linux-user: don't short-circuit read with zero length

A zero-length read still needs to do the usual checks, thus it may return errors like EBADF. This makes the read syscall emulation consistent with the pread64 syscall emulation. Signed-off-by: Andreas Schwab <[email protected]> Reviewed-by: Laurent Vivier <[email protected]> Message-Id: <[email protected]> Signed-off-by: Laurent Vivier <[email protected]>
stefanha · Mar 7, 2019 · ba584f1 · ba584f1
1 parent 14c8a3a
commit ba584f1
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
@@ -7009,8 +7009,8 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
         _exit(arg1);
         return 0; /* avoid warning */
     case TARGET_NR_read:
-        if (arg3 == 0) {
-            return 0;
+        if (arg2 == 0 && arg3 == 0) {
+            return get_errno(safe_read(arg1, 0, 0));
         } else {
             if (!(p = lock_user(VERIFY_WRITE, arg2, arg3, 0)))
                 return -TARGET_EFAULT;