[Qemu-devel] [PATCH] 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>
---
 linux-user/syscall.c |   37 ++++++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index c2a2343..7bab006 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -2656,24 +2656,26 @@ static inline abi_long do_semctl(int semid, int semnum, 
int cmd,
             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);
+            err = host_to_target_semarray(semid, tswapal(target_su.array),
+                                          &array);
             if (err)
                 return 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);
+            err = host_to_target_semid_ds(tswapal(target_su.buf), &dsarg);
             if (err)
                 return err;
             break;
@@ -2681,7 +2683,7 @@ static inline abi_long do_semctl(int semid, int semnum, 
int cmd,
        case SEM_INFO:
             arg.__buf = &seminfo;
             ret = get_errno(semctl(semid, semnum, cmd, arg));
-            err = host_to_target_seminfo(target_su.__buf, &seminfo);
+            err = host_to_target_seminfo(tswapal(target_su.__buf), &seminfo);
             if (err)
                 return err;
             break;
@@ -3161,10 +3163,16 @@ static abi_long do_ipc(unsigned int call, int first,
         ret = get_errno(semget(first, second, third));
         break;
 
-    case IPCOP_semctl:
-        ret = do_semctl(first, second, third, (union target_semun)(abi_ulong) 
ptr);
+    case IPCOP_semctl: {
+        union target_semun *target_su;
+        if (!lock_user_struct(VERIFY_READ, target_su, ptr, 1)) {
+            ret = -TARGET_EFAULT;
+            break;
+        }
+        ret = do_semctl(first, second, third, *target_su);
+        unlock_user_struct(target_su, ptr, 0);
         break;
-
+    }
     case IPCOP_msgget:
         ret = get_errno(msgget(first, second));
         break;
@@ -3229,7 +3237,7 @@ 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);
@@ -6996,9 +7004,16 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
arg1,
         break;
 #endif
 #ifdef TARGET_NR_semctl
-    case TARGET_NR_semctl:
-        ret = do_semctl(arg1, arg2, arg3, (union target_semun)(abi_ulong)arg4);
+    case TARGET_NR_semctl: {
+        union target_semun *target_su;
+        if (!lock_user_struct(VERIFY_READ, target_su, arg4, 1)) {
+            ret = -TARGET_EFAULT;
+            break;
+        }
+        ret = do_semctl(arg1, arg2, arg3, *target_su);
+        unlock_user_struct(target_su, ptr, 0);
         break;
+    }
 #endif
 #ifdef TARGET_NR_msgctl
     case TARGET_NR_msgctl:
-- 
1.7.10.4