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Date: Thu, 03 Jul 2008 11:11:27 +0100
From: Steven Whitehouse <swhiteho@...hat.com>
To: Miklos Szeredi <miklos@...redi.hu>
Cc: akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
linux-fsdevel@...r.kernel.org, hch@...radead.org
Subject: Re: [patch v2] gfs2: don't call permission()
Hi,
Now in the GFS2 -nmw git tree. Thanks,
Steve.
On Wed, 2008-07-02 at 21:12 +0200, Miklos Szeredi wrote:
> This is the updated version, with the promised renames:
>
> gfs2_do_permission -> gfs2_permission
> gfs2_permission -> gfs2_iop_permission
>
> Thanks,
> Miklos
>
> ----
> From: Miklos Szeredi <mszeredi@...e.cz>
>
> GFS2 calls permission() to verify permissions after locks on the files
> have been taken.
>
> For this it's sufficient to call gfs2_permission() instead. This
> results in the following changes:
>
> - IS_RDONLY() check is not performed
> - IS_IMMUTABLE() check is not performed
> - devcgroup_inode_permission() is not called
> - security_inode_permission() is not called
>
> IS_RDONLY() should be unnecessary anyway, as the per-mount read-only
> flag should provide protection against read-only remounts during
> operations. do_gfs2_set_flags() has been fixed to perform
> mnt_want_write()/mnt_drop_write() to protect against remounting
> read-only.
>
> IS_IMMUTABLE has been added to gfs2_permission()
>
> Repeating the security checks seems to be pointless, as they don't
> normally change, and if they do, it's independent of the filesystem
> state.
>
> Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
> ---
> fs/gfs2/inode.c | 6 +++---
> fs/gfs2/inode.h | 1 +
> fs/gfs2/ops_file.c | 11 +++++++++--
> fs/gfs2/ops_inode.c | 25 +++++++++++++++++--------
> 4 files changed, 30 insertions(+), 13 deletions(-)
>
> Index: linux-2.6/fs/gfs2/inode.c
> ===================================================================
> --- linux-2.6.orig/fs/gfs2/inode.c 2008-07-01 18:11:32.000000000 +0200
> +++ linux-2.6/fs/gfs2/inode.c 2008-07-01 19:15:59.000000000 +0200
> @@ -504,7 +504,7 @@ struct inode *gfs2_lookupi(struct inode
> }
>
> if (!is_root) {
> - error = permission(dir, MAY_EXEC, NULL);
> + error = gfs2_permission(dir, MAY_EXEC);
> if (error)
> goto out;
> }
> @@ -667,7 +667,7 @@ static int create_ok(struct gfs2_inode *
> {
> int error;
>
> - error = permission(&dip->i_inode, MAY_WRITE | MAY_EXEC, NULL);
> + error = gfs2_permission(&dip->i_inode, MAY_WRITE | MAY_EXEC);
> if (error)
> return error;
>
> @@ -1134,7 +1134,7 @@ int gfs2_unlink_ok(struct gfs2_inode *di
> if (IS_APPEND(&dip->i_inode))
> return -EPERM;
>
> - error = permission(&dip->i_inode, MAY_WRITE | MAY_EXEC, NULL);
> + error = gfs2_permission(&dip->i_inode, MAY_WRITE | MAY_EXEC);
> if (error)
> return error;
>
> Index: linux-2.6/fs/gfs2/inode.h
> ===================================================================
> --- linux-2.6.orig/fs/gfs2/inode.h 2008-07-01 18:11:32.000000000 +0200
> +++ linux-2.6/fs/gfs2/inode.h 2008-07-01 19:15:59.000000000 +0200
> @@ -91,6 +91,7 @@ int gfs2_rmdiri(struct gfs2_inode *dip,
> struct gfs2_inode *ip);
> int gfs2_unlink_ok(struct gfs2_inode *dip, const struct qstr *name,
> const struct gfs2_inode *ip);
> +int gfs2_permission(struct inode *inode, int mask);
> int gfs2_ok_to_move(struct gfs2_inode *this, struct gfs2_inode *to);
> int gfs2_readlinki(struct gfs2_inode *ip, char **buf, unsigned int *len);
> int gfs2_glock_nq_atime(struct gfs2_holder *gh);
> Index: linux-2.6/fs/gfs2/ops_file.c
> ===================================================================
> --- linux-2.6.orig/fs/gfs2/ops_file.c 2008-07-01 18:11:32.000000000 +0200
> +++ linux-2.6/fs/gfs2/ops_file.c 2008-07-01 19:15:59.000000000 +0200
> @@ -15,6 +15,7 @@
> #include <linux/uio.h>
> #include <linux/blkdev.h>
> #include <linux/mm.h>
> +#include <linux/mount.h>
> #include <linux/fs.h>
> #include <linux/gfs2_ondisk.h>
> #include <linux/ext2_fs.h>
> @@ -220,10 +221,14 @@ static int do_gfs2_set_flags(struct file
> int error;
> u32 new_flags, flags;
>
> - error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
> + error = mnt_want_write(filp->f_path.mnt);
> if (error)
> return error;
>
> + error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
> + if (error)
> + goto out_drop_write;
> +
> flags = ip->i_di.di_flags;
> new_flags = (flags & ~mask) | (reqflags & mask);
> if ((new_flags ^ flags) == 0)
> @@ -242,7 +247,7 @@ static int do_gfs2_set_flags(struct file
> !capable(CAP_LINUX_IMMUTABLE))
> goto out;
> if (!IS_IMMUTABLE(inode)) {
> - error = permission(inode, MAY_WRITE, NULL);
> + error = gfs2_permission(inode, MAY_WRITE);
> if (error)
> goto out;
> }
> @@ -272,6 +277,8 @@ out_trans_end:
> gfs2_trans_end(sdp);
> out:
> gfs2_glock_dq_uninit(&gh);
> +out_drop_write:
> + mnt_drop_write(filp->f_path.mnt);
> return error;
> }
>
> Index: linux-2.6/fs/gfs2/ops_inode.c
> ===================================================================
> --- linux-2.6.orig/fs/gfs2/ops_inode.c 2008-07-01 18:11:32.000000000 +0200
> +++ linux-2.6/fs/gfs2/ops_inode.c 2008-07-01 19:15:59.000000000 +0200
> @@ -163,7 +163,7 @@ static int gfs2_link(struct dentry *old_
> if (error)
> goto out;
>
> - error = permission(dir, MAY_WRITE | MAY_EXEC, NULL);
> + error = gfs2_permission(dir, MAY_WRITE | MAY_EXEC);
> if (error)
> goto out_gunlock;
>
> @@ -669,7 +669,7 @@ static int gfs2_rename(struct inode *odi
> }
> }
> } else {
> - error = permission(ndir, MAY_WRITE | MAY_EXEC, NULL);
> + error = gfs2_permission(ndir, MAY_WRITE | MAY_EXEC);
> if (error)
> goto out_gunlock;
>
> @@ -704,7 +704,7 @@ static int gfs2_rename(struct inode *odi
> /* Check out the dir to be renamed */
>
> if (dir_rename) {
> - error = permission(odentry->d_inode, MAY_WRITE, NULL);
> + error = gfs2_permission(odentry->d_inode, MAY_WRITE);
> if (error)
> goto out_gunlock;
> }
> @@ -891,7 +891,7 @@ static void *gfs2_follow_link(struct den
> * Returns: errno
> */
>
> -static int gfs2_permission(struct inode *inode, int mask, struct nameidata *nd)
> +int gfs2_permission(struct inode *inode, int mask)
> {
> struct gfs2_inode *ip = GFS2_I(inode);
> struct gfs2_holder i_gh;
> @@ -905,13 +905,22 @@ static int gfs2_permission(struct inode
> unlock = 1;
> }
>
> - error = generic_permission(inode, mask, gfs2_check_acl);
> + if ((mask & MAY_WRITE) && IS_IMMUTABLE(inode))
> + error = -EACCES;
> + else
> + error = generic_permission(inode, mask, gfs2_check_acl);
> if (unlock)
> gfs2_glock_dq_uninit(&i_gh);
>
> return error;
> }
>
> +static int gfs2_iop_permission(struct inode *inode, int mask,
> + struct nameidata *nd)
> +{
> + return gfs2_permission(inode, mask);
> +}
> +
> static int setattr_size(struct inode *inode, struct iattr *attr)
> {
> struct gfs2_inode *ip = GFS2_I(inode);
> @@ -1141,7 +1150,7 @@ static int gfs2_removexattr(struct dentr
> }
>
> const struct inode_operations gfs2_file_iops = {
> - .permission = gfs2_permission,
> + .permission = gfs2_iop_permission,
> .setattr = gfs2_setattr,
> .getattr = gfs2_getattr,
> .setxattr = gfs2_setxattr,
> @@ -1160,7 +1169,7 @@ const struct inode_operations gfs2_dir_i
> .rmdir = gfs2_rmdir,
> .mknod = gfs2_mknod,
> .rename = gfs2_rename,
> - .permission = gfs2_permission,
> + .permission = gfs2_iop_permission,
> .setattr = gfs2_setattr,
> .getattr = gfs2_getattr,
> .setxattr = gfs2_setxattr,
> @@ -1172,7 +1181,7 @@ const struct inode_operations gfs2_dir_i
> const struct inode_operations gfs2_symlink_iops = {
> .readlink = gfs2_readlink,
> .follow_link = gfs2_follow_link,
> - .permission = gfs2_permission,
> + .permission = gfs2_iop_permission,
> .setattr = gfs2_setattr,
> .getattr = gfs2_getattr,
> .setxattr = gfs2_setxattr,
--
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