[Qemu-devel] [PATCH][v4] linux-user: correct semctl() and shmctl()

[Laurent Vivier]

The parameter "union semun" of semctl() is not a value
but a pointer to the value.

Moreover, all fields of target_su must be swapped (if needed).

The third argument of shmctl is a pointer.

WITHOUT this patch:

$ ipcs

kernel not configured for shared memory

qemu: uncaught target signal 11 (Segmentation fault) - core dumped

WITH this patch:

$ ipcs

------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status
0x4e545030 0          root      600        96         1
0x4e545031 32769      root      600        96         1
0x4e545032 65538      root      666        96         1
0x4e545033 98307      root      666        96         1
0x47505344 131076     root      666        8240       1
0x3c81b7f5 163845     laurent   666        4096       0
0x00000000 729513990  laurent   600        393216     2          dest
0x00000000 729546759  laurent   600        393216     2          dest
0x00000000 1879179273 laurent   600        393216     2          dest

------ Semaphore Arrays --------
key        semid      owner      perms      nsems
0x3c81b7f6 32768      laurent   666        1
0x1c44ac47 6586369    laurent   600        1

------ Message Queues --------
key        msqid      owner      perms      used-bytes   messages
0x1c44ac45 458752     laurent    600        0            0
0x1c44ac46 491521     laurent    600        0            0

Signed-off-by: Laurent Vivier <address@hidden>
---
v2: move lock_user_struct() in do_semctl()
v3: correctly set the return value
v3: don't duplicat unlock_user_struct(), set err to ret instead

 linux-user/syscall.c |   44 +++++++++++++++++++++++++++-----------------
 1 file changed, 27 insertions(+), 17 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 08538fc..1aef535 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -2652,8 +2652,9 @@ static inline abi_long host_to_target_semarray(int semid, 
abi_ulong target_addr,
 }
 
 static inline abi_long do_semctl(int semid, int semnum, int cmd,
-                                 union target_semun target_su)
+                                 abi_ulong ptr)
 {
+    union target_semun *target_su;
     union semun arg;
     struct semid_ds dsarg;
     unsigned short *array = NULL;
@@ -2662,43 +2663,51 @@ static inline abi_long do_semctl(int semid, int semnum, 
int cmd,
     abi_long err;
     cmd &= 0xff;
 
+    if (!lock_user_struct(VERIFY_READ, target_su, ptr, 1)) {
+        return -TARGET_EFAULT;
+    }
     switch( cmd ) {
        case GETVAL:
        case SETVAL:
-            arg.val = tswap32(target_su.val);
+            arg.val = tswap32(target_su->val);
             ret = get_errno(semctl(semid, semnum, cmd, arg));
-            target_su.val = tswap32(arg.val);
+            target_su->val = tswap32(arg.val);
             break;
        case GETALL:
        case SETALL:
-            err = target_to_host_semarray(semid, &array, target_su.array);
+            err = target_to_host_semarray(semid, &array,
+                                          tswapal(target_su->array));
             if (err)
                 return err;
             arg.array = array;
             ret = get_errno(semctl(semid, semnum, cmd, arg));
-            err = host_to_target_semarray(semid, target_su.array, &array);
-            if (err)
-                return err;
+            err = host_to_target_semarray(semid, tswapal(target_su->array),
+                                          &array);
+            if (err) {
+                ret = err;
+            }
             break;
        case IPC_STAT:
        case IPC_SET:
        case SEM_STAT:
-            err = target_to_host_semid_ds(&dsarg, target_su.buf);
+            err = target_to_host_semid_ds(&dsarg, tswapal(target_su->buf));
             if (err)
                 return err;
             arg.buf = &dsarg;
             ret = get_errno(semctl(semid, semnum, cmd, arg));
-            err = host_to_target_semid_ds(target_su.buf, &dsarg);
-            if (err)
-                return err;
+            err = host_to_target_semid_ds(tswapal(target_su->buf), &dsarg);
+            if (err) {
+                ret = err;
+            }
             break;
        case IPC_INFO:
        case SEM_INFO:
             arg.__buf = &seminfo;
             ret = get_errno(semctl(semid, semnum, cmd, arg));
-            err = host_to_target_seminfo(target_su.__buf, &seminfo);
-            if (err)
-                return err;
+            err = host_to_target_seminfo(tswapal(target_su->__buf), &seminfo);
+            if (err) {
+                ret = err;
+            }
             break;
        case IPC_RMID:
        case GETPID:
@@ -2707,6 +2716,7 @@ static inline abi_long do_semctl(int semid, int semnum, 
int cmd,
             ret = get_errno(semctl(semid, semnum, cmd, NULL));
             break;
     }
+    unlock_user_struct(target_su, ptr, 0);
 
     return ret;
 }
@@ -3177,7 +3187,7 @@ static abi_long do_ipc(unsigned int call, int first,
         break;
 
     case IPCOP_semctl:
-        ret = do_semctl(first, second, third, (union target_semun)(abi_ulong) 
ptr);
+        ret = do_semctl(first, second, third, ptr);
         break;
 
     case IPCOP_msgget:
@@ -3244,7 +3254,7 @@ static abi_long do_ipc(unsigned int call, int first,
 
        /* IPC_* and SHM_* command values are the same on all linux platforms */
     case IPCOP_shmctl:
-        ret = do_shmctl(first, second, third);
+        ret = do_shmctl(first, second, ptr);
         break;
     default:
        gemu_log("Unsupported ipc call: %d (version %d)\n", call, version);
@@ -6933,7 +6943,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
 #endif
 #ifdef TARGET_NR_semctl
     case TARGET_NR_semctl:
-        ret = do_semctl(arg1, arg2, arg3, (union target_semun)(abi_ulong)arg4);
+        ret = do_semctl(arg1, arg2, arg3, arg4);
         break;
 #endif
 #ifdef TARGET_NR_msgctl
-- 
1.7.10.4