diff mbox

[PULL,v3,21/22] linux-user: writev Partial Writes

Message ID 29560a6cb7a7a705de3d7dfb44e8b1c0a12ad37d.1408712881.git.riku.voipio@linaro.org
State New
Headers show

Commit Message

Riku Voipio Aug. 22, 2014, 1:24 p.m. UTC 
From: Tom Musta <tommusta@gmail.com>

Although not technically not required by POSIX, the writev system call will
typically write out its buffers individually.  That is, if the first buffer
is written successfully, but the second buffer pointer is invalid, then
the first chuck will be written and its size is returned.

Signed-off-by: Tom Musta <tommusta@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
---
 linux-user/syscall.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)
diff mbox

Patch

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 1da216e..ebdc70e 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -1803,6 +1803,7 @@  static struct iovec *lock_iovec(int type, abi_ulong target_addr,
     abi_ulong total_len, max_len;
     int i;
     int err = 0;
+    bool bad_address = false;
 
     if (count == 0) {
         errno = 0;
@@ -1843,9 +1844,20 @@  static struct iovec *lock_iovec(int type, abi_ulong target_addr,
             vec[i].iov_base = 0;
         } else {
             vec[i].iov_base = lock_user(type, base, len, copy);
+            /* If the first buffer pointer is bad, this is a fault.  But
+             * subsequent bad buffers will result in a partial write; this
+             * is realized by filling the vector with null pointers and
+             * zero lengths. */
             if (!vec[i].iov_base) {
-                err = EFAULT;
-                goto fail;
+                if (i == 0) {
+                    err = EFAULT;
+                    goto fail;
+                } else {
+                    bad_address = true;
+                }
+            }
+            if (bad_address) {
+                len = 0;
             }
             if (len > max_len - total_len) {
                 len = max_len - total_len;