commit 7a16bdbb9ff4122af0a28dc20996c95352011fdd
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Wed Aug 29 16:36:44 2018 -0300

    Fix misreported errno on preadv2/pwritev2 (BZ#23579)
    
    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.

diff --git a/misc/tst-preadvwritev2-common.c b/misc/tst-preadvwritev2-common.c
index f889a21544947042..50b9da3fea56d288 100644
--- a/misc/tst-preadvwritev2-common.c
+++ b/misc/tst-preadvwritev2-common.c
@@ -19,9 +19,6 @@
 #include <limits.h>
 #include <support/check.h>
 
-static void
-do_test_with_invalid_flags (void)
-{
 #ifndef RWF_HIPRI
 # define RWF_HIPRI 0
 #endif
@@ -39,6 +36,68 @@ do_test_with_invalid_flags (void)
 #endif
 #define RWF_SUPPORTED	(RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT \
 			 | RWF_APPEND)
+
+static void
+do_test_with_invalid_fd (void)
+{
+  char buf[256];
+  struct iovec iov = { buf, sizeof buf };
+
+  /* Check with flag being 0 to use the fallback code which calls pwritev
+     or writev.  */
+  TEST_VERIFY (preadv2 (-1, &iov, 1, -1, 0) == -1);
+  TEST_COMPARE (errno, EBADF);
+  TEST_VERIFY (pwritev2 (-1, &iov, 1, -1, 0) == -1);
+  TEST_COMPARE (errno, EBADF);
+
+  /* Same tests as before but with flags being different than 0.  Since
+     there is no emulation for any flag value, fallback code returns
+     ENOTSUP.  This is different running on a kernel with preadv2/pwritev2
+     support, where EBADF is returned).  */
+  TEST_VERIFY (preadv2 (-1, &iov, 1, 0, RWF_HIPRI) == -1);
+  TEST_VERIFY (errno == EBADF || errno == ENOTSUP);
+  TEST_VERIFY (pwritev2 (-1, &iov, 1, 0, RWF_HIPRI) == -1);
+  TEST_VERIFY (errno == EBADF || errno == ENOTSUP);
+}
+
+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);
+  }
+}
+
+static void
+do_test_with_invalid_flags (void)
+{
   /* Set the next bit from the mask of all supported flags.  */
   int invalid_flag = RWF_SUPPORTED != 0 ? __builtin_clz (RWF_SUPPORTED) : 2;
   invalid_flag = 0x1 << ((sizeof (int) * CHAR_BIT) - invalid_flag);
diff --git a/misc/tst-preadvwritev2.c b/misc/tst-preadvwritev2.c
index be22802dbe00317f..cb58cbe41ecc639d 100644
--- a/misc/tst-preadvwritev2.c
+++ b/misc/tst-preadvwritev2.c
@@ -30,6 +30,8 @@ do_test (void)
 {
   do_test_with_invalid_flags ();
   do_test_without_offset ();
+  do_test_with_invalid_fd ();
+  do_test_with_invalid_iov ();
 
   return do_test_with_offset (0);
 }
diff --git a/misc/tst-preadvwritev64v2.c b/misc/tst-preadvwritev64v2.c
index 8d3cc32b284dbf4c..6a9de54c786acc53 100644
--- a/misc/tst-preadvwritev64v2.c
+++ b/misc/tst-preadvwritev64v2.c
@@ -32,6 +32,8 @@ do_test (void)
 {
   do_test_with_invalid_flags ();
   do_test_without_offset ();
+  do_test_with_invalid_fd ();
+  do_test_with_invalid_iov ();
 
   return do_test_with_offset (0);
 }
diff --git a/sysdeps/unix/sysv/linux/preadv2.c b/sysdeps/unix/sysv/linux/preadv2.c
index c8bf0764ef2629fc..bb08cbc5fd96962e 100644
--- a/sysdeps/unix/sysv/linux/preadv2.c
+++ b/sysdeps/unix/sysv/linux/preadv2.c
@@ -32,7 +32,7 @@ preadv2 (int fd, const struct iovec *vector, int count, off_t offset,
 # ifdef __NR_preadv2
   ssize_t result = SYSCALL_CANCEL (preadv2, fd, vector, count,
 				   LO_HI_LONG (offset), flags);
-  if (result >= 0)
+  if (result >= 0 || errno != ENOSYS)
     return result;
 # endif
   /* Trying to emulate the preadv2 syscall flags is troublesome:
diff --git a/sysdeps/unix/sysv/linux/preadv64v2.c b/sysdeps/unix/sysv/linux/preadv64v2.c
index d7400a0252a8c6a1..b72a047347b1db0e 100644
--- a/sysdeps/unix/sysv/linux/preadv64v2.c
+++ b/sysdeps/unix/sysv/linux/preadv64v2.c
@@ -30,7 +30,7 @@ preadv64v2 (int fd, const struct iovec *vector, int count, off64_t offset,
 #ifdef __NR_preadv64v2
   ssize_t result = SYSCALL_CANCEL (preadv64v2, fd, vector, count,
 				   LO_HI_LONG (offset), flags);
-  if (result >= 0)
+  if (result >= 0 || errno != ENOSYS)
     return result;
 #endif
   /* Trying to emulate the preadv2 syscall flags is troublesome:
diff --git a/sysdeps/unix/sysv/linux/pwritev2.c b/sysdeps/unix/sysv/linux/pwritev2.c
index 29c2264c8f3d949a..26333ebd43c5f0af 100644
--- a/sysdeps/unix/sysv/linux/pwritev2.c
+++ b/sysdeps/unix/sysv/linux/pwritev2.c
@@ -28,7 +28,7 @@ pwritev2 (int fd, const struct iovec *vector, int count, off_t offset,
 # ifdef __NR_pwritev2
   ssize_t result = SYSCALL_CANCEL (pwritev2, fd, vector, count,
 				   LO_HI_LONG (offset), flags);
-  if (result >= 0)
+  if (result >= 0 || errno != ENOSYS)
     return result;
 # endif
   /* Trying to emulate the pwritev2 syscall flags is troublesome:
diff --git a/sysdeps/unix/sysv/linux/pwritev64v2.c b/sysdeps/unix/sysv/linux/pwritev64v2.c
index 42da321149bce40d..17ea905aa6a8db94 100644
--- a/sysdeps/unix/sysv/linux/pwritev64v2.c
+++ b/sysdeps/unix/sysv/linux/pwritev64v2.c
@@ -30,7 +30,7 @@ pwritev64v2 (int fd, const struct iovec *vector, int count, off64_t offset,
 #ifdef __NR_pwritev64v2
   ssize_t result = SYSCALL_CANCEL (pwritev64v2, fd, vector, count,
 				   LO_HI_LONG (offset), flags);
-  if (result >= 0)
+  if (result >= 0 || errno != ENOSYS)
     return result;
 #endif
   /* Trying to emulate the pwritev2 syscall flags is troublesome:
