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authorDavid Howells <dhowells@redhat.com>2018-11-04 07:43:08 -0500
committerAl Viro <viro@zeniv.linux.org.uk>2019-01-30 17:44:25 -0500
commit132e460848f4261b8a6b9c28fae52bf9e02b52fd (patch)
tree6efa9049652905a5931b564a64d0aa609979d91b /fs/namespace.c
parenta0c9a8b8fd9fd572b0d60276beb2142c8f59f9b8 (diff)
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new helper: do_new_mount_fc()
Create an fs_context-aware version of do_new_mount(). This takes an fs_context with a superblock already attached to it. Make do_new_mount() use do_new_mount_fc() rather than do_new_mount(); this allows the consolidation of the mount creation, check and add steps. To make this work, mount_too_revealing() is changed to take a superblock rather than a mount (which the fs_context doesn't have available), allowing this check to be done before the mount object is created. Signed-off-by: David Howells <dhowells@redhat.com> Co-developed-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/namespace.c')
-rw-r--r--fs/namespace.c65
1 files changed, 39 insertions, 26 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index 0354cb6ac2d3..f629e1c7f3cc 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2523,7 +2523,37 @@ unlock:
return err;
}
-static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags);
+static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags);
+
+/*
+ * Create a new mount using a superblock configuration and request it
+ * be added to the namespace tree.
+ */
+static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint,
+ unsigned int mnt_flags)
+{
+ struct vfsmount *mnt;
+ struct super_block *sb = fc->root->d_sb;
+ int error;
+
+ if (mount_too_revealing(sb, &mnt_flags)) {
+ dput(fc->root);
+ fc->root = NULL;
+ deactivate_locked_super(sb);
+ return -EPERM;
+ }
+
+ up_write(&sb->s_umount);
+
+ mnt = vfs_create_mount(fc);
+ if (IS_ERR(mnt))
+ return PTR_ERR(mnt);
+
+ error = do_add_mount(real_mount(mnt), mountpoint, mnt_flags);
+ if (error < 0)
+ mntput(mnt);
+ return error;
+}
/*
* create a new mount for userspace and request it to be added into the
@@ -2533,7 +2563,6 @@ static int do_new_mount(struct path *path, const char *fstype, int sb_flags,
int mnt_flags, const char *name, void *data)
{
struct file_system_type *type;
- struct vfsmount *mnt;
struct fs_context *fc;
const char *subtype = NULL;
int err = 0;
@@ -2577,26 +2606,9 @@ static int do_new_mount(struct path *path, const char *fstype, int sb_flags,
err = parse_monolithic_mount_data(fc, data);
if (!err)
err = vfs_get_tree(fc);
- if (err)
- goto out;
-
- up_write(&fc->root->d_sb->s_umount);
- mnt = vfs_create_mount(fc);
- if (IS_ERR(mnt)) {
- err = PTR_ERR(mnt);
- goto out;
- }
-
- if (mount_too_revealing(mnt, &mnt_flags)) {
- mntput(mnt);
- err = -EPERM;
- goto out;
- }
+ if (!err)
+ err = do_new_mount_fc(fc, path, mnt_flags);
- err = do_add_mount(real_mount(mnt), path, mnt_flags);
- if (err)
- mntput(mnt);
-out:
put_fs_context(fc);
return err;
}
@@ -3421,7 +3433,8 @@ bool current_chrooted(void)
return chrooted;
}
-static bool mnt_already_visible(struct mnt_namespace *ns, struct vfsmount *new,
+static bool mnt_already_visible(struct mnt_namespace *ns,
+ const struct super_block *sb,
int *new_mnt_flags)
{
int new_flags = *new_mnt_flags;
@@ -3433,7 +3446,7 @@ static bool mnt_already_visible(struct mnt_namespace *ns, struct vfsmount *new,
struct mount *child;
int mnt_flags;
- if (mnt->mnt.mnt_sb->s_type != new->mnt_sb->s_type)
+ if (mnt->mnt.mnt_sb->s_type != sb->s_type)
continue;
/* This mount is not fully visible if it's root directory
@@ -3484,7 +3497,7 @@ found:
return visible;
}
-static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags)
+static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags)
{
const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV;
struct mnt_namespace *ns = current->nsproxy->mnt_ns;
@@ -3494,7 +3507,7 @@ static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags)
return false;
/* Can this filesystem be too revealing? */
- s_iflags = mnt->mnt_sb->s_iflags;
+ s_iflags = sb->s_iflags;
if (!(s_iflags & SB_I_USERNS_VISIBLE))
return false;
@@ -3504,7 +3517,7 @@ static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags)
return true;
}
- return !mnt_already_visible(ns, mnt, new_mnt_flags);
+ return !mnt_already_visible(ns, sb, new_mnt_flags);
}
bool mnt_may_suid(struct vfsmount *mnt)