This patch hides error about missing lowerdir if MS_SILENT is set.
We use mount(NULL, "/", "overlay", MS_SILENT, NULL) for testing support of
overlayfs: syscall returns -ENODEV if it's not supported. Otherwise kernel
automatically loads module and returns -EINVAL because lowerdir is missing.
Signed-off-by: Konstantin Khlebnikov <[email protected]>
---
fs/overlayfs/super.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index bf8537c7f455..00e1d0b3abdd 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -840,7 +840,8 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
err = -EINVAL;
if (!ufs->config.lowerdir) {
- pr_err("overlayfs: missing 'lowerdir'\n");
+ if (!silent)
+ pr_err("overlayfs: missing 'lowerdir'\n");
goto out_free_config;
}
Overlayfs opens files directly at underlying filesystem. File->f_path.mnt
points to private clone of lower/upper mount. Thus MS_NOEXEC at overlayfs
mount has no effect because all checks are done against underlying mount.
This patch clears "noexec" at private lower/upper mounts (if noexec isn't
locked) and checks MNT_NOEXEC in overlayfs mount flags in ->dentry_open().
MS_NODEV already works correctly because kernel checks it before opening.
Signed-off-by: Konstantin Khlebnikov <[email protected]>
---
Documentation/filesystems/Locking | 2 +-
Documentation/filesystems/vfs.txt | 2 +-
fs/open.c | 2 +-
fs/overlayfs/inode.c | 14 ++++++++++++--
fs/overlayfs/super.c | 14 ++++++++++++++
include/linux/fs.h | 3 ++-
6 files changed, 31 insertions(+), 6 deletions(-)
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 6a34a0f4d37c..f949910a9ff8 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -67,7 +67,7 @@ prototypes:
struct file *, unsigned open_flag,
umode_t create_mode, int *opened);
int (*tmpfile) (struct inode *, struct dentry *, umode_t);
- int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
+ int (*dentry_open)(struct path *, struct file *, const struct cred *);
locking rules:
all may block
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 5eb8456fc41e..f5557f06ce12 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -364,7 +364,7 @@ struct inode_operations {
int (*atomic_open)(struct inode *, struct dentry *, struct file *,
unsigned open_flag, umode_t create_mode, int *opened);
int (*tmpfile) (struct inode *, struct dentry *, umode_t);
- int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
+ int (*dentry_open)(struct path *, struct file *, const struct cred *);
};
Again, all methods are called without any locks being held, unless
diff --git a/fs/open.c b/fs/open.c
index e0250bdcc440..b619e28b2740 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -865,7 +865,7 @@ int vfs_open(const struct path *path, struct file *filp,
struct inode *inode = path->dentry->d_inode;
if (inode->i_op->dentry_open)
- return inode->i_op->dentry_open(path->dentry, filp, cred);
+ return inode->i_op->dentry_open(path, filp, cred);
else {
filp->f_path = *path;
return do_dentry_open(filp, NULL, cred);
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 308379b2d0b2..b9a40c8dbd1e 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -10,6 +10,7 @@
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/xattr.h>
+#include <linux/mount.h>
#include "overlayfs.h"
static int ovl_copy_up_last(struct dentry *dentry, struct iattr *attr,
@@ -337,14 +338,23 @@ static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
return true;
}
-static int ovl_dentry_open(struct dentry *dentry, struct file *file,
- const struct cred *cred)
+static int ovl_dentry_open(const struct path *path, struct file *file,
+ const struct cred *cred)
{
+ struct dentry *dentry = path->dentry;
int err;
struct path realpath;
enum ovl_path_type type;
bool want_write = false;
+ /*
+ * After opening file->f_path.mnt points to private lower/upper mount.
+ * Here is the last chance to check flags at overlayfs mount.
+ */
+ if ((file->f_flags & __FMODE_EXEC) &&
+ (path->mnt->mnt_flags & MNT_NOEXEC))
+ return -EACCES;
+
type = ovl_path_real(dentry, &realpath);
if (ovl_open_need_copy_up(file->f_flags, type, realpath.dentry)) {
want_write = true;
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 00e1d0b3abdd..64c3714acf38 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -923,6 +923,13 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
goto out_put_lowerpath;
}
+ /*
+ * Drop noexec at upper mount if allowed. We'll check
+ * MNT_NOEXEC at overlayfs mount in ovl_dentry_open().
+ */
+ if (!(ufs->upper_mnt->mnt_flags & MNT_LOCK_NOEXEC))
+ ufs->upper_mnt->mnt_flags &= ~MNT_NOEXEC;
+
ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
err = PTR_ERR(ufs->workdir);
if (IS_ERR(ufs->workdir)) {
@@ -951,6 +958,13 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
*/
mnt->mnt_flags |= MNT_READONLY;
+ /*
+ * Drop noexec at lower mount if allowed. We'll check
+ * MNT_NOEXEC at overlayfs mount in ovl_dentry_open().
+ */
+ if (!(mnt->mnt_flags & MNT_LOCK_NOEXEC))
+ mnt->mnt_flags &= ~MNT_NOEXEC;
+
ufs->lower_mnt[ufs->numlower] = mnt;
ufs->numlower++;
}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e351da4a934f..55c3edd9519e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1653,7 +1653,8 @@ struct inode_operations {
int (*set_acl)(struct inode *, struct posix_acl *, int);
/* WARNING: probably going away soon, do not use! */
- int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
+ int (*dentry_open)(const struct path *, struct file *,
+ const struct cred *);
} ____cacheline_aligned;
ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
Mount flag MS_NOSUID in overlayfs has the same problem as MS_NOEXEC:
overlayfs opens files at underlying filesystem thus kernel check flags
at private clone of lower/upper mountpoint instead of overlayfs itself.
This patch saves MNT_NOSUID from overlayfs mount in file->f_mode when
opens file and checks it together with MNT_NOSUID. This behavior
stricter than usual: opened file stays nosuid even after remounting
overlayfs without MS_NOSUID but that should be fine.
Signed-off-by: Konstantin Khlebnikov <[email protected]>
---
fs/exec.c | 3 ++-
fs/overlayfs/inode.c | 4 ++++
fs/overlayfs/super.c | 6 ++++++
include/linux/fs.h | 3 +++
security/commoncap.c | 3 ++-
security/selinux/hooks.c | 3 ++-
6 files changed, 19 insertions(+), 3 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index 1977c2a553ac..0d81c6a43ef4 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1289,7 +1289,8 @@ static void bprm_fill_uid(struct linux_binprm *bprm)
bprm->cred->euid = current_euid();
bprm->cred->egid = current_egid();
- if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)
+ if ((bprm->file->f_mode & FMODE_NOSUID) ||
+ (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID))
return;
if (task_no_new_privs(current))
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index b9a40c8dbd1e..13be68335b1d 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -373,6 +373,10 @@ static int ovl_dentry_open(const struct path *path, struct file *file,
}
err = vfs_open(&realpath, file, cred);
+
+ if (path->mnt->mnt_flags & MNT_NOSUID)
+ file->f_mode |= FMODE_NOSUID;
+
out_drop_write:
if (want_write)
ovl_drop_write(dentry);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 64c3714acf38..e5db31f78c7d 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -930,6 +930,9 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
if (!(ufs->upper_mnt->mnt_flags & MNT_LOCK_NOEXEC))
ufs->upper_mnt->mnt_flags &= ~MNT_NOEXEC;
+ if (!(ufs->upper_mnt->mnt_flags & MNT_LOCK_NOSUID))
+ ufs->upper_mnt->mnt_flags &= ~MNT_NOSUID;
+
ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
err = PTR_ERR(ufs->workdir);
if (IS_ERR(ufs->workdir)) {
@@ -965,6 +968,9 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
if (!(mnt->mnt_flags & MNT_LOCK_NOEXEC))
mnt->mnt_flags &= ~MNT_NOEXEC;
+ if (!(mnt->mnt_flags & MNT_LOCK_NOSUID))
+ mnt->mnt_flags &= ~MNT_NOSUID;
+
ufs->lower_mnt[ufs->numlower] = mnt;
ufs->numlower++;
}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 55c3edd9519e..abc5cd658ad0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -136,6 +136,9 @@ typedef void (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
/* Has write method(s) */
#define FMODE_CAN_WRITE ((__force fmode_t)0x40000)
+/* Ignode S_ISUID and S_ISGID bits when executing this file */
+#define FMODE_NOSUID ((__force fmode_t)0x80000)
+
/* File was opened by fanotify and shouldn't generate fanotify events */
#define FMODE_NONOTIFY ((__force fmode_t)0x4000000)
diff --git a/security/commoncap.c b/security/commoncap.c
index d103f5a4043d..15deb600503b 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -437,7 +437,8 @@ static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_c
if (!file_caps_enabled)
return 0;
- if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)
+ if ((bprm->file->f_mode & FMODE_NOSUID) ||
+ (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID))
return 0;
rc = get_vfs_caps_from_disk(bprm->file->f_path.dentry, &vcaps);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 623108199641..437e0e131fbd 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2137,7 +2137,8 @@ static int check_nnp_nosuid(const struct linux_binprm *bprm,
const struct task_security_struct *new_tsec)
{
int nnp = (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS);
- int nosuid = (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID);
+ int nosuid = (bprm->file->f_mode & FMODE_NOSUID) ||
+ (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID);
int rc;
if (!nnp && !nosuid)
Mounting overlayfs using other overlayfs instance as lower or upper
layer triggers false-positive lockdep warning about possible locking
recursion of ->i_mutex in iterate_dir().
Nesting already limited with FILESYSTEM_MAX_STACK_DEPTH = 2 to prevent
kernel stack overflow. Overlayfs supports multiple lower layers thus
the same configuration could be constructed without nesting.
Signed-off-by: Konstantin Khlebnikov <[email protected]>
---
fs/overlayfs/super.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index e5db31f78c7d..381af9a5ece9 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -700,10 +700,13 @@ static bool ovl_is_allowed_fs_type(struct dentry *root)
/*
* We don't support:
+ * - overlayfs
* - automount filesystems
* - filesystems with revalidate (FIXME for lower layer)
* - filesystems with case insensitive names
*/
+ if (root->d_sb->s_op == &ovl_super_operations)
+ return false;
if (dop &&
(dop->d_manage || dop->d_automount ||
dop->d_revalidate || dop->d_weak_revalidate ||
On Mon, Jun 29, 2015 at 7:18 PM, Konstantin Khlebnikov
<[email protected]> wrote:
> This patch hides error about missing lowerdir if MS_SILENT is set.
>
> We use mount(NULL, "/", "overlay", MS_SILENT, NULL) for testing support of
> overlayfs: syscall returns -ENODEV if it's not supported. Otherwise kernel
> automatically loads module and returns -EINVAL because lowerdir is missing.
Queued.
Thanks,
Miklos