Re: [PATCH] trans/mtab: avoid firmlink loops

[Samuel Thibault]

Justus Winter, le Sun 05 Oct 2014 13:26:42 +0200, a écrit :
> * trans/mtab.c (struct mtab): Add a hash table to keep track of seen
> ports.
> (mtab_mark_as_seen): New function that records the identity port of a
> given node in the hash table and reports whether it has been there
> before.
> (mtab_populate): Use the new function to avoid running in circles.
> (main, open_hook): Initialize hash table.
> (close_hook): Free ports and destroy hash table.

Yes, it does avoid loops, please commit, thanks!

> ---
>  trans/mtab.c | 46 +++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 45 insertions(+), 1 deletion(-)
> 
> diff --git a/trans/mtab.c b/trans/mtab.c
> index 5207c1e..a9928b3 100644
> --- a/trans/mtab.c
> +++ b/trans/mtab.c
> @@ -24,6 +24,7 @@
>  #include <error.h>
>  #include <fcntl.h>
>  #include <hurd.h>
> +#include <hurd/ihash.h>
>  #include <hurd/trivfs.h>
>  #include <inttypes.h>
>  #include <mntent.h>
> @@ -55,6 +56,7 @@ struct mtab
>    char *contents;
>    size_t contents_len;
>    off_t offs;
> +  struct hurd_ihash ports_seen;
>  };
>  
>  const char *argp_program_version = STANDARD_HURD_VERSION (mtab);
> @@ -244,7 +246,11 @@ main (int argc, char *argv[])
>    else
>      {
>        /* One-shot mode.       */
> -      struct mtab mtab = { .lock = PTHREAD_MUTEX_INITIALIZER };
> +      struct mtab mtab =
> +        {
> +          .lock = PTHREAD_MUTEX_INITIALIZER,
> +          .ports_seen = HURD_IHASH_INITIALIZER (HURD_IHASH_NO_LOCP),
> +        };
>        err = mtab_populate (&mtab, target_path, insecure);
>        if (err)
>       error (5, err, "%s", target_path);
> @@ -301,6 +307,33 @@ is_filesystem_translator (file_t node)
>      }
>  }
>  
> +/* Records NODE's idport in ports_seen, returns true if we have
> +   already seen this node or there was an error getting the id
> +   port.  */
> +boolean_t
> +mtab_mark_as_seen (struct mtab *mtab, mach_port_t node)
> +{
> +  error_t err;
> +  mach_port_t idport, fsidport;
> +  ino_t fileno;
> +
> +  err = io_identity (node, &idport, &fsidport, &fileno);
> +  if (err)
> +    return TRUE;
> +
> +  mach_port_deallocate (mach_task_self (), fsidport);
> +
> +  if (hurd_ihash_find (&mtab->ports_seen, idport))
> +    {
> +      /* Already seen.  Get rid of the extra reference.  */
> +      mach_port_deallocate (mach_task_self (), idport);
> +      return TRUE;
> +    }
> +
> +  hurd_ihash_add (&mtab->ports_seen, idport, idport);
> +  return FALSE;
> +}
> +
>  /* Populates the given MTAB object with the information for PATH.  If
>     INSECURE is given, also follow translators bound to nodes not owned
>     by root or the current user.  */
> @@ -363,6 +396,13 @@ mtab_populate (struct mtab *mtab, const char *path, int 
> insecure)
>        goto errout;
>      }
>  
> +  /* Avoid running in circles.  */
> +  if (mtab_mark_as_seen (mtab, node))
> +    {
> +      err = 0;
> +      goto errout;
> +    }
> +
>    /* Query its options.       */
>    err = file_get_fs_options (node, &argz, &argz_len);
>    if (err)
> @@ -602,6 +642,7 @@ open_hook (struct trivfs_peropen *peropen)
>    mtab->offs = 0;
>    mtab->contents = NULL;
>    mtab->contents_len = 0;
> +  hurd_ihash_init (&mtab->ports_seen, HURD_IHASH_NO_LOCP);
>  
>    /* The mtab object is initialized, but not yet populated.  We delay
>       that until that data is really needed.  This avoids the following
> @@ -635,6 +676,9 @@ close_hook (struct trivfs_peropen *peropen)
>    struct mtab *op = peropen->hook;
>    pthread_mutex_destroy (&op->lock);
>    free (op->contents);
> +  HURD_IHASH_ITERATE (&op->ports_seen, p)
> +    mach_port_deallocate (mach_task_self (), (mach_port_t) p);
> +  hurd_ihash_destroy (&op->ports_seen);
>    free (op);
>  }
>  
> -- 
> 2.1.1
> 

-- 
Samuel
* D a decide de peter un cable dans son rapport de pfp
<c> et il a bien raison ;-)
<c> tu vas dire quoi ?
<D> j'ai mis les paroles de "le coq est mort" en en-tete
 -+- #ens-mim et la peufeupeu -+-