Re: [lxc-devel] [PATCH] Parse rootfs->path

[Serge Hallyn]

Quoting Christian Brauner (christianvanbrau...@gmail.com):
> The mount_entry_overlay_dirs() and mount_entry_aufs_dirs() functions create
> workdirs and upperdirs for overlay and aufs lxc.mount.entry entries. They try
> to make sure that the workdirs and upperdirs can only be created under the
> containerdir (e.g. /path/to/the/container/CONTAINERNAME). In order to do this
> the right hand side of
> 
> if ((strncmp(upperdir, lxcpath, dirlen) == 0) && 
> (strncmp(upperdir, rootfs->path, rootfslen) != 0))
> 
> was thought to check if the rootfs->path is not present in the workdir and
> upperdir mount options. But the current check is bogus since it will be
> trivially true whenever the container is a block-dev or overlay or aufs backed
> since the rootfs->path will then have a form like e.g.
> 
> overlayfs:/some/path:/some/other/path
> 
> This patch parses rootfs->path by searching backwards for the first occurrence
> of the delimiter pair ":/". We do not simply search for ":" since it might be
> used in path names.
> 
> Signed-off-by: Christian Brauner 
> ---
>  src/lxc/conf.c | 126 
> ++---
>  1 file changed, 103 insertions(+), 23 deletions(-)
> 
> diff --git a/src/lxc/conf.c b/src/lxc/conf.c
> index 16a62f8..a730a67 100644
> --- a/src/lxc/conf.c
> +++ b/src/lxc/conf.c
> @@ -1821,6 +1821,11 @@ static int mount_entry_create_overlay_dirs(const 
> struct mntent *mntent,
>  const char *lxc_path)
>  {
>   char lxcpath[MAXPATHLEN];
> + char *end = NULL;
> + char *rootfsdir = NULL;
> + char *s = NULL;
> + char *s1 = NULL;
> + char *tmp = NULL;
>   char *upperdir = NULL;
>   char *workdir = NULL;
>   char **opts = NULL;
> @@ -1830,15 +1835,16 @@ static int mount_entry_create_overlay_dirs(const 
> struct mntent *mntent,
>   size_t i;
>   size_t len = 0;
>   size_t rootfslen = 0;
> + size_t slen = 0;
>  
>   if (!rootfs->path || !lxc_name || !lxc_path)
> - return -1;
> + goto err;
>  
>   opts = lxc_string_split(mntent->mnt_opts, ',');
>   if (opts)
>   arrlen = lxc_array_len((void **)opts);
>   else
> - return -1;
> + goto err;
>  
>   for (i = 0; i < arrlen; i++) {
>   if (strstr(opts[i], "upperdir=") && (strlen(opts[i]) > (len = 
> strlen("upperdir="
> @@ -1848,31 +1854,66 @@ static int mount_entry_create_overlay_dirs(const 
> struct mntent *mntent,
>   }
>  
>   ret = snprintf(lxcpath, MAXPATHLEN, "%s/%s", lxc_path, lxc_name);
> - if (ret < 0 || ret >= MAXPATHLEN) {
> - lxc_free_array((void **)opts, free);
> - return -1;
> - }
> + if (ret < 0 || ret >= MAXPATHLEN)
> + goto err;
>  
>   dirlen = strlen(lxcpath);
> - rootfslen = strlen(rootfs->path);
> +

Could you put this stuff into a helper, i.e.

rootfsdir = ovl_get_rootfs_dir(rootfs->path, );
> + s = strdup(rootfs->path);
> + if (!s)
> + goto err;
> +
> + s1 = malloc(strlen(rootfs->path) + 1);
> + if (!s1)
> + goto err;
> + end = stpcpy(s1, rootfs->path);
> +
> + /* If we find :/ in rootfs->path it means we either have a block-dev or
> +  * overlay or aufs container. */
> + while ((tmp = strrchr(s, ':'))) {
> + len = strlen(tmp);
> + rootfslen += len;
> + if (strncmp(tmp, ":/", 2) == 0) {
> + rootfsdir = end - rootfslen + 1;
> + rootfslen = strlen(rootfsdir);
> + break;
> + } else {
> + slen = strlen(s);
> + s[slen - len] = '\0';
> + }
> + }
> +
> + /* If rootfsdir is empty at this point we have a simple directory
> +  * container. */
> + if (!rootfsdir) {
> + rootfsdir = rootfs->path;
> + rootfslen = strlen(rootfs->path);
> + }
>  
>   /* We neither allow users to create upperdirs and workdirs outside the
>* containerdir nor inside the rootfs. The latter might be debatable. */
>   if (upperdir)
> - if ((strncmp(upperdir, lxcpath, dirlen) == 0) && 
> (strncmp(upperdir, rootfs->path, rootfslen) != 0))
> + if ((strncmp(upperdir, lxcpath, dirlen) == 0) && 
> (strncmp(upperdir, rootfsdir, rootfslen) != 0))
>   if (mkdir_p(upperdir, 0755) < 0) {
>   WARN("Failed to create upperdir");
>   }
>  
>  
>   if (workdir)
> - if ((strncmp(workdir, lxcpath, dirlen) == 0) && 
> (strncmp(workdir, rootfs->path, rootfslen) != 0))
> + if ((strncmp(workdir, lxcpath, dirlen) == 0) && 
> (strncmp(workdir, rootfsdir, rootfslen) != 0))
>   if (mkdir_p(workdir, 0755) < 0) {
>   

Re: [lxc-devel] [PATCH] Parse rootfs->path

[Christian Brauner]

On Mon, Oct 19, 2015 at 02:50:11PM +, Serge Hallyn wrote:
> Quoting Christian Brauner (christianvanbrau...@gmail.com):
> > The mount_entry_overlay_dirs() and mount_entry_aufs_dirs() functions create
> > workdirs and upperdirs for overlay and aufs lxc.mount.entry entries. They 
> > try
> > to make sure that the workdirs and upperdirs can only be created under the
> > containerdir (e.g. /path/to/the/container/CONTAINERNAME). In order to do 
> > this
> > the right hand side of
> > 
> > if ((strncmp(upperdir, lxcpath, dirlen) == 0) && 
> > (strncmp(upperdir, rootfs->path, rootfslen) != 0))
> > 
> > was thought to check if the rootfs->path is not present in the workdir and
> > upperdir mount options. But the current check is bogus since it will be
> > trivially true whenever the container is a block-dev or overlay or aufs 
> > backed
> > since the rootfs->path will then have a form like e.g.
> > 
> > overlayfs:/some/path:/some/other/path
> > 
> > This patch parses rootfs->path by searching backwards for the first 
> > occurrence
> > of the delimiter pair ":/". We do not simply search for ":" since it might 
> > be
> > used in path names.
> > 
> > Signed-off-by: Christian Brauner 
> > ---
> >  src/lxc/conf.c | 126 
> > ++---
> >  1 file changed, 103 insertions(+), 23 deletions(-)
> > 
> > diff --git a/src/lxc/conf.c b/src/lxc/conf.c
> > index 16a62f8..a730a67 100644
> > --- a/src/lxc/conf.c
> > +++ b/src/lxc/conf.c
> > @@ -1821,6 +1821,11 @@ static int mount_entry_create_overlay_dirs(const 
> > struct mntent *mntent,
> >const char *lxc_path)
> >  {
> > char lxcpath[MAXPATHLEN];
> > +   char *end = NULL;
> > +   char *rootfsdir = NULL;
> > +   char *s = NULL;
> > +   char *s1 = NULL;
> > +   char *tmp = NULL;
> > char *upperdir = NULL;
> > char *workdir = NULL;
> > char **opts = NULL;
> > @@ -1830,15 +1835,16 @@ static int mount_entry_create_overlay_dirs(const 
> > struct mntent *mntent,
> > size_t i;
> > size_t len = 0;
> > size_t rootfslen = 0;
> > +   size_t slen = 0;
> >  
> > if (!rootfs->path || !lxc_name || !lxc_path)
> > -   return -1;
> > +   goto err;
> >  
> > opts = lxc_string_split(mntent->mnt_opts, ',');
> > if (opts)
> > arrlen = lxc_array_len((void **)opts);
> > else
> > -   return -1;
> > +   goto err;
> >  
> > for (i = 0; i < arrlen; i++) {
> > if (strstr(opts[i], "upperdir=") && (strlen(opts[i]) > (len = 
> > strlen("upperdir="
> > @@ -1848,31 +1854,66 @@ static int mount_entry_create_overlay_dirs(const 
> > struct mntent *mntent,
> > }
> >  
> > ret = snprintf(lxcpath, MAXPATHLEN, "%s/%s", lxc_path, lxc_name);
> > -   if (ret < 0 || ret >= MAXPATHLEN) {
> > -   lxc_free_array((void **)opts, free);
> > -   return -1;
> > -   }
> > +   if (ret < 0 || ret >= MAXPATHLEN)
> > +   goto err;
> >  
> > dirlen = strlen(lxcpath);
> > -   rootfslen = strlen(rootfs->path);
> > +
> 
> Could you put this stuff into a helper, i.e.
Can do. Do you mean putting it as a static helper function in conf.c, or in
utils.c?

> 
>   rootfsdir = ovl_get_rootfs_dir(rootfs->path, );
> > +   s = strdup(rootfs->path);
> > +   if (!s)
> > +   goto err;
> > +
> > +   s1 = malloc(strlen(rootfs->path) + 1);
> > +   if (!s1)
> > +   goto err;
> > +   end = stpcpy(s1, rootfs->path);
> > +
> > +   /* If we find :/ in rootfs->path it means we either have a block-dev or
> > +* overlay or aufs container. */
> > +   while ((tmp = strrchr(s, ':'))) {
> > +   len = strlen(tmp);
> > +   rootfslen += len;
> > +   if (strncmp(tmp, ":/", 2) == 0) {
> > +   rootfsdir = end - rootfslen + 1;
> > +   rootfslen = strlen(rootfsdir);
> > +   break;
> > +   } else {
> > +   slen = strlen(s);
> > +   s[slen - len] = '\0';
> > +   }
> > +   }
> > +
> > +   /* If rootfsdir is empty at this point we have a simple directory
> > +* container. */
> > +   if (!rootfsdir) {
> > +   rootfsdir = rootfs->path;
> > +   rootfslen = strlen(rootfs->path);
> > +   }
> >  
> > /* We neither allow users to create upperdirs and workdirs outside the
> >  * containerdir nor inside the rootfs. The latter might be debatable. */
> > if (upperdir)
> > -   if ((strncmp(upperdir, lxcpath, dirlen) == 0) && 
> > (strncmp(upperdir, rootfs->path, rootfslen) != 0))
> > +   if ((strncmp(upperdir, lxcpath, dirlen) == 0) && 
> > (strncmp(upperdir, rootfsdir, rootfslen) != 0))
> > if (mkdir_p(upperdir, 0755) < 0) {
> > WARN("Failed to create upperdir");
> > }
> >  
> >  
> > if (workdir)
> > -   if ((strncmp(workdir, lxcpath, 

Re: [lxc-devel] [PATCH] Parse rootfs->path

[Serge Hallyn]

Quoting Christian Brauner (christianvanbrau...@gmail.com):
> On Mon, Oct 19, 2015 at 02:50:11PM +, Serge Hallyn wrote:
> > Quoting Christian Brauner (christianvanbrau...@gmail.com):
> > > The mount_entry_overlay_dirs() and mount_entry_aufs_dirs() functions 
> > > create
> > > workdirs and upperdirs for overlay and aufs lxc.mount.entry entries. They 
> > > try
> > > to make sure that the workdirs and upperdirs can only be created under the
> > > containerdir (e.g. /path/to/the/container/CONTAINERNAME). In order to do 
> > > this
> > > the right hand side of
> > > 
> > > if ((strncmp(upperdir, lxcpath, dirlen) == 0) && 
> > > (strncmp(upperdir, rootfs->path, rootfslen) != 0))
> > > 
> > > was thought to check if the rootfs->path is not present in the workdir and
> > > upperdir mount options. But the current check is bogus since it will be
> > > trivially true whenever the container is a block-dev or overlay or aufs 
> > > backed
> > > since the rootfs->path will then have a form like e.g.
> > > 
> > > overlayfs:/some/path:/some/other/path
> > > 
> > > This patch parses rootfs->path by searching backwards for the first 
> > > occurrence
> > > of the delimiter pair ":/". We do not simply search for ":" since it 
> > > might be
> > > used in path names.
> > > 
> > > Signed-off-by: Christian Brauner 
> > > ---
> > >  src/lxc/conf.c | 126 
> > > ++---
> > >  1 file changed, 103 insertions(+), 23 deletions(-)
> > > 
> > > diff --git a/src/lxc/conf.c b/src/lxc/conf.c
> > > index 16a62f8..a730a67 100644
> > > --- a/src/lxc/conf.c
> > > +++ b/src/lxc/conf.c
> > > @@ -1821,6 +1821,11 @@ static int mount_entry_create_overlay_dirs(const 
> > > struct mntent *mntent,
> > >  const char *lxc_path)
> > >  {
> > >   char lxcpath[MAXPATHLEN];
> > > + char *end = NULL;
> > > + char *rootfsdir = NULL;
> > > + char *s = NULL;
> > > + char *s1 = NULL;
> > > + char *tmp = NULL;
> > >   char *upperdir = NULL;
> > >   char *workdir = NULL;
> > >   char **opts = NULL;
> > > @@ -1830,15 +1835,16 @@ static int mount_entry_create_overlay_dirs(const 
> > > struct mntent *mntent,
> > >   size_t i;
> > >   size_t len = 0;
> > >   size_t rootfslen = 0;
> > > + size_t slen = 0;
> > >  
> > >   if (!rootfs->path || !lxc_name || !lxc_path)
> > > - return -1;
> > > + goto err;
> > >  
> > >   opts = lxc_string_split(mntent->mnt_opts, ',');
> > >   if (opts)
> > >   arrlen = lxc_array_len((void **)opts);
> > >   else
> > > - return -1;
> > > + goto err;
> > >  
> > >   for (i = 0; i < arrlen; i++) {
> > >   if (strstr(opts[i], "upperdir=") && (strlen(opts[i]) > (len = 
> > > strlen("upperdir="
> > > @@ -1848,31 +1854,66 @@ static int mount_entry_create_overlay_dirs(const 
> > > struct mntent *mntent,
> > >   }
> > >  
> > >   ret = snprintf(lxcpath, MAXPATHLEN, "%s/%s", lxc_path, lxc_name);
> > > - if (ret < 0 || ret >= MAXPATHLEN) {
> > > - lxc_free_array((void **)opts, free);
> > > - return -1;
> > > - }
> > > + if (ret < 0 || ret >= MAXPATHLEN)
> > > + goto err;
> > >  
> > >   dirlen = strlen(lxcpath);
> > > - rootfslen = strlen(rootfs->path);
> > > +
> > 
> > Could you put this stuff into a helper, i.e.
> Can do. Do you mean putting it as a static helper function in conf.c, or in
> utils.c?

That I'm not sure about.  It actually seems like the
mount_entry_create_{overlay,aufs}_dirs functions themselves could
stand to go elsewhere.  But that's probably best done after we
split src/lxc/bdev.c into src/lxc/bdev/file-per-backingstore

So for now probably just right here.  It keeps each fn simpler
and easier to read.
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