[Qemu-devel] [PATCH] fix read() and acct() on NULL arguments

[Riku Voipio <riku.voipio@iki.fi>]

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>
---
 linux-user/syscall.c |   24 ++++++++++++++++--------
 1 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 4eb003a..ab81b3a 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -3713,10 +3713,14 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
         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)))
@@ -4217,10 +4221,14 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
         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:
-- 
1.5.6.5


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