[libvirt] [PATCH 5/4] security: Don't try to lock NULL paths

[John Ferlan]

On 9/25/18 3:34 AM, Michal Privoznik wrote:
> It may happen that in the list of paths/disk sources to relabel
> there is a disk source. If that is the case, the path is NULL. In
> that case, we shouldn't try to lock the path. It's likely a
> network disk anyway and therefore there is nothing to lock.

I think this needs a tweak to reference commit 6d855abc1 which only
filtered if the provided @p was a directory. This adds another filter
when @p is NULL such as would be the case with networked storage.

NB: The storage source is only passed for DAC and not selinux. The DAC
code makes a some valiant attempts at src->path if not Local too. The
selinux code has lots of branches and callers which seem to validly pass
a path, but I could have missed a path or some nuance.

The "key" is chasing virSecurityDACChownListAppend and
virSecuritySELinuxContextListAppend where the list->[n]items is
populated via VIR_APPEND_ELEMENT. Expect to spend some time on the chase!

You already have an R-by and I don't have anything else to provide on
this particular one other than yeah, better safe than sorry and passing
NULL.  Although I have to imagine the stat(NULL, &s) in virFileIsDir
wouldn't have been pleased.

John

> 
> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> ---
>  src/security/security_dac.c     | 3 ++-
>  src/security/security_selinux.c | 3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/src/security/security_dac.c b/src/security/security_dac.c
> index 876cca0f2f..04168feb3d 100644
> --- a/src/security/security_dac.c
> +++ b/src/security/security_dac.c
> @@ -216,7 +216,8 @@ virSecurityDACTransactionRun(pid_t pid ATTRIBUTE_UNUSED,
>      for (i = 0; i < list->nItems; i++) {
>          const char *p = list->items[i]->path;
>  
> -        if (virFileIsDir(p))
> +        if (!p ||
> +            virFileIsDir(p))
>              continue;
>  
>          VIR_APPEND_ELEMENT_COPY_INPLACE(paths, npaths, p);
> diff --git a/src/security/security_selinux.c b/src/security/security_selinux.c
> index 3c847d8dcb..3adbeada14 100644
> --- a/src/security/security_selinux.c
> +++ b/src/security/security_selinux.c
> @@ -227,7 +227,8 @@ virSecuritySELinuxTransactionRun(pid_t pid ATTRIBUTE_UNUSED,
>      for (i = 0; i < list->nItems; i++) {
>          const char *p = list->items[i]->path;
>  
> -        if (virFileIsDir(p))
> +        if (!p ||
> +            virFileIsDir(p))
>              continue;
>  
>          VIR_APPEND_ELEMENT_COPY_INPLACE(paths, npaths, p);
>