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Date: Fri, 26 Sep 2014 17:40:08 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2] qga: Rewrite code where using readdir_r
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To: zhanghailiang <zhang.zhanghailiang@huawei.com>, qemu-devel@nongnu.org
Cc: mdroth@linux.vnet.ibm.com, armbru@redhat.com, qemu-stable@nongnu.org, luonengjun@huawei.com, peter.huangpeng@huawei.com, lcapitulino@redhat.com

Il 19/09/2014 05:09, zhanghailiang ha scritto:
> If readdir_r fails, error_setg_errno will reference the freed
> pointer *dirpath*.
> 
> Moreover, readdir_r may cause a buffer overflow, using readdir instead.
> 
> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
> ---
>  v2:
> - Switch readdir_r to readdir (Comment of Eric Blake)
> ---
>  qga/commands-posix.c | 27 +++++++++++++++------------
>  1 file changed, 15 insertions(+), 12 deletions(-)
> 
> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> index 7eed7f4..f6f3e3c 100644
> --- a/qga/commands-posix.c
> +++ b/qga/commands-posix.c
> @@ -956,7 +956,7 @@ static void build_guest_fsinfo_for_virtual_device(char const *syspath,
>  {
>      DIR *dir;
>      char *dirpath;
> -    struct dirent entry, *result;
> +    struct dirent *entry;
>  
>      dirpath = g_strdup_printf("%s/slaves", syspath);
>      dir = opendir(dirpath);
> @@ -965,22 +965,24 @@ static void build_guest_fsinfo_for_virtual_device(char const *syspath,
>          g_free(dirpath);
>          return;
>      }
> -    g_free(dirpath);
>  
>      for (;;) {
> -        if (readdir_r(dir, &entry, &result) != 0) {
> -            error_setg_errno(errp, errno, "readdir_r(\"%s\")", dirpath);
> -            break;
> -        }
> -        if (!result) {
> +        errno = 0;
> +        entry = readdir(dir);
> +        if (entry == NULL) {
> +            if (errno) {
> +                error_setg_errno(errp, errno, "readdir(\"%s\")", dirpath);
> +            }
>              break;
>          }
>  
> -        if (entry.d_type == DT_LNK) {
> -            g_debug(" slave device '%s'", entry.d_name);
> -            dirpath = g_strdup_printf("%s/slaves/%s", syspath, entry.d_name);
> -            build_guest_fsinfo_for_device(dirpath, fs, errp);
> -            g_free(dirpath);
> +        if (entry->d_type == DT_LNK) {
> +            char *path;
> +
> +            g_debug(" slave device '%s'", entry->d_name);
> +            path = g_strdup_printf("%s/slaves/%s", syspath, entry->d_name);
> +            build_guest_fsinfo_for_device(path, fs, errp);
> +            g_free(path);
>  
>              if (*errp) {
>                  break;
> @@ -988,6 +990,7 @@ static void build_guest_fsinfo_for_virtual_device(char const *syspath,
>          }
>      }
>  
> +    g_free(dirpath);
>      closedir(dir);
>  }
>  
> 

Thanks,

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Michael Roth will pick this up.

Paolo