diff mbox series

[v3] cdefs: Drop access attribute for _FORTIFY_SOURCE=3 (BZ #31383)

Message ID 20240226160344.3519392-1-siddhesh@sourceware.org
State Committed
Commit bf9688e623262c5fa9f91e4de0e84db45025076f
Headers
Series [v3] cdefs: Drop access attribute for _FORTIFY_SOURCE=3 (BZ #31383) |

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Commit Message

Siddhesh Poyarekar Feb. 26, 2024, 4:03 p.m. UTC 
  When passed a pointer to a zero-sized struct, the access attribute
without the third argument misleads -Wstringop-overflow diagnostics to
think that a function is writing 1 byte into the zero-sized structs.
The attribute doesn't add that much value in this context, so drop it
completely for _FORTIFY_SOURCE=3.

Resolves: BZ #31383
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
Changes from v2:
- Use supported-fortify to set the right fortification level for the
  compiler.

Changes from v1:
- Adjust test to read from /dev/zero

 io/Makefile        |  2 ++
 io/tst-read-zero.c | 39 +++++++++++++++++++++++++++++++++++++++
 misc/sys/cdefs.h   |  6 +++---
 3 files changed, 44 insertions(+), 3 deletions(-)
 create mode 100644 io/tst-read-zero.c

Comments

Adhemerval Zanella Netto Feb. 28, 2024, 1:23 p.m. UTC | #1 
On 26/02/24 13:03, Siddhesh Poyarekar wrote:
> When passed a pointer to a zero-sized struct, the access attribute
> without the third argument misleads -Wstringop-overflow diagnostics to
> think that a function is writing 1 byte into the zero-sized structs.
> The attribute doesn't add that much value in this context, so drop it
> completely for _FORTIFY_SOURCE=3.
> 
> Resolves: BZ #31383
> Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

LGTM, thanks.

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

> ---
> Changes from v2:
> - Use supported-fortify to set the right fortification level for the
>   compiler.
> 
> Changes from v1:
> - Adjust test to read from /dev/zero
> 
>  io/Makefile        |  2 ++
>  io/tst-read-zero.c | 39 +++++++++++++++++++++++++++++++++++++++
>  misc/sys/cdefs.h   |  6 +++---
>  3 files changed, 44 insertions(+), 3 deletions(-)
>  create mode 100644 io/tst-read-zero.c
> 
> diff --git a/io/Makefile b/io/Makefile
> index 54d950d51f..19932d50f7 100644
> --- a/io/Makefile
> +++ b/io/Makefile
> @@ -215,6 +215,7 @@ tests := \
>    tst-openat \
>    tst-posix_fallocate \
>    tst-posix_fallocate64 \
> +  tst-read-zero \
>    tst-readlinkat \
>    tst-renameat \
>    tst-stat \

Maybe it makes more sense to add this test on debug subfolder, but I don't
have a strong preference.

> @@ -290,6 +291,7 @@ CFLAGS-read.c += -fexceptions -fasynchronous-unwind-tables $(config-cflags-wno-i
>  CFLAGS-write.c += -fexceptions -fasynchronous-unwind-tables $(config-cflags-wno-ignored-attributes)
>  CFLAGS-close.c += -fexceptions -fasynchronous-unwind-tables
>  CFLAGS-lseek64.c += $(config-cflags-wno-ignored-attributes)
> +CFLAGS-tst-read-zero.c += $(no-fortify-source),-D_FORTIFY_SOURCE=$(supported-fortify)
>  
>  CFLAGS-test-stat.c += -D_FILE_OFFSET_BITS=64 -D_LARGEFILE64_SOURCE
>  CFLAGS-test-lfs.c += -D_LARGEFILE64_SOURCE
> diff --git a/io/tst-read-zero.c b/io/tst-read-zero.c
> new file mode 100644
> index 0000000000..8d1d30a543
> --- /dev/null
> +++ b/io/tst-read-zero.c
> @@ -0,0 +1,39 @@
> +/* read smoke test for 0-sized structures.
> +   Copyright The GNU Toolchain Authors.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +/* Zero-sized structures should not result in any overflow warnings or
> +   errors when fortification is enabled.  */
> +#include <fcntl.h>
> +#include <stdio.h>
> +#include <unistd.h>
> +#include <support/check.h>
> +
> +int
> +do_test (void)
> +{
> +  struct test_st {} test_info[16];
> +  int fd = open ("/dev/zero", O_RDONLY, 0);
> +
> +  if (fd == -1)
> +    FAIL_UNSUPPORTED ("Unable to open /dev/zero: %m");
> +
> +  TEST_VERIFY_EXIT (read (fd, test_info, sizeof(test_info)) == 0);
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>
> diff --git a/misc/sys/cdefs.h b/misc/sys/cdefs.h
> index 520231dbea..800c44640f 100644
> --- a/misc/sys/cdefs.h
> +++ b/misc/sys/cdefs.h
> @@ -683,10 +683,10 @@ _Static_assert (0, "IEEE 128-bits long double requires redirection on this platf
>  #  define __attr_access(x) __attribute__ ((__access__ x))
>  /* For _FORTIFY_SOURCE == 3 we use __builtin_dynamic_object_size, which may
>     use the access attribute to get object sizes from function definition
> -   arguments, so we can't use them on functions we fortify.  Drop the object
> -   size hints for such functions.  */
> +   arguments, so we can't use them on functions we fortify.  Drop the access
> +   attribute for such functions.  */
>  #  if __USE_FORTIFY_LEVEL == 3
> -#    define __fortified_attr_access(a, o, s) __attribute__ ((__access__ (a, o)))
> +#    define __fortified_attr_access(a, o, s)
>  #  else
>  #    define __fortified_attr_access(a, o, s) __attr_access ((a, o, s))
>  #  endif
diff mbox series

Patch

diff --git a/io/Makefile b/io/Makefile
index 54d950d51f..19932d50f7 100644
--- a/io/Makefile
+++ b/io/Makefile
@@ -215,6 +215,7 @@  tests := \
   tst-openat \
   tst-posix_fallocate \
   tst-posix_fallocate64 \
+  tst-read-zero \
   tst-readlinkat \
   tst-renameat \
   tst-stat \
@@ -290,6 +291,7 @@  CFLAGS-read.c += -fexceptions -fasynchronous-unwind-tables $(config-cflags-wno-i
 CFLAGS-write.c += -fexceptions -fasynchronous-unwind-tables $(config-cflags-wno-ignored-attributes)
 CFLAGS-close.c += -fexceptions -fasynchronous-unwind-tables
 CFLAGS-lseek64.c += $(config-cflags-wno-ignored-attributes)
+CFLAGS-tst-read-zero.c += $(no-fortify-source),-D_FORTIFY_SOURCE=$(supported-fortify)
 
 CFLAGS-test-stat.c += -D_FILE_OFFSET_BITS=64 -D_LARGEFILE64_SOURCE
 CFLAGS-test-lfs.c += -D_LARGEFILE64_SOURCE
diff --git a/io/tst-read-zero.c b/io/tst-read-zero.c
new file mode 100644
index 0000000000..8d1d30a543
--- /dev/null
+++ b/io/tst-read-zero.c
@@ -0,0 +1,39 @@ 
+/* read smoke test for 0-sized structures.
+   Copyright The GNU Toolchain Authors.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* Zero-sized structures should not result in any overflow warnings or
+   errors when fortification is enabled.  */
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <support/check.h>
+
+int
+do_test (void)
+{
+  struct test_st {} test_info[16];
+  int fd = open ("/dev/zero", O_RDONLY, 0);
+
+  if (fd == -1)
+    FAIL_UNSUPPORTED ("Unable to open /dev/zero: %m");
+
+  TEST_VERIFY_EXIT (read (fd, test_info, sizeof(test_info)) == 0);
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/misc/sys/cdefs.h b/misc/sys/cdefs.h
index 520231dbea..800c44640f 100644
--- a/misc/sys/cdefs.h
+++ b/misc/sys/cdefs.h
@@ -683,10 +683,10 @@  _Static_assert (0, "IEEE 128-bits long double requires redirection on this platf
 #  define __attr_access(x) __attribute__ ((__access__ x))
 /* For _FORTIFY_SOURCE == 3 we use __builtin_dynamic_object_size, which may
    use the access attribute to get object sizes from function definition
-   arguments, so we can't use them on functions we fortify.  Drop the object
-   size hints for such functions.  */
+   arguments, so we can't use them on functions we fortify.  Drop the access
+   attribute for such functions.  */
 #  if __USE_FORTIFY_LEVEL == 3
-#    define __fortified_attr_access(a, o, s) __attribute__ ((__access__ (a, o)))
+#    define __fortified_attr_access(a, o, s)
 #  else
 #    define __fortified_attr_access(a, o, s) __attr_access ((a, o, s))
 #  endif