Re: [PATCH v14 02/22] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR permission flags
From: Andreas Dilger <hidden>
Date: 2015-11-08 08:18:55
Also in:
linux-api, linux-cifs, linux-fsdevel, linux-nfs, linux-xfs, lkml
Possibly related (same subject, not in this thread)
- 2015-11-07 · Re: [PATCH v14 02/22] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR permission flags · Andreas Gruenbacher <hidden>
- 2015-11-06 · Re: [PATCH v14 02/22] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR permission flags · Andreas Dilger <hidden>
- 2015-11-05 · [PATCH v14 02/22] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR permission flags · Andreas Gruenbacher <agruenba@redhat.com>
On Nov 7, 2015, at 10:44 AM, Andreas Gruenbacher [off-list ref] wrote:
On Fri, Nov 6, 2015 at 9:58 PM, Andreas Dilger [off-list ref] wrote:quoted
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?
This is definitely better than the previous patch. You can add: Reviewed-by: Andreas Dilger <redacted> Cheers, Andreas
quoted hunk
---------- 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 <redacted> Reviewed-by: J. Bruce Fields <redacted> --- 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, dint 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_deif (!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 *, newnaint 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
Cheers, Andreas
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