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-rw-r--r--fs/fuse/dir.c40
-rw-r--r--fs/fuse/fuse_i.h3
-rw-r--r--fs/fuse/inode.c12
3 files changed, 49 insertions, 6 deletions
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index f127625543b4..65da6e1b6de5 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -411,17 +411,45 @@ int fuse_do_getattr(struct inode *inode)
return err;
}
+/*
+ * Calling into a user-controlled filesystem gives the filesystem
+ * daemon ptrace-like capabilities over the requester process. This
+ * means, that the filesystem daemon is able to record the exact
+ * filesystem operations performed, and can also control the behavior
+ * of the requester process in otherwise impossible ways. For example
+ * it can delay the operation for arbitrary length of time allowing
+ * DoS against the requester.
+ *
+ * For this reason only those processes can call into the filesystem,
+ * for which the owner of the mount has ptrace privilege. This
+ * excludes processes started by other users, suid or sgid processes.
+ */
+static int fuse_allow_task(struct fuse_conn *fc, struct task_struct *task)
+{
+ if (fc->flags & FUSE_ALLOW_OTHER)
+ return 1;
+
+ if (task->euid == fc->user_id &&
+ task->suid == fc->user_id &&
+ task->uid == fc->user_id &&
+ task->egid == fc->group_id &&
+ task->sgid == fc->group_id &&
+ task->gid == fc->group_id)
+ return 1;
+
+ return 0;
+}
+
static int fuse_revalidate(struct dentry *entry)
{
struct inode *inode = entry->d_inode;
struct fuse_inode *fi = get_fuse_inode(inode);
struct fuse_conn *fc = get_fuse_conn(inode);
- if (get_node_id(inode) == FUSE_ROOT_ID) {
- if (!(fc->flags & FUSE_ALLOW_OTHER) &&
- current->fsuid != fc->user_id)
- return -EACCES;
- } else if (time_before_eq(jiffies, fi->i_time))
+ if (!fuse_allow_task(fc, current))
+ return -EACCES;
+ if (get_node_id(inode) != FUSE_ROOT_ID &&
+ time_before_eq(jiffies, fi->i_time))
return 0;
return fuse_do_getattr(inode);
@@ -431,7 +459,7 @@ static int fuse_permission(struct inode *inode, int mask, struct nameidata *nd)
{
struct fuse_conn *fc = get_fuse_conn(inode);
- if (!(fc->flags & FUSE_ALLOW_OTHER) && current->fsuid != fc->user_id)
+ if (!fuse_allow_task(fc, current))
return -EACCES;
else if (fc->flags & FUSE_DEFAULT_PERMISSIONS) {
int err = generic_permission(inode, mask, NULL);
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index aff3a01ea02b..3ec2aff3fdb5 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -198,6 +198,9 @@ struct fuse_conn {
/** The user id for this mount */
uid_t user_id;
+ /** The group id for this mount */
+ gid_t group_id;
+
/** The fuse mount flags for this mount */
unsigned flags;
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 0b75c73386e9..c8e54c0658f1 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -31,6 +31,7 @@ struct fuse_mount_data {
int fd;
unsigned rootmode;
unsigned user_id;
+ unsigned group_id;
unsigned flags;
unsigned max_read;
};
@@ -199,6 +200,7 @@ static void fuse_put_super(struct super_block *sb)
spin_lock(&fuse_lock);
fc->mounted = 0;
fc->user_id = 0;
+ fc->group_id = 0;
fc->flags = 0;
/* Flush all readers on this fs */
wake_up_all(&fc->waitq);
@@ -248,6 +250,7 @@ enum {
OPT_FD,
OPT_ROOTMODE,
OPT_USER_ID,
+ OPT_GROUP_ID,
OPT_DEFAULT_PERMISSIONS,
OPT_ALLOW_OTHER,
OPT_KERNEL_CACHE,
@@ -259,6 +262,7 @@ static match_table_t tokens = {
{OPT_FD, "fd=%u"},
{OPT_ROOTMODE, "rootmode=%o"},
{OPT_USER_ID, "user_id=%u"},
+ {OPT_GROUP_ID, "group_id=%u"},
{OPT_DEFAULT_PERMISSIONS, "default_permissions"},
{OPT_ALLOW_OTHER, "allow_other"},
{OPT_KERNEL_CACHE, "kernel_cache"},
@@ -300,6 +304,12 @@ static int parse_fuse_opt(char *opt, struct fuse_mount_data *d)
d->user_id = value;
break;
+ case OPT_GROUP_ID:
+ if (match_int(&args[0], &value))
+ return 0;
+ d->group_id = value;
+ break;
+
case OPT_DEFAULT_PERMISSIONS:
d->flags |= FUSE_DEFAULT_PERMISSIONS;
break;
@@ -333,6 +343,7 @@ static int fuse_show_options(struct seq_file *m, struct vfsmount *mnt)
struct fuse_conn *fc = get_fuse_conn_super(mnt->mnt_sb);
seq_printf(m, ",user_id=%u", fc->user_id);
+ seq_printf(m, ",group_id=%u", fc->group_id);
if (fc->flags & FUSE_DEFAULT_PERMISSIONS)
seq_puts(m, ",default_permissions");
if (fc->flags & FUSE_ALLOW_OTHER)
@@ -465,6 +476,7 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
fc->flags = d.flags;
fc->user_id = d.user_id;
+ fc->group_id = d.group_id;
fc->max_read = d.max_read;
if (fc->max_read / PAGE_CACHE_SIZE < fc->bdi.ra_pages)
fc->bdi.ra_pages = fc->max_read / PAGE_CACHE_SIZE;