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From: Aurelien Jarno <aurelien@aurel32.net>
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Date: Fri, 30 Jan 2009 19:48:17 +0000
Subject: [Qemu-devel] [6481] linuw-user fix: read() and acct() on NULL
	arguments
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Revision: 6481
          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=6481
Author:   aurel32
Date:     2009-01-30 19:48:17 +0000 (Fri, 30 Jan 2009)

Log Message:
-----------
linuw-user fix: read() and acct() on NULL arguments

Returning efault in these cases is not correct. Originally
proposed by Thayne Harbaugh in 2007:
http://www.mail-archive.com/qemu-devel@nongnu.org/msg14658.html

Signed-off-by: Riku Voipio <riku.voipio@iki.fi>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

Modified Paths:
--------------
    trunk/linux-user/syscall.c

Modified: trunk/linux-user/syscall.c
===================================================================
--- trunk/linux-user/syscall.c	2009-01-30 19:48:07 UTC (rev 6480)
+++ trunk/linux-user/syscall.c	2009-01-30 19:48:17 UTC (rev 6481)
@@ -3437,10 +3437,14 @@
         ret = 0; /* avoid warning */
         break;
     case TARGET_NR_read:
-        if (!(p = lock_user(VERIFY_WRITE, arg2, arg3, 0)))
-            goto efault;
-        ret = get_errno(read(arg1, p, arg3));
-        unlock_user(p, arg2, ret);
+        if (arg3 == 0)
+            ret = 0;
+        else {
+            if (!(p = lock_user(VERIFY_WRITE, arg2, arg3, 0)))
+                goto efault;
+            ret = get_errno(read(arg1, p, arg3));
+            unlock_user(p, arg2, ret);
+        }
         break;
     case TARGET_NR_write:
         if (!(p = lock_user(VERIFY_READ, arg2, arg3, 1)))
@@ -3941,10 +3945,14 @@
         goto unimplemented;
 #endif
     case TARGET_NR_acct:
-        if (!(p = lock_user_string(arg1)))
-            goto efault;
-        ret = get_errno(acct(path(p)));
-        unlock_user(p, arg1, 0);
+        if (arg1 == 0) {
+            ret = get_errno(acct(NULL));
+        } else {
+            if (!(p = lock_user_string(arg1)))
+                goto efault;
+            ret = get_errno(acct(path(p)));
+            unlock_user(p, arg1, 0);
+        }
         break;
 #ifdef TARGET_NR_umount2 /* not on alpha */
     case TARGET_NR_umount2: