[02/11] nss_compat: Do not use mmap to read database files (bug 26258)

  This avoids crashes in case the files are truncated for some reason.
For typically file sizes, it is also going to be slightly faster.
Using __nss_files_fopen instead mirrors what nss_files does.
---
 nss/nss_compat/compat-grp.c        | 6 ++----
 nss/nss_compat/compat-initgroups.c | 6 ++----
 nss/nss_compat/compat-pwd.c        | 6 ++----
 nss/nss_compat/compat-spwd.c       | 6 ++----
 4 files changed, 8 insertions(+), 16 deletions(-)
  

On 7/17/20 4:30 AM, Florian Weimer via Libc-alpha wrote:
> This avoids crashes in case the files are truncated for some reason.
> For typically file sizes, it is also going to be slightly faster.
> Using __nss_files_fopen instead mirrors what nss_files does.

OK for 2.32.

Correct, using __nss_files_fopen activates the handle resulting in
use of the underlying caches.

Tested-by: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> ---
>  nss/nss_compat/compat-grp.c        | 6 ++----
>  nss/nss_compat/compat-initgroups.c | 6 ++----
>  nss/nss_compat/compat-pwd.c        | 6 ++----
>  nss/nss_compat/compat-spwd.c       | 6 ++----
>  4 files changed, 8 insertions(+), 16 deletions(-)
> 
> diff --git a/nss/nss_compat/compat-grp.c b/nss/nss_compat/compat-grp.c
> index d4f750b95c..510d49e8c7 100644
> --- a/nss/nss_compat/compat-grp.c
> +++ b/nss/nss_compat/compat-grp.c
> @@ -26,6 +26,7 @@
>  #include <string.h>
>  #include <libc-lock.h>
>  #include <kernel-features.h>
> +#include <nss_files.h>

OK.

>  
>  NSS_DECLARE_MODULE_FUNCTIONS (compat)
>  
> @@ -108,13 +109,10 @@ internal_setgrent (ent_t *ent, int stayopen, int needent)
>  
>    if (ent->stream == NULL)
>      {
> -      ent->stream = fopen ("/etc/group", "rme");
> +      ent->stream = __nss_files_fopen ("/etc/group");
>  
>        if (ent->stream == NULL)
>  	status = errno == EAGAIN ? NSS_STATUS_TRYAGAIN : NSS_STATUS_UNAVAIL;
> -      else
> -	/* We take care of locking ourself.  */
> -	__fsetlocking (ent->stream, FSETLOCKING_BYCALLER);
>      }
>    else
>      rewind (ent->stream);
> diff --git a/nss/nss_compat/compat-initgroups.c b/nss/nss_compat/compat-initgroups.c
> index 3671bef48b..c0dcdf839d 100644
> --- a/nss/nss_compat/compat-initgroups.c
> +++ b/nss/nss_compat/compat-initgroups.c
> @@ -29,6 +29,7 @@
>  #include <libc-lock.h>
>  #include <kernel-features.h>
>  #include <scratch_buffer.h>
> +#include <nss_files.h>
>  
>  NSS_DECLARE_MODULE_FUNCTIONS (compat)
>  
> @@ -122,13 +123,10 @@ internal_setgrent (ent_t *ent)
>    else
>      ent->blacklist.current = 0;
>  
> -  ent->stream = fopen ("/etc/group", "rme");
> +  ent->stream = __nss_files_fopen ("/etc/group");
>  
>    if (ent->stream == NULL)
>      status = errno == EAGAIN ? NSS_STATUS_TRYAGAIN : NSS_STATUS_UNAVAIL;
> -  else
> -    /* We take care of locking ourself.  */
> -    __fsetlocking (ent->stream, FSETLOCKING_BYCALLER);
>  
>    return status;
>  }
> diff --git a/nss/nss_compat/compat-pwd.c b/nss/nss_compat/compat-pwd.c
> index 394e39b811..3a212a0dab 100644
> --- a/nss/nss_compat/compat-pwd.c
> +++ b/nss/nss_compat/compat-pwd.c
> @@ -27,6 +27,7 @@
>  #include <string.h>
>  #include <libc-lock.h>
>  #include <kernel-features.h>
> +#include <nss_files.h>
>  
>  #include "netgroup.h"
>  #include "nisdomain.h"
> @@ -223,13 +224,10 @@ internal_setpwent (ent_t *ent, int stayopen, int needent)
>  
>    if (ent->stream == NULL)
>      {
> -      ent->stream = fopen ("/etc/passwd", "rme");
> +      ent->stream = __nss_files_fopen ("/etc/passwd");
>  
>        if (ent->stream == NULL)
>  	status = errno == EAGAIN ? NSS_STATUS_TRYAGAIN : NSS_STATUS_UNAVAIL;
> -      else
> -	/* We take care of locking ourself.  */
> -	__fsetlocking (ent->stream, FSETLOCKING_BYCALLER);
>      }
>    else
>      rewind (ent->stream);
> diff --git a/nss/nss_compat/compat-spwd.c b/nss/nss_compat/compat-spwd.c
> index ec5bf283cd..d802ee0302 100644
> --- a/nss/nss_compat/compat-spwd.c
> +++ b/nss/nss_compat/compat-spwd.c
> @@ -27,6 +27,7 @@
>  #include <string.h>
>  #include <libc-lock.h>
>  #include <kernel-features.h>
> +#include <nss_files.h>
>  
>  #include "netgroup.h"
>  #include "nisdomain.h"
> @@ -179,13 +180,10 @@ internal_setspent (ent_t *ent, int stayopen, int needent)
>  
>    if (ent->stream == NULL)
>      {
> -      ent->stream = fopen ("/etc/shadow", "rme");
> +      ent->stream = __nss_files_fopen ("/etc/shadow");
>  
>        if (ent->stream == NULL)
>  	status = errno == EAGAIN ? NSS_STATUS_TRYAGAIN : NSS_STATUS_UNAVAIL;
> -      else
> -	/* We take care of locking ourself.  */
> -	__fsetlocking (ent->stream, FSETLOCKING_BYCALLER);
>      }
>    else
>      rewind (ent->stream);
>