preadv2/pwritev2: Handle offset == -1 [BZ #22753]

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

(cherry picked from commit d4b4a00a462348750bb18544eb30853ee6ac5d10)

14 files changed, 105 insertions, 15 deletions

diff --git a/ChangeLog b/ChangeLog
index 6848c7d550..4baa85bcfc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,20 @@
+2018-09-28  Florian Weimer  <fweimer@redhat.com>
+
+	[BZ #22753]
+	* sysdeps/posix/preadv2.c (preadv2): Handle offset == -1.
+	* sysdeps/posix/preadv64v2.c (preadv64v2): Likewise.
+	* sysdeps/posix/pwritev2.c (pwritev2): Likewise.
+	* sysdeps/posix/pwritev64v2.c (pwritev64v2): Likweise.
+	* sysdeps/unix/sysv/linux/preadv2.c (preadv2): Likewise.
+	* sysdeps/unix/sysv/linux/preadv64v2.c (preadv64v2): Likewise.
+	* sysdeps/unix/sysv/linux/pwritev2.c (pwritev2): Likewise.
+	* sysdeps/unix/sysv/linux/pwritev64v2.c (pwritev64v2): Likweise.
+	* manual/llio.texi (Scatter-Gather): Mention offset -1.
+	* misc/tst-preadvwritev-common.c (do_test_without_offset): New.
+	* misc/tst-preadvwritev2.c (do_test): Call it.
+	* misc/tst-preadvwritev64v2.c (do_test): Likewise.
+	* NEWS: Add bug fixed.
+
 2018-09-06  Stefan Liebler  <stli@linux.ibm.com>
 
 	* sysdeps/unix/sysv/linux/spawni.c (maybe_script_execute):
diff --git a/NEWS b/NEWS
index a868a652f7..d5e3403e8b 100644
--- a/NEWS
+++ b/NEWS
@@ -135,6 +135,7 @@ The following bugs are resolved with this release:
     (CVE-2018-1000001)
   [22685] powerpc: Fix syscalls during early process initialization
   [22715] x86-64: Properly align La_x86_64_retval to VEC_SIZE
+  [22753] libc: preadv2/pwritev2 fallback code should handle offset=-1
   [22774] malloc: Integer overflow in malloc (CVE-2018-6551)
   [22786] Fix path length overflow in realpath
   [23005] resolv: Fix crash in resolver on memory allocation failure
diff --git a/manual/llio.texi b/manual/llio.texi
index e72c53c785..4ce9ee360e 100644
--- a/manual/llio.texi
+++ b/manual/llio.texi
@@ -754,9 +754,13 @@ When the source file is compiled using @code{_FILE_OFFSET_BITS == 64} on a
 @c This is a syscall for Linux v4.6.  The sysdeps/posix fallback emulation
 @c is also MT-Safe since it calls preadv.
 
-This function is similar to the @code{preadv} function, with the difference
-it adds an extra @var{flags} parameter of type @code{int}.  The supported
-@var{flags} are dependent of the underlying system.  For Linux it supports:
+This function is similar to the @code{preadv} function, with the
+difference it adds an extra @var{flags} parameter of type @code{int}.
+Additionally, if @var{offset} is @math{-1}, the current file position
+is used and updated (like the @code{readv} function).
+
+The supported @var{flags} are dependent of the underlying system.  For
+Linux it supports:
 
 @vtable @code
 @item RWF_HIPRI
@@ -823,10 +827,13 @@ When the source file is compiled using @code{_FILE_OFFSET_BITS == 64} on a
 @c This is a syscall for Linux v4.6.  The sysdeps/posix fallback emulation
 @c is also MT-Safe since it calls pwritev.
 
-This function is similar to the @code{pwritev} function, with the difference
-it adds an extra @var{flags} parameter of type @code{int}.  The supported
-@var{flags} are dependent of the underlying system and for Linux it supports
-the same ones as for @code{preadv2}.
+This function is similar to the @code{pwritev} function, with the
+difference it adds an extra @var{flags} parameter of type @code{int}.
+Additionally, if @var{offset} is @math{-1}, the current file position
+should is used and updated (like the @code{writev} function).
+
+The supported @var{flags} are dependent of the underlying system.  For
+Linux, the supported flags are the same as those for @code{preadv2}.
 
 When the source file is compiled with @code{_FILE_OFFSET_BITS == 64} the
 @code{pwritev2} function is in fact @code{pwritev64v2} and the type
diff --git a/misc/tst-preadvwritev-common.c b/misc/tst-preadvwritev-common.c
index 676d4953ac..7f9a63f1f5 100644
--- a/misc/tst-preadvwritev-common.c
+++ b/misc/tst-preadvwritev-common.c
@@ -16,6 +16,7 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#include <array_length.h>
 #include <stdio.h>
 #include <stdint.h>
 #include <errno.h>
@@ -25,6 +26,7 @@
 
 #include <support/check.h>
 #include <support/temp_file.h>
+#include <support/xunistd.h>
 
 static char *temp_filename;
 static int temp_fd;
@@ -50,6 +52,42 @@ do_prepare (int argc, char **argv)
   pwritev (__fd, __iov, __iovcnt, __offset)
 #endif
 
+static __attribute__ ((unused)) void
+do_test_without_offset (void)
+{
+  xftruncate (temp_fd, 0);
+
+  xwrite (temp_fd, "123", 3);
+  xlseek (temp_fd, 2, SEEK_SET);
+  {
+    struct iovec iov[] =
+      {
+        { (void *) "abc", 3 },
+        { (void *) "xyzt", 4 },
+      };
+    TEST_COMPARE (PWRITEV (temp_fd, iov, array_length (iov), -1), 7);
+  }
+  TEST_COMPARE (xlseek (temp_fd, 0, SEEK_CUR), 9);
+
+  xlseek (temp_fd, 1, SEEK_SET);
+  char buf1[3];
+  char buf2[2];
+  {
+    struct iovec iov[] =
+      {
+        { buf1, sizeof (buf1) },
+        { buf2, sizeof (buf2) },
+      };
+    TEST_COMPARE (PREADV (temp_fd, iov, array_length (iov), -1),
+                  sizeof (buf1) + sizeof (buf2));
+    TEST_COMPARE (memcmp ("2ab", buf1, sizeof (buf1)), 0);
+    TEST_COMPARE (memcmp ("cx", buf2, sizeof (buf2)), 0);
+    TEST_COMPARE (xlseek (temp_fd, 0, SEEK_CUR), 6);
+  }
+
+  xftruncate (temp_fd, 0);
+}
+
 static int
 do_test_with_offset (off_t offset)
 {
diff --git a/misc/tst-preadvwritev2.c b/misc/tst-preadvwritev2.c
index 682c7579da..225f5e59c1 100644
--- a/misc/tst-preadvwritev2.c
+++ b/misc/tst-preadvwritev2.c
@@ -29,6 +29,7 @@ static int
 do_test (void)
 {
   do_test_with_invalid_flags ();
+  do_test_without_offset ();
 
   return do_test_with_offset (0);
 }
diff --git a/misc/tst-preadvwritev64v2.c b/misc/tst-preadvwritev64v2.c
index 9ddc7625f0..facdbdca61 100644
--- a/misc/tst-preadvwritev64v2.c
+++ b/misc/tst-preadvwritev64v2.c
@@ -31,6 +31,7 @@ static int
 do_test (void)
 {
   do_test_with_invalid_flags ();
+  do_test_without_offset ();
 
   return do_test_with_offset (0);
 }
diff --git a/sysdeps/posix/preadv2.c b/sysdeps/posix/preadv2.c
index d27f7028ed..fe73d3cbea 100644
--- a/sysdeps/posix/preadv2.c
+++ b/sysdeps/posix/preadv2.c
@@ -32,7 +32,10 @@ preadv2 (int fd, const struct iovec *vector, int count, OFF_T offset,
       return -1;
     }
 
-  return preadv (fd, vector, count, offset);
+  if (offset == -1)
+    return __readv (fd, vector, count);
+  else
+    return preadv (fd, vector, count, offset);
 }
 
 #endif
diff --git a/sysdeps/posix/preadv64v2.c b/sysdeps/posix/preadv64v2.c
index ce7cb40bf2..8569c8b398 100644
--- a/sysdeps/posix/preadv64v2.c
+++ b/sysdeps/posix/preadv64v2.c
@@ -29,7 +29,10 @@ preadv64v2 (int fd, const struct iovec *vector, int count, OFF_T offset,
       return -1;
     }
 
-  return preadv64 (fd, vector, count, offset);
+  if (offset == -1)
+    return __readv (fd, vector, count);
+  else
+    return preadv64 (fd, vector, count, offset);
 }
 
 #ifdef __OFF_T_MATCHES_OFF64_T
diff --git a/sysdeps/posix/pwritev2.c b/sysdeps/posix/pwritev2.c
index 7ec8cbc407..b24b491a81 100644
--- a/sysdeps/posix/pwritev2.c
+++ b/sysdeps/posix/pwritev2.c
@@ -32,7 +32,10 @@ pwritev2 (int fd, const struct iovec *vector, int count, OFF_T offset,
       return -1;
     }
 
-  return pwritev (fd, vector, count, offset);
+  if (offset == -1)
+    return __writev (fd, vector, count);
+  else
+    return pwritev (fd, vector, count, offset);
 }
 
 #endif
diff --git a/sysdeps/posix/pwritev64v2.c b/sysdeps/posix/pwritev64v2.c
index be98aeed9d..ae4c4284c2 100644
--- a/sysdeps/posix/pwritev64v2.c
+++ b/sysdeps/posix/pwritev64v2.c
@@ -30,7 +30,10 @@ pwritev64v2 (int fd, const struct iovec *vector, int count, OFF_T offset,
       return -1;
     }
 
-  return pwritev64 (fd, vector, count, offset);
+  if (offset == -1)
+    return __writev (fd, vector, count);
+  else
+    return pwritev64 (fd, vector, count, offset);
 }
 
 #ifdef __OFF_T_MATCHES_OFF64_T
diff --git a/sysdeps/unix/sysv/linux/preadv2.c b/sysdeps/unix/sysv/linux/preadv2.c
index 137e2dd791..a7a3aeeee6 100644
--- a/sysdeps/unix/sysv/linux/preadv2.c
+++ b/sysdeps/unix/sysv/linux/preadv2.c
@@ -49,7 +49,10 @@ preadv2 (int fd, const struct iovec *vector, int count, off_t offset,
       __set_errno (ENOTSUP);
       return -1;
     }
-  return preadv (fd, vector, count, offset);
+  if (offset == -1)
+    return __readv (fd, vector, count);
+  else
+    return preadv (fd, vector, count, offset);
 }
 
 #endif
diff --git a/sysdeps/unix/sysv/linux/preadv64v2.c b/sysdeps/unix/sysv/linux/preadv64v2.c
index 8f413253f4..53c946861c 100644
--- a/sysdeps/unix/sysv/linux/preadv64v2.c
+++ b/sysdeps/unix/sysv/linux/preadv64v2.c
@@ -47,7 +47,11 @@ preadv64v2 (int fd, const struct iovec *vector, int count, off64_t offset,
       __set_errno (ENOTSUP);
       return -1;
     }
-  return preadv64 (fd, vector, count, offset);
+
+  if (offset == -1)
+    return __readv (fd, vector, count);
+  else
+    return preadv64 (fd, vector, count, offset);
 }
 
 #ifdef __OFF_T_MATCHES_OFF64_T
diff --git a/sysdeps/unix/sysv/linux/pwritev2.c b/sysdeps/unix/sysv/linux/pwritev2.c
index 8e5032fe2f..17677df98d 100644
--- a/sysdeps/unix/sysv/linux/pwritev2.c
+++ b/sysdeps/unix/sysv/linux/pwritev2.c
@@ -45,7 +45,10 @@ pwritev2 (int fd, const struct iovec *vector, int count, off_t offset,
       __set_errno (ENOTSUP);
       return -1;
     }
-  return pwritev (fd, vector, count, offset);
+  if (offset == -1)
+    return __writev (fd, vector, count);
+  else
+    return pwritev (fd, vector, count, offset);
 }
 
 #endif
diff --git a/sysdeps/unix/sysv/linux/pwritev64v2.c b/sysdeps/unix/sysv/linux/pwritev64v2.c
index d2800c6657..f5753eede5 100644
--- a/sysdeps/unix/sysv/linux/pwritev64v2.c
+++ b/sysdeps/unix/sysv/linux/pwritev64v2.c
@@ -47,7 +47,10 @@ pwritev64v2 (int fd, const struct iovec *vector, int count, off64_t offset,
       __set_errno (ENOTSUP);
       return -1;
     }
-  return pwritev64 (fd, vector, count, offset);
+  if (offset == -1)
+    return __writev (fd, vector, count);
+  else
+    return pwritev64 (fd, vector, count, offset);
 }
 
 #ifdef __OFF_T_MATCHES_OFF64_T