATIC int
+xfs_ioc_fsgetxattr(
+        xfs_inode_t             *ip,
+        int                     attr,
+        void                    __user *arg)
+{
+        struct fsxattr          fa;
+
+        xfs_ilock(ip, XFS_ILOCK_SHARED);
+        xfs_fill_fsxattr(ip, attr, &fa);
         xfs_iunlock(ip, XFS_ILOCK_SHARED);
 
         if (copy_to_user(arg, &fa, sizeof(fa)))
@@ -1035,15 +1042,6 @@ xfs_ioctl_setattr_xflags(
         if ((fa->fsx_xflags & FS_XFLAG_DAX) && xfs_is_reflink_inode(ip))
                 return -EINVAL;
 
-        /*
-         * Can't modify an immutable/append-only file unless
-         * we have appropriate permission.
-         */
-        if (((ip->i_d.di_flags & (XFS_DIFLAG_IMMUTABLE | XFS_DIFLAG_APPEND)) ||
-             (fa->fsx_xflags & (FS_XFLAG_IMMUTABLE | FS_XFLAG_APPEND))) &&
-            !capable(CAP_LINUX_IMMUTABLE))
-                return -EPERM;
-
         /* diflags2 only valid for v3 inodes. */
         di_flags2 = xfs_flags2diflags2(ip, fa->fsx_xflags);
         if (di_flags2 && ip->i_d.di_version < 3)
@@ -1323,6 +1321,7 @@ xfs_ioctl_setattr(
         xfs_inode_t             *ip,
         struct fsxattr          *fa)
 {
+        struct fsxattr          old_fa;
         struct xfs_mount        *mp = ip->i_mount;
         struct xfs_trans        *tp;
         struct xfs_dquot        *udqp = NULL;
@@ -1370,7 +1369,6 @@ xfs_ioctl_setattr(
                 goto error_free_dquots;
         }
 
-
         if (XFS_IS_QUOTA_RUNNING(mp) && XFS_IS_PQUOTA_ON(mp) &&
             xfs_get_projid(ip) != fa->fsx_projid) {
                 code = xfs_qm_vop_chown_reserve(tp, ip, udqp, NULL, pdqp,
@@ -1379,6 +1377,11 @@ xfs_ioctl_setattr(
                         goto error_trans_cancel;
         }
 
+        xfs_fill_fsxattr(ip, false, &old_fa);
+        code = vfs_ioc_fssetxattr_check(VFS_I(ip), &old_fa, fa);
+        if (code)
+                goto error_trans_cancel;
+
         code = xfs_ioctl_setattr_check_extsize(ip, fa);
         if (code)
                 goto error_trans_cancel;
@@ -1489,6 +1492,7 @@ xfs_ioc_setxflags(
 {
         struct xfs_trans        *tp;
         struct fsxattr          fa;
+        struct fsxattr          old_fa;
         unsigned int            flags;
         int                     join_flags = 0;
         int                     error;
@@ -1524,6 +1528,13 @@ xfs_ioc_setxflags(
                 goto out_drop_write;
         }
 
+        xfs_fill_fsxattr(ip, false, &old_fa);
+        error = vfs_ioc_fssetxattr_check(VFS_I(ip), &old_fa, &fa);
+        if (error) {
+                xfs_trans_cancel(tp);
+                goto out_drop_write;
+        }
+
         error = xfs_ioctl_setattr_xflags(tp, ip, &fa);
         if (error) {
                 xfs_trans_cancel(tp);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 41d5175ffdd7..36f9691d7046 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3549,4 +3549,13 @@ static inline struct sock *io_uring_get_socket(struct file *file)
 int vfs_ioc_setflags_prepare(struct inode *inode, unsigned int oldflags,
                              unsigned int flags);
 
+int vfs_ioc_fssetxattr_check(struct inode *inode, const struct fsxattr *old_fa,
+                             struct fsxattr *fa);
+
+static inline void simple_fill_fsxattr(struct fsxattr *fa, __u32 xflags)
+{
+        memset(fa, 0, sizeof(*fa));
+        fa->fsx_xflags = xflags;
+}
+
 #endif /* _LINUX_FS_H */