Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs fixes from Miklos Szeredi:

 - fix incomplete syncing of filesystem

 - fix regression in readdir on ovl over 9p

 - only follow redirects when needed

 - misc fixes and cleanups

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: fix overlay: warning prefix
  ovl: Use PTR_ERR_OR_ZERO()
  ovl: Sync upper dirty data when syncing overlayfs
  ovl: update ctx->pos on impure dir iteration
  ovl: Pass ovl_get_nlink() parameters in right order
  ovl: don't follow redirects if redirect_dir=off
This commit is contained in:
Linus Torvalds 2017-12-15 12:46:48 -08:00
commit 227701e0e7
8 changed files with 137 additions and 26 deletions

View File

@ -156,6 +156,40 @@ handle it in two different ways:
root of the overlay. Finally the directory is moved to the new
location.
There are several ways to tune the "redirect_dir" feature.
Kernel config options:
- OVERLAY_FS_REDIRECT_DIR:
If this is enabled, then redirect_dir is turned on by default.
- OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW:
If this is enabled, then redirects are always followed by default. Enabling
this results in a less secure configuration. Enable this option only when
worried about backward compatibility with kernels that have the redirect_dir
feature and follow redirects even if turned off.
Module options (can also be changed through /sys/module/overlay/parameters/*):
- "redirect_dir=BOOL":
See OVERLAY_FS_REDIRECT_DIR kernel config option above.
- "redirect_always_follow=BOOL":
See OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW kernel config option above.
- "redirect_max=NUM":
The maximum number of bytes in an absolute redirect (default is 256).
Mount options:
- "redirect_dir=on":
Redirects are enabled.
- "redirect_dir=follow":
Redirects are not created, but followed.
- "redirect_dir=off":
Redirects are not created and only followed if "redirect_always_follow"
feature is enabled in the kernel/module config.
- "redirect_dir=nofollow":
Redirects are not created and not followed (equivalent to "redirect_dir=off"
if "redirect_always_follow" feature is not enabled).
Non-directories
---------------

View File

@ -24,6 +24,16 @@ config OVERLAY_FS_REDIRECT_DIR
an overlay which has redirects on a kernel that doesn't support this
feature will have unexpected results.
config OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW
bool "Overlayfs: follow redirects even if redirects are turned off"
default y
depends on OVERLAY_FS
help
Disable this to get a possibly more secure configuration, but that
might not be backward compatible with previous kernels.
For more information, see Documentation/filesystems/overlayfs.txt
config OVERLAY_FS_INDEX
bool "Overlayfs: turn on inodes index feature by default"
depends on OVERLAY_FS

View File

@ -887,7 +887,8 @@ static int ovl_set_redirect(struct dentry *dentry, bool samedir)
spin_unlock(&dentry->d_lock);
} else {
kfree(redirect);
pr_warn_ratelimited("overlay: failed to set redirect (%i)\n", err);
pr_warn_ratelimited("overlayfs: failed to set redirect (%i)\n",
err);
/* Fall back to userspace copy-up */
err = -EXDEV;
}

View File

@ -435,7 +435,7 @@ int ovl_verify_index(struct dentry *index, struct ovl_path *lower,
/* Check if index is orphan and don't warn before cleaning it */
if (d_inode(index)->i_nlink == 1 &&
ovl_get_nlink(index, origin.dentry, 0) == 0)
ovl_get_nlink(origin.dentry, index, 0) == 0)
err = -ENOENT;
dput(origin.dentry);
@ -681,6 +681,22 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
if (d.stop)
break;
/*
* Following redirects can have security consequences: it's like
* a symlink into the lower layer without the permission checks.
* This is only a problem if the upper layer is untrusted (e.g
* comes from an USB drive). This can allow a non-readable file
* or directory to become readable.
*
* Only following redirects when redirects are enabled disables
* this attack vector when not necessary.
*/
err = -EPERM;
if (d.redirect && !ofs->config.redirect_follow) {
pr_warn_ratelimited("overlay: refusing to follow redirect for (%pd2)\n", dentry);
goto out_put;
}
if (d.redirect && d.redirect[0] == '/' && poe != roe) {
poe = roe;

View File

@ -180,7 +180,7 @@ static inline int ovl_do_whiteout(struct inode *dir, struct dentry *dentry)
static inline struct dentry *ovl_do_tmpfile(struct dentry *dentry, umode_t mode)
{
struct dentry *ret = vfs_tmpfile(dentry, mode, 0);
int err = IS_ERR(ret) ? PTR_ERR(ret) : 0;
int err = PTR_ERR_OR_ZERO(ret);
pr_debug("tmpfile(%pd2, 0%o) = %i\n", dentry, mode, err);
return ret;

View File

@ -14,6 +14,8 @@ struct ovl_config {
char *workdir;
bool default_permissions;
bool redirect_dir;
bool redirect_follow;
const char *redirect_mode;
bool index;
};

View File

@ -499,7 +499,7 @@ out:
return err;
fail:
pr_warn_ratelimited("overlay: failed to look up (%s) for ino (%i)\n",
pr_warn_ratelimited("overlayfs: failed to look up (%s) for ino (%i)\n",
p->name, err);
goto out;
}
@ -663,7 +663,10 @@ static int ovl_iterate_real(struct file *file, struct dir_context *ctx)
return PTR_ERR(rdt.cache);
}
return iterate_dir(od->realfile, &rdt.ctx);
err = iterate_dir(od->realfile, &rdt.ctx);
ctx->pos = rdt.ctx.pos;
return err;
}

View File

@ -33,6 +33,13 @@ module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644);
MODULE_PARM_DESC(ovl_redirect_dir_def,
"Default to on or off for the redirect_dir feature");
static bool ovl_redirect_always_follow =
IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW);
module_param_named(redirect_always_follow, ovl_redirect_always_follow,
bool, 0644);
MODULE_PARM_DESC(ovl_redirect_always_follow,
"Follow redirects even if redirect_dir feature is turned off");
static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
module_param_named(index, ovl_index_def, bool, 0644);
MODULE_PARM_DESC(ovl_index_def,
@ -232,6 +239,7 @@ static void ovl_free_fs(struct ovl_fs *ofs)
kfree(ofs->config.lowerdir);
kfree(ofs->config.upperdir);
kfree(ofs->config.workdir);
kfree(ofs->config.redirect_mode);
if (ofs->creator_cred)
put_cred(ofs->creator_cred);
kfree(ofs);
@ -244,6 +252,7 @@ static void ovl_put_super(struct super_block *sb)
ovl_free_fs(ofs);
}
/* Sync real dirty inodes in upper filesystem (if it exists) */
static int ovl_sync_fs(struct super_block *sb, int wait)
{
struct ovl_fs *ofs = sb->s_fs_info;
@ -252,14 +261,24 @@ static int ovl_sync_fs(struct super_block *sb, int wait)
if (!ofs->upper_mnt)
return 0;
upper_sb = ofs->upper_mnt->mnt_sb;
if (!upper_sb->s_op->sync_fs)
/*
* If this is a sync(2) call or an emergency sync, all the super blocks
* will be iterated, including upper_sb, so no need to do anything.
*
* If this is a syncfs(2) call, then we do need to call
* sync_filesystem() on upper_sb, but enough if we do it when being
* called with wait == 1.
*/
if (!wait)
return 0;
/* real inodes have already been synced by sync_filesystem(ovl_sb) */
upper_sb = ofs->upper_mnt->mnt_sb;
down_read(&upper_sb->s_umount);
ret = upper_sb->s_op->sync_fs(upper_sb, wait);
ret = sync_filesystem(upper_sb);
up_read(&upper_sb->s_umount);
return ret;
}
@ -295,6 +314,11 @@ static bool ovl_force_readonly(struct ovl_fs *ofs)
return (!ofs->upper_mnt || !ofs->workdir);
}
static const char *ovl_redirect_mode_def(void)
{
return ovl_redirect_dir_def ? "on" : "off";
}
/**
* ovl_show_options
*
@ -313,12 +337,10 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
}
if (ofs->config.default_permissions)
seq_puts(m, ",default_permissions");
if (ofs->config.redirect_dir != ovl_redirect_dir_def)
seq_printf(m, ",redirect_dir=%s",
ofs->config.redirect_dir ? "on" : "off");
if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
if (ofs->config.index != ovl_index_def)
seq_printf(m, ",index=%s",
ofs->config.index ? "on" : "off");
seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
return 0;
}
@ -348,8 +370,7 @@ enum {
OPT_UPPERDIR,
OPT_WORKDIR,
OPT_DEFAULT_PERMISSIONS,
OPT_REDIRECT_DIR_ON,
OPT_REDIRECT_DIR_OFF,
OPT_REDIRECT_DIR,
OPT_INDEX_ON,
OPT_INDEX_OFF,
OPT_ERR,
@ -360,8 +381,7 @@ static const match_table_t ovl_tokens = {
{OPT_UPPERDIR, "upperdir=%s"},
{OPT_WORKDIR, "workdir=%s"},
{OPT_DEFAULT_PERMISSIONS, "default_permissions"},
{OPT_REDIRECT_DIR_ON, "redirect_dir=on"},
{OPT_REDIRECT_DIR_OFF, "redirect_dir=off"},
{OPT_REDIRECT_DIR, "redirect_dir=%s"},
{OPT_INDEX_ON, "index=on"},
{OPT_INDEX_OFF, "index=off"},
{OPT_ERR, NULL}
@ -390,10 +410,37 @@ static char *ovl_next_opt(char **s)
return sbegin;
}
static int ovl_parse_redirect_mode(struct ovl_config *config, const char *mode)
{
if (strcmp(mode, "on") == 0) {
config->redirect_dir = true;
/*
* Does not make sense to have redirect creation without
* redirect following.
*/
config->redirect_follow = true;
} else if (strcmp(mode, "follow") == 0) {
config->redirect_follow = true;
} else if (strcmp(mode, "off") == 0) {
if (ovl_redirect_always_follow)
config->redirect_follow = true;
} else if (strcmp(mode, "nofollow") != 0) {
pr_err("overlayfs: bad mount option \"redirect_dir=%s\"\n",
mode);
return -EINVAL;
}
return 0;
}
static int ovl_parse_opt(char *opt, struct ovl_config *config)
{
char *p;
config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
if (!config->redirect_mode)
return -ENOMEM;
while ((p = ovl_next_opt(&opt)) != NULL) {
int token;
substring_t args[MAX_OPT_ARGS];
@ -428,12 +475,11 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
config->default_permissions = true;
break;
case OPT_REDIRECT_DIR_ON:
config->redirect_dir = true;
break;
case OPT_REDIRECT_DIR_OFF:
config->redirect_dir = false;
case OPT_REDIRECT_DIR:
kfree(config->redirect_mode);
config->redirect_mode = match_strdup(&args[0]);
if (!config->redirect_mode)
return -ENOMEM;
break;
case OPT_INDEX_ON:
@ -458,7 +504,7 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
config->workdir = NULL;
}
return 0;
return ovl_parse_redirect_mode(config, config->redirect_mode);
}
#define OVL_WORKDIR_NAME "work"
@ -1160,7 +1206,6 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
if (!cred)
goto out_err;
ofs->config.redirect_dir = ovl_redirect_dir_def;
ofs->config.index = ovl_index_def;
err = ovl_parse_opt((char *) data, &ofs->config);
if (err)