From: Andreas Gruenbacher Subject: Re: [PATCH v14 02/22] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR permission flags Date: Sat, 7 Nov 2015 18:44:28 +0100 Message-ID: <1446918268-858-1-git-send-email-agruenba@redhat.com> References: <1446723580-3747-1-git-send-email-agruenba@redhat.com> <1446723580-3747-3-git-send-email-agruenba@redhat.com> Cc: Andreas Gruenbacher , Alexander Viro , "Theodore Ts'o" , "J. Bruce Fields" , Jeff Layton , Trond Myklebust , Anna Schumaker , Dave Chinner , linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, xfs-VZNHf3L845pBDgjK7y7TUQ@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-cifs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Andreas Dilger Return-path: In-Reply-To: Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-ext4.vger.kernel.org On Fri, Nov 6, 2015 at 9:58 PM, Andreas Dilger wrote: > I thought you proposed adding an enum for these parameters, and possibly > making them a single parameter flag, to make the code in the caller more > readable. No, the result would just be different but not any better; vfs_rename would become messy. I've played with this patch some more, and I find the approach below which splits may_delete into may_delete and may_replace much better. What do you think? Thanks, Andreas ---------- 8< ---------- Richacls distinguish between creating non-directories and directories. To support that, add an isdir parameter to may_create(). When checking inode_permission() for create permission, pass in an additional MAY_CREATE_FILE or MAY_CREATE_DIR mask flag. Add may_replace() to allow checking for delete and create access when replacing an existing file in vfs_rename(). Signed-off-by: Andreas Gruenbacher Reviewed-by: J. Bruce Fields --- fs/namei.c | 49 +++++++++++++++++++++++++++++++++---------------- include/linux/fs.h | 2 ++ 2 files changed, 35 insertions(+), 16 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 224ecf1..4e5dc2f 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -453,7 +453,9 @@ static int sb_permission(struct super_block *sb, struct inode *inode, int mask) * this, letting us set arbitrary permissions for filesystem access without * changing the "normal" UIDs which are used for other things. * - * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. + * MAY_WRITE must be set in @mask whenever MAY_APPEND, MAY_CREATE_FILE, or + * MAY_CREATE_DIR are set. That way, file systems that don't support these + * permissions will check for MAY_WRITE instead. */ int inode_permission(struct inode *inode, int mask) { @@ -2549,7 +2551,8 @@ EXPORT_SYMBOL(__check_sticky); * 10. We don't allow removal of NFS sillyrenamed files; it's handled by * nfs_async_unlink(). */ -static int may_delete(struct inode *dir, struct dentry *victim, bool isdir) +static int may_delete_replace(struct inode *dir, struct dentry *victim, + bool isdir, int mask) { struct inode *inode = d_backing_inode(victim); int error; @@ -2561,7 +2564,7 @@ static int may_delete(struct inode *dir, struct dentry *victim, bool isdir) BUG_ON(victim->d_parent->d_inode != dir); audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE); - error = inode_permission(dir, MAY_WRITE | MAY_EXEC); + error = inode_permission(dir, mask | MAY_WRITE | MAY_EXEC); if (error) return error; if (IS_APPEND(dir)) @@ -2584,6 +2587,18 @@ static int may_delete(struct inode *dir, struct dentry *victim, bool isdir) return 0; } +static int may_delete(struct inode *dir, struct dentry *victim, bool isdir) +{ + return may_delete_replace(dir, victim, isdir, 0); +} + +static int may_replace(struct inode *dir, struct dentry *victim, bool isdir) +{ + int mask = isdir ? MAY_CREATE_DIR : MAY_CREATE_FILE; + + return may_delete_replace(dir, victim, isdir, mask); +} + /* Check whether we can create an object with dentry child in directory * dir. * 1. We can't do it if child already exists (open has special treatment for @@ -2592,14 +2607,16 @@ static int may_delete(struct inode *dir, struct dentry *victim, bool isdir) * 3. We should have write and exec permissions on dir * 4. We can't do it if dir is immutable (done in permission()) */ -static inline int may_create(struct inode *dir, struct dentry *child) +static inline int may_create(struct inode *dir, struct dentry *child, bool isdir) { + int mask = isdir ? MAY_CREATE_DIR : MAY_CREATE_FILE; + audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE); if (child->d_inode) return -EEXIST; if (IS_DEADDIR(dir)) return -ENOENT; - return inode_permission(dir, MAY_WRITE | MAY_EXEC); + return inode_permission(dir, MAY_WRITE | MAY_EXEC | mask); } /* @@ -2649,7 +2666,7 @@ EXPORT_SYMBOL(unlock_rename); int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool want_excl) { - int error = may_create(dir, dentry); + int error = may_create(dir, dentry, false); if (error) return error; @@ -3494,7 +3511,7 @@ EXPORT_SYMBOL(user_path_create); int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) { - int error = may_create(dir, dentry); + int error = may_create(dir, dentry, false); if (error) return error; @@ -3586,7 +3603,7 @@ SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, d int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) { - int error = may_create(dir, dentry); + int error = may_create(dir, dentry, true); unsigned max_links = dir->i_sb->s_max_links; if (error) @@ -3667,7 +3684,7 @@ EXPORT_SYMBOL(dentry_unhash); int vfs_rmdir(struct inode *dir, struct dentry *dentry) { - int error = may_delete(dir, dentry, 1); + int error = may_delete(dir, dentry, true); if (error) return error; @@ -3789,7 +3806,7 @@ SYSCALL_DEFINE1(rmdir, const char __user *, pathname) int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegated_inode) { struct inode *target = dentry->d_inode; - int error = may_delete(dir, dentry, 0); + int error = may_delete(dir, dentry, false); if (error) return error; @@ -3923,7 +3940,7 @@ SYSCALL_DEFINE1(unlink, const char __user *, pathname) int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname) { - int error = may_create(dir, dentry); + int error = may_create(dir, dentry, false); if (error) return error; @@ -4006,7 +4023,7 @@ int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_de if (!inode) return -ENOENT; - error = may_create(dir, new_dentry); + error = may_create(dir, new_dentry, false); if (error) return error; @@ -4199,14 +4216,14 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, return error; if (!target) { - error = may_create(new_dir, new_dentry); + error = may_create(new_dir, new_dentry, is_dir); } else { new_is_dir = d_is_dir(new_dentry); if (!(flags & RENAME_EXCHANGE)) - error = may_delete(new_dir, new_dentry, is_dir); + error = may_replace(new_dir, new_dentry, is_dir); else - error = may_delete(new_dir, new_dentry, new_is_dir); + error = may_replace(new_dir, new_dentry, new_is_dir); } if (error) return error; @@ -4469,7 +4486,7 @@ SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newna int vfs_whiteout(struct inode *dir, struct dentry *dentry) { - int error = may_create(dir, dentry); + int error = may_create(dir, dentry, false); if (error) return error; diff --git a/include/linux/fs.h b/include/linux/fs.h index 4efa435..d6e2330 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -82,6 +82,8 @@ typedef void (dax_iodone_t)(struct buffer_head *bh_map, int uptodate); #define MAY_CHDIR 0x00000040 /* called from RCU mode, don't block */ #define MAY_NOT_BLOCK 0x00000080 +#define MAY_CREATE_FILE 0x00000100 +#define MAY_CREATE_DIR 0x00000200 /* * flags in file.f_mode. Note that FMODE_READ and FMODE_WRITE must correspond -- 2.5.0