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Subject[patch v2] gfs2: don't call permission()
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Date
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@suse.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@suse.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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