[PATCH] r/o bind mounts: elevate write count for xattr_permission() callers

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

[AV: add missing parts - removexattr() and nfsd posix acls, plug for a leak
spotted by Miklos]

Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index c593db0..c309c88 100644 (file)
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -658,14 +658,19 @@ nfsd4_setattr(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
                        return status;
                }
        }
+       status = mnt_want_write(cstate->current_fh.fh_export->ex_path.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_path.mnt);
        return status;
 }
 

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 18a4cc9..626dfd3 100644 (file)
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -2086,6 +2086,9 @@ nfsd_set_posix_acl(struct svc_fh *fhp, int type, struct posix_acl *acl)
        } else
                size = 0;
 
+       error = mnt_want_write(fhp->fh_export->ex_path.mnt);
+       if (error)
+               goto getout;
        if (size)
                error = vfs_setxattr(fhp->fh_dentry, name, value, size, 0);
        else {
@@ -2097,6 +2100,7 @@ nfsd_set_posix_acl(struct svc_fh *fhp, int type, struct posix_acl *acl)
                                error = 0;
                }
        }
+       mnt_drop_write(fhp->fh_export->ex_path.mnt);
 
 getout:
        kfree(value);

diff --git a/fs/xattr.c b/fs/xattr.c
index 3acab16..f7062da 100644 (file)
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -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, const char *name, int mask)
         * 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;
        }
@@ -262,7 +261,11 @@ sys_setxattr(char __user *path, char __user *name, void __user *value,
        error = user_path_walk(path, &nd);
        if (error)
                return error;
-       error = setxattr(nd.path.dentry, name, value, size, flags);
+       error = mnt_want_write(nd.path.mnt);
+       if (!error) {
+               error = setxattr(nd.path.dentry, name, value, size, flags);
+               mnt_drop_write(nd.path.mnt);
+       }
        path_put(&nd.path);
        return error;
 }
@@ -277,7 +280,11 @@ sys_lsetxattr(char __user *path, char __user *name, void __user *value,
        error = user_path_walk_link(path, &nd);
        if (error)
                return error;
-       error = setxattr(nd.path.dentry, name, value, size, flags);
+       error = mnt_want_write(nd.path.mnt);
+       if (!error) {
+               error = setxattr(nd.path.dentry, name, value, size, flags);
+               mnt_drop_write(nd.path.mnt);
+       }
        path_put(&nd.path);
        return error;
 }
@@ -295,7 +302,12 @@ sys_fsetxattr(int fd, char __user *name, void __user *value,
                return error;
        dentry = f->f_path.dentry;
        audit_inode(NULL, dentry);
-       error = setxattr(dentry, name, value, size, flags);
+       error = mnt_want_write(f->f_path.mnt);
+       if (!error) {
+               error = setxattr(dentry, name, value, size, flags);
+               mnt_drop_write(f->f_path.mnt);
+       }
+out_fput:
        fput(f);
        return error;
 }
@@ -482,7 +494,11 @@ sys_removexattr(char __user *path, char __user *name)
        error = user_path_walk(path, &nd);
        if (error)
                return error;
-       error = removexattr(nd.path.dentry, name);
+       error = mnt_want_write(nd.path.mnt);
+       if (!error) {
+               error = removexattr(nd.path.dentry, name);
+               mnt_drop_write(nd.path.mnt);
+       }
        path_put(&nd.path);
        return error;
 }
@@ -496,7 +512,11 @@ sys_lremovexattr(char __user *path, char __user *name)
        error = user_path_walk_link(path, &nd);
        if (error)
                return error;
-       error = removexattr(nd.path.dentry, name);
+       error = mnt_want_write(nd.path.mnt);
+       if (!error) {
+               error = removexattr(nd.path.dentry, name);
+               mnt_drop_write(nd.path.mnt);
+       }
        path_put(&nd.path);
        return error;
 }
@@ -513,7 +533,11 @@ sys_fremovexattr(int fd, char __user *name)
                return error;
        dentry = f->f_path.dentry;
        audit_inode(NULL, dentry);
-       error = removexattr(dentry, name);
+       error = mnt_want_write(f->f_path.mnt);
+       if (!error) {
+               error = removexattr(dentry, name);
+               mnt_drop_write(f->f_path.mnt);
+       }
        fput(f);
        return error;
 }