linux-user: Allow getsockopt() with NULL optval address

Some programs test availability of socket options by asking for the
value with an NULL optval address, which currenrly always trigger an
EFAULT in qemu.  Fix it by allowing a NULL address, in the same manner
as the Linux kernel on physical machines.

Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/2390
Signed-off-by: Helge Deller <deller@gmx.de>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com>

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 4594909242e3c014ac3833136a7b73d3fbfdf406..d68edb7afd7c5afae32c0285892d8d3169c88319 100644 (file)
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -2644,6 +2644,10 @@ get_timeout:
             if (ret < 0) {
                 return ret;
             }
+            /* special case: destination address is NULL, return 0 */
+            if (optval_addr) {
+                len = 0;
+            }
             if (len == sizeof(struct target__kernel_sock_timeval)) {
                 if (copy_to_user_timeval64(optval_addr, &tv)) {
                     return -TARGET_EFAULT;
@@ -2844,7 +2848,10 @@ get_timeout:
         }
         if (len > lv)
             len = lv;
-        if (len == 4) {
+        if (!optval_addr) {
+            /* writing to NULL does not give error */
+            len = 0;
+        } else if (len == 4) {
             if (put_user_u32(val, optval_addr))
                 return -TARGET_EFAULT;
         } else {
@@ -2877,18 +2884,24 @@ get_timeout:
                 return -TARGET_EINVAL;
             lv = sizeof(lv);
             ret = get_errno(getsockopt(sockfd, level, optname, &val, &lv));
+write_ret:
             if (ret < 0)
                 return ret;
-            if (len < sizeof(int) && len > 0 && val >= 0 && val < 255) {
+            if (!optval_addr) {
+                len = 0;
+            } else if (len < sizeof(int) && len > 0 && val >= 0 && val < 255) {
                 len = 1;
-                if (put_user_u32(len, optlen)
-                    || put_user_u8(val, optval_addr))
+                if (put_user_u8(val, optval_addr)) {
                     return -TARGET_EFAULT;
+                }
             } else {
                 if (len > sizeof(int))
                     len = sizeof(int);
-                if (put_user_u32(len, optlen)
-                    || put_user_u32(val, optval_addr))
+                if (put_user_u32(val, optval_addr)) {
+                    return -TARGET_EFAULT;
+                }
+            }
+            if (put_user_u32(len, optlen)) {
                     return -TARGET_EFAULT;
             }
             break;
@@ -2939,20 +2952,7 @@ get_timeout:
                 return -TARGET_EINVAL;
             lv = sizeof(lv);
             ret = get_errno(getsockopt(sockfd, level, optname, &val, &lv));
-            if (ret < 0)
-                return ret;
-            if (len < sizeof(int) && len > 0 && val >= 0 && val < 255) {
-                len = 1;
-                if (put_user_u32(len, optlen)
-                    || put_user_u8(val, optval_addr))
-                    return -TARGET_EFAULT;
-            } else {
-                if (len > sizeof(int))
-                    len = sizeof(int);
-                if (put_user_u32(len, optlen)
-                    || put_user_u32(val, optval_addr))
-                    return -TARGET_EFAULT;
-            }
+            goto write_ret;
             break;
         default:
             ret = -TARGET_ENOPROTOOPT;
@@ -2986,8 +2986,14 @@ get_timeout:
             if (ret < 0) {
                 return ret;
             }
-            if (put_user_u32(lv, optlen)
-                || put_user_u32(val, optval_addr)) {
+            if (optval_addr) {
+                if (put_user_u32(val, optval_addr)) {
+                    return -TARGET_EFAULT;
+                }
+            } else {
+                lv = 0;
+            }
+            if (put_user_u32(lv, optlen)) {
                 return -TARGET_EFAULT;
             }
             break;