From: Andreas Dilger Subject: Re: [PATCH v13 02/51] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR permission flags Date: Tue, 3 Nov 2015 19:33:02 -0700 Message-ID: <507E7A63-024B-4EBD-B0C3-4ABE8280440F@dilger.ca> References: <1446563847-14005-1-git-send-email-agruenba@redhat.com> <1446563847-14005-3-git-send-email-agruenba@redhat.com> Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2104\)) Content-Type: multipart/signed; boundary="Apple-Mail=_3E10B02B-D902-4579-9A2C-C87E3793B392"; protocol="application/pgp-signature"; micalg=pgp-sha256 Cc: Theodore Ts'o , "J. Bruce Fields" , Jeff Layton , Trond Myklebust , Anna Schumaker , Dave Chinner , linux-ext4 , XFS Developers , LKML , linux-fsdevel , Linux NFS Mailing List , linux-cifs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linux API To: Andreas Gruenbacher , Alexander Viro Return-path: In-Reply-To: <1446563847-14005-3-git-send-email-agruenba-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Sender: linux-cifs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-ext4.vger.kernel.org --Apple-Mail=_3E10B02B-D902-4579-9A2C-C87E3793B392 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii On Nov 3, 2015, at 8:16 AM, Andreas Gruenbacher = wrote: >=20 > 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. >=20 > To allow checking for delete *and* create access when replacing an = existing > file via vfs_rename(), add a replace parameter to may_delete(). >=20 > Signed-off-by: Andreas Gruenbacher > Reviewed-by: J. Bruce Fields > --- > fs/namei.c | 43 +++++++++++++++++++++++++------------------ > include/linux/fs.h | 2 ++ > 2 files changed, 27 insertions(+), 18 deletions(-) >=20 > diff --git a/fs/namei.c b/fs/namei.c > index 224ecf1..0259392 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) > { > @@ -2549,10 +2551,11 @@ 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(struct inode *dir, struct dentry *victim, > + bool isdir, bool replace) > { > struct inode *inode =3D d_backing_inode(victim); > - int error; > + int error, mask =3D MAY_WRITE | MAY_EXEC; >=20 > if (d_is_negative(victim)) > return -ENOENT; > @@ -2561,7 +2564,9 @@ static int may_delete(struct inode *dir, struct = dentry *victim, bool isdir) > BUG_ON(victim->d_parent->d_inode !=3D dir); > audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE); >=20 > - error =3D inode_permission(dir, MAY_WRITE | MAY_EXEC); > + if (replace) > + mask |=3D isdir ? MAY_CREATE_DIR : MAY_CREATE_FILE; > + error =3D inode_permission(dir, mask); > if (error) > return error; > if (IS_APPEND(dir)) > @@ -2592,14 +2597,16 @@ 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 =3D 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); > } >=20 > /* > @@ -2649,7 +2656,7 @@ EXPORT_SYMBOL(unlock_rename); > int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, > bool want_excl) > { > - int error =3D may_create(dir, dentry); > + int error =3D may_create(dir, dentry, false); > if (error) > return error; >=20 > @@ -3494,7 +3501,7 @@ EXPORT_SYMBOL(user_path_create); >=20 > int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, = dev_t dev) > { > - int error =3D may_create(dir, dentry); > + int error =3D may_create(dir, dentry, false); Passing "true" and "false" from the caller doesn't really make it clear to the reader what the argument is for. Since it isn't possible to check the file mode inside may_create() from dentry->d_inode->i_mode (inode doesn't exist yet) then passing "mode" as an argument would at least make the code more readable. "mode" is available in all of the callers. >=20 > if (error) > return error; > @@ -3586,7 +3593,7 @@ SYSCALL_DEFINE3(mknod, const char __user *, = filename, umode_t, mode, unsigned, d >=20 > int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) > { > - int error =3D may_create(dir, dentry); > + int error =3D may_create(dir, dentry, true); > unsigned max_links =3D dir->i_sb->s_max_links; >=20 > if (error) > @@ -3667,7 +3674,7 @@ EXPORT_SYMBOL(dentry_unhash); >=20 > int vfs_rmdir(struct inode *dir, struct dentry *dentry) > { > - int error =3D may_delete(dir, dentry, 1); > + int error =3D may_delete(dir, dentry, true, false); This is a prime example why passing "true" and "false" as function = arguments is not very useful, and especially prone to bugs when there are two of = them. That said, this is code originally from Al, so he may have a different opinion. Cheers, Andreas >=20 > if (error) > return error; > @@ -3789,7 +3796,7 @@ SYSCALL_DEFINE1(rmdir, const char __user *, = pathname) > int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode = **delegated_inode) > { > struct inode *target =3D dentry->d_inode; > - int error =3D may_delete(dir, dentry, 0); > + int error =3D may_delete(dir, dentry, false, false); >=20 > if (error) > return error; > @@ -3923,7 +3930,7 @@ SYSCALL_DEFINE1(unlink, const char __user *, = pathname) >=20 > int vfs_symlink(struct inode *dir, struct dentry *dentry, const char = *oldname) > { > - int error =3D may_create(dir, dentry); > + int error =3D may_create(dir, dentry, false); >=20 > if (error) > return error; > @@ -4006,7 +4013,7 @@ int vfs_link(struct dentry *old_dentry, struct = inode *dir, struct dentry *new_de > if (!inode) > return -ENOENT; >=20 > - error =3D may_create(dir, new_dentry); > + error =3D may_create(dir, new_dentry, false); > if (error) > return error; >=20 > @@ -4194,19 +4201,19 @@ int vfs_rename(struct inode *old_dir, struct = dentry *old_dentry, > if (source =3D=3D target) > return 0; >=20 > - error =3D may_delete(old_dir, old_dentry, is_dir); > + error =3D may_delete(old_dir, old_dentry, is_dir, false); > if (error) > return error; >=20 > if (!target) { > - error =3D may_create(new_dir, new_dentry); > + error =3D may_create(new_dir, new_dentry, is_dir); > } else { > new_is_dir =3D d_is_dir(new_dentry); >=20 > if (!(flags & RENAME_EXCHANGE)) > - error =3D may_delete(new_dir, new_dentry, = is_dir); > + error =3D may_delete(new_dir, new_dentry, = is_dir, true); > else > - error =3D may_delete(new_dir, new_dentry, = new_is_dir); > + error =3D may_delete(new_dir, new_dentry, = new_is_dir, true); > } > if (error) > return error; > @@ -4469,7 +4476,7 @@ SYSCALL_DEFINE2(rename, const char __user *, = oldname, const char __user *, newna >=20 > int vfs_whiteout(struct inode *dir, struct dentry *dentry) > { > - int error =3D may_create(dir, dentry); > + int error =3D may_create(dir, dentry, false); > if (error) > return error; >=20 > 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 >=20 > /* > * flags in file.f_mode. Note that FMODE_READ and FMODE_WRITE must = correspond > -- > 2.5.0 >=20 Cheers, Andreas --Apple-Mail=_3E10B02B-D902-4579-9A2C-C87E3793B392 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- Comment: GPGTools - http://gpgtools.org iQIVAwUBVjluXnKl2rkXzB/gAQhnew//Xe1j6dVAnqqkD270AcQPLVGrtC4VAGn4 LpMJ3phONjrAEorMAKDqDjD5KIJPm12T8uKHBpIwX/SvNLKwJvTUt54ghXdXRbIC HKAg1FvOSXKIhY8kBugK2WrzRLSv4Af4eBcIpFB+tuzyz4KjyFk16GPCqTW5a6f1 5F64AfiZXBoC3urtTNlsVU7GGy6p6PFmgKH2BJQk5PlhPQSRmUAE22rgCTvHUOX1 MEaAvVdNv79CldjGoc8GC5hrtYAxbFtG2UEveF/nWyUpGYo3+eWzBsbaH4i0DfLU EBvKaK5sPeO+Z+QRwiosebRLA+AYy8iVqjJtB8ROlEdLcqhYrZqyyMypwRxRz9cM LFelz+zuyuNnh29CaG9V1H0+MZMDsNCFLsN7wOrhz6MEWpFrF6Bm74H/zu+d3dAv KS6PaPXtcVkkdXncAMmcSWYXwgF1NukJEBF+433ZXjlBvPzINWp54vebogVNLOJk uRz1FPKv09nXrIouXwxqbaOC1qNQIjwNfiTHfDoqRZYHjVmCX51sKtNRk/oP8u++ QZs2YWhk/FxzDZb8TX2VS0GHF7JsKojI/G2cbvaRp2v2p+iebkMfctHrCKJZz2dE FUlTM5lX0L6nKWgPmFBz+tNmSPkQzMzNsNXbYB/iDPqkr2UJwk5CTgRZ/7wkbBON b5azRC83hBg= =PL0r -----END PGP SIGNATURE----- --Apple-Mail=_3E10B02B-D902-4579-9A2C-C87E3793B392--