Linux: Use faccessat2 to implement faccessat (bug 18683)

Message ID 877dual7ex.fsf@oldenburg2.str.redhat.com
State New
Headers show
Series
  • Linux: Use faccessat2 to implement faccessat (bug 18683)
Related show

Commit Message

Vitaly Buka via Libc-alpha Aug. 7, 2020, 4:58 p.m.
This provides correct AT_EACCESS handling and also takes
Linux security modules into account.

Tested on i686-linux-gnu, x86_64-linux-gnu.  Built with
build-many-glibcs.py.

---
 sysdeps/unix/sysv/linux/faccessat.c       | 14 +++++++++++---
 sysdeps/unix/sysv/linux/kernel-features.h |  8 ++++++++
 2 files changed, 19 insertions(+), 3 deletions(-)

Comments

Vitaly Buka via Libc-alpha Aug. 7, 2020, 7:58 p.m. | #1
On 07/08/2020 13:58, Florian Weimer via Libc-alpha wrote:
> This provides correct AT_EACCESS handling and also takes

> Linux security modules into account.

> 

> Tested on i686-linux-gnu, x86_64-linux-gnu.  Built with

> build-many-glibcs.py.


LGTM, thanks.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>


> 

> ---

>  sysdeps/unix/sysv/linux/faccessat.c       | 14 +++++++++++---

>  sysdeps/unix/sysv/linux/kernel-features.h |  8 ++++++++

>  2 files changed, 19 insertions(+), 3 deletions(-)

> 

> diff --git a/sysdeps/unix/sysv/linux/faccessat.c b/sysdeps/unix/sysv/linux/faccessat.c

> index e4f18ab2db..56cb6dcc8b 100644

> --- a/sysdeps/unix/sysv/linux/faccessat.c

> +++ b/sysdeps/unix/sysv/linux/faccessat.c

> @@ -30,6 +30,13 @@

>  int

>  faccessat (int fd, const char *file, int mode, int flag)

>  {

> +  int ret = INLINE_SYSCALL_CALL (faccessat2, fd, file, mode, flag);

> +#if __ASSUME_FACCESSAT2

> +  return ret;

> +#else

> +  if (ret == 0 || errno != ENOSYS)

> +    return ret;

> +

>    if (flag & ~(AT_SYMLINK_NOFOLLOW | AT_EACCESS))

>      return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);

>  


Ok.

> @@ -41,9 +48,9 @@ faccessat (int fd, const char *file, int mode, int flag)

>      return -1;

>  

>    mode &= (X_OK | W_OK | R_OK);	/* Clear any bogus bits. */

> -#if R_OK != S_IROTH || W_OK != S_IWOTH || X_OK != S_IXOTH

> -# error Oops, portability assumptions incorrect.

> -#endif

> +# if R_OK != S_IROTH || W_OK != S_IWOTH || X_OK != S_IXOTH

> +#  error Oops, portability assumptions incorrect.

> +# endif

>  

>    if (mode == F_OK)

>      return 0;			/* The file exists. */


Ok.

> @@ -68,4 +75,5 @@ faccessat (int fd, const char *file, int mode, int flag)

>      return 0;

>  

>    return INLINE_SYSCALL_ERROR_RETURN_VALUE (EACCES);

> +#endif /* !__ASSUME_FACCESSAT2 */

>  }


Ok.

> diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h

> index 32533e94cf..a6bbc3c94e 100644

> --- a/sysdeps/unix/sysv/linux/kernel-features.h

> +++ b/sysdeps/unix/sysv/linux/kernel-features.h

> @@ -214,4 +214,12 @@

>  # define __ASSUME_WAITID_PID0_P_PGID

>  #endif

>  

> +/* The faccessat2 system call was introduced across all architectures

> +   in Linux 5.8.  */

> +#if __LINUX_KERNEL_VERSION >= 0x050800

> +# define __ASSUME_FACCESSAT2 1

> +#else

> +# define __ASSUME_FACCESSAT2 0

> +#endif

> +

>  #endif /* kernel-features.h */

> 


Ok.

Patch

diff --git a/sysdeps/unix/sysv/linux/faccessat.c b/sysdeps/unix/sysv/linux/faccessat.c
index e4f18ab2db..56cb6dcc8b 100644
--- a/sysdeps/unix/sysv/linux/faccessat.c
+++ b/sysdeps/unix/sysv/linux/faccessat.c
@@ -30,6 +30,13 @@ 
 int
 faccessat (int fd, const char *file, int mode, int flag)
 {
+  int ret = INLINE_SYSCALL_CALL (faccessat2, fd, file, mode, flag);
+#if __ASSUME_FACCESSAT2
+  return ret;
+#else
+  if (ret == 0 || errno != ENOSYS)
+    return ret;
+
   if (flag & ~(AT_SYMLINK_NOFOLLOW | AT_EACCESS))
     return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
 
@@ -41,9 +48,9 @@  faccessat (int fd, const char *file, int mode, int flag)
     return -1;
 
   mode &= (X_OK | W_OK | R_OK);	/* Clear any bogus bits. */
-#if R_OK != S_IROTH || W_OK != S_IWOTH || X_OK != S_IXOTH
-# error Oops, portability assumptions incorrect.
-#endif
+# if R_OK != S_IROTH || W_OK != S_IWOTH || X_OK != S_IXOTH
+#  error Oops, portability assumptions incorrect.
+# endif
 
   if (mode == F_OK)
     return 0;			/* The file exists. */
@@ -68,4 +75,5 @@  faccessat (int fd, const char *file, int mode, int flag)
     return 0;
 
   return INLINE_SYSCALL_ERROR_RETURN_VALUE (EACCES);
+#endif /* !__ASSUME_FACCESSAT2 */
 }
diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h
index 32533e94cf..a6bbc3c94e 100644
--- a/sysdeps/unix/sysv/linux/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -214,4 +214,12 @@ 
 # define __ASSUME_WAITID_PID0_P_PGID
 #endif
 
+/* The faccessat2 system call was introduced across all architectures
+   in Linux 5.8.  */
+#if __LINUX_KERNEL_VERSION >= 0x050800
+# define __ASSUME_FACCESSAT2 1
+#else
+# define __ASSUME_FACCESSAT2 0
+#endif
+
 #endif /* kernel-features.h */