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    Subject[PATCH 10/27] r-o-bind-mounts-elevate-mount-count-for-extended-attributes
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    Date

    This basically audits the callers of xattr_permission(), which calls
    permission() and can perform writes to the filesystem.

    Acked-by: Christoph Hellwig <hch@infradead.org>
    Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    ---

    linux-2.6.git-dave/fs/nfsd/nfs4proc.c | 7 ++++++-
    linux-2.6.git-dave/fs/xattr.c | 16 ++++++++++++++--
    2 files changed, 20 insertions(+), 3 deletions(-)

    diff -puN fs/nfsd/nfs4proc.c~r-o-bind-mounts-elevate-mount-count-for-extended-attributes fs/nfsd/nfs4proc.c
    --- linux-2.6.git/fs/nfsd/nfs4proc.c~r-o-bind-mounts-elevate-mount-count-for-extended-attributes 2007-11-01 14:46:11.000000000 -0700
    +++ linux-2.6.git-dave/fs/nfsd/nfs4proc.c 2007-11-01 14:46:11.000000000 -0700
    @@ -658,14 +658,19 @@ nfsd4_setattr(struct svc_rqst *rqstp, st
    return status;
    }
    }
    + status = mnt_want_write(cstate->current_fh.fh_export->ex_mnt);
    + if (status)
    + return status;
    status = nfs_ok;
    if (setattr->sa_acl != NULL)
    status = nfsd4_set_nfs4_acl(rqstp, &cstate->current_fh,
    setattr->sa_acl);
    if (status)
    - return status;
    + goto out;
    status = nfsd_setattr(rqstp, &cstate->current_fh, &setattr->sa_iattr,
    0, (time_t)0);
    +out:
    + mnt_drop_write(cstate->current_fh.fh_export->ex_mnt);
    return status;
    }

    diff -puN fs/xattr.c~r-o-bind-mounts-elevate-mount-count-for-extended-attributes fs/xattr.c
    --- linux-2.6.git/fs/xattr.c~r-o-bind-mounts-elevate-mount-count-for-extended-attributes 2007-11-01 14:46:11.000000000 -0700
    +++ linux-2.6.git-dave/fs/xattr.c 2007-11-01 14:46:11.000000000 -0700
    @@ -11,6 +11,7 @@
    #include <linux/slab.h>
    #include <linux/file.h>
    #include <linux/xattr.h>
    +#include <linux/mount.h>
    #include <linux/namei.h>
    #include <linux/security.h>
    #include <linux/syscalls.h>
    @@ -32,8 +33,6 @@ xattr_permission(struct inode *inode, co
    * filesystem or on an immutable / append-only inode.
    */
    if (mask & MAY_WRITE) {
    - if (IS_RDONLY(inode))
    - return -EROFS;
    if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
    return -EPERM;
    }
    @@ -235,7 +234,11 @@ sys_setxattr(char __user *path, char __u
    error = user_path_walk(path, &nd);
    if (error)
    return error;
    + error = mnt_want_write(nd.mnt);
    + if (error)
    + return error;
    error = setxattr(nd.dentry, name, value, size, flags);
    + mnt_drop_write(nd.mnt);
    path_release(&nd);
    return error;
    }
    @@ -250,7 +253,11 @@ sys_lsetxattr(char __user *path, char __
    error = user_path_walk_link(path, &nd);
    if (error)
    return error;
    + error = mnt_want_write(nd.mnt);
    + if (error)
    + return error;
    error = setxattr(nd.dentry, name, value, size, flags);
    + mnt_drop_write(nd.mnt);
    path_release(&nd);
    return error;
    }
    @@ -266,9 +273,14 @@ sys_fsetxattr(int fd, char __user *name,
    f = fget(fd);
    if (!f)
    return error;
    + error = mnt_want_write(f->f_vfsmnt);
    + if (error)
    + goto out_fput;
    dentry = f->f_path.dentry;
    audit_inode(NULL, dentry);
    error = setxattr(dentry, name, value, size, flags);
    + mnt_drop_write(f->f_vfsmnt);
    +out_fput:
    fput(f);
    return error;
    }
    _
    -
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