Re: [PATCH] Fix misreported errno on preadv2/pwritev2 (BZ#23579)

[Szabolcs Nagy <Szabolcs dot Nagy at arm dot com>]

On 29/08/18 22:20, Adhemerval Zanella wrote:
> The fallback code of Linux wrapper for preadv2/pwritev2 executes
> regardless of the errno code for preadv2, instead of the case where
> the syscall is not supported.
> 
> This fixes it by calling the fallback code iff errno is ENOSYS. The
> patch also adds tests for both invalid file descriptor and invalid
> iov_len and vector count.
> 
> The only discrepancy between preadv2 and fallback code regarding
> error reporting is when an invalid flags are used.  The fallback code
> bails out earlier with ENOTSUP instead of EINVAL/EBADF when the syscall
> is used.
> 
> Checked on x86_64-linux-gnu on a 4.4.0 and 4.15.0 kernel.
> 
> 	[BZ #23579]
> 	* misc/tst-preadvwritev2-common.c (do_test_with_invalid_fd): New
> 	test.
> 	* misc/tst-preadvwritev2.c, misc/tst-preadvwritev64v2.c (do_test):
> 	Call do_test_with_invalid_fd.
> 	* sysdeps/unix/sysv/linux/preadv2.c (preadv2): Use fallback code iff
> 	errno is ENOSYS.
> 	* sysdeps/unix/sysv/linux/preadv64v2.c (preadv64v2): Likewise.
> 	* sysdeps/unix/sysv/linux/pwritev2.c (pwritev2): Likewise.
> 	* sysdeps/unix/sysv/linux/pwritev64v2.c (pwritev64v2): Likewise.


with build-many-glibcs.py in
logs/glibcs/i686-gnu/010-glibcs-i686-gnu-check-log.txt i see

In file included from tst-preadvwritev2.c:26:
tst-preadvwritev2-common.c: In function ‘do_test_with_invalid_iov’:
tst-preadvwritev2-common.c:89:22: error: ‘IOV_MAX’ undeclared (first use in this function); did you mean ‘INT_MAX’?
     struct iovec iov[IOV_MAX+1] = { 0 };
                      ^~~~~~~
                      INT_MAX
tst-preadvwritev2-common.c:89:22: note: each undeclared identifier is reported only once for each function it appears in
tst-preadvwritev2-common.c:89:18: error: unused variable ‘iov’ [-Werror=unused-variable]
     struct iovec iov[IOV_MAX+1] = { 0 };
                  ^~~
cc1: all warnings being treated as errors
make[3]: *** [../o-iterator.mk:9: /data/glibc-build-j2/build/glibcs/i686-gnu/glibc/misc/tst-preadvwritev2.o] Error 1

...
> +static void
> +do_test_with_invalid_iov (void)
> +{
> +  {
> +    char buf[256];
> +    struct iovec iov;
> +
> +    iov.iov_base = buf;
> +    iov.iov_len = (size_t)SSIZE_MAX + 1;
> +
> +    TEST_VERIFY (preadv2 (temp_fd, &iov, 1, 0, 0) == -1);
> +    TEST_COMPARE (errno, EINVAL);
> +    TEST_VERIFY (pwritev2 (temp_fd, &iov, 1, 0, 0) == -1);
> +    TEST_COMPARE (errno, EINVAL);
> +
> +    /* Same as for invalid file descriptor tests, emulation fallback
> +       first checks for flag value and return ENOTSUP.  */
> +    TEST_VERIFY (preadv2 (temp_fd, &iov, 1, 0, RWF_HIPRI) == -1);
> +    TEST_VERIFY (errno == EINVAL || errno == ENOTSUP);
> +    TEST_VERIFY (pwritev2 (temp_fd, &iov, 1, 0, RWF_HIPRI) == -1);
> +    TEST_VERIFY (errno == EINVAL || errno == ENOTSUP);
> +  }
> +
> +  {
> +    /* An invalid iovec buffer should trigger an invalid memory access
> +       or an error (Linux for instance returns EFAULT).  */
> +    struct iovec iov[IOV_MAX+1] = { 0 };
> +
> +    TEST_VERIFY (preadv2 (temp_fd, iov, IOV_MAX + 1, 0, RWF_HIPRI) == -1);
> +    TEST_VERIFY (errno == EINVAL || errno == ENOTSUP);
> +    TEST_VERIFY (pwritev2 (temp_fd, iov, IOV_MAX + 1, 0, RWF_HIPRI) == -1);
> +    TEST_VERIFY (errno == EINVAL || errno == ENOTSUP);
> +  }
> +}