[v2,2/2] linux: Clear mode_t padding bits (BZ#25623)
Commit Message
Changes from previous version:
- Fixed sizeof check and use __kernel_mode_t.
--
The kernel might not clear the padding value for the ipc_perm mode
fields in compat mode (32 bit running on a 64 bit kernel). It was
fixed on v4.14 when the ipc compat code was refactored to move
(commits 553f770ef71b, 469391684626, c0ebccb6fa1e).
Although it is most likely a kernel issue, it was shown only due
BZ#18231 fix which made all the SysVIPC mode_t 32-bit regardless of
the kABI.
This patch fixes it by explicit zeroing the upper bits for such
cases. The __ASSUME_SYSVIPC_BROKEN_MODE_T case already handles
it with the shift.
(The aarch64 ipc_priv.h is superflous since
__ASSUME_SYSVIPC_DEFAULT_IPC_64 is now defined as default).
Checked on i686-linux-gnu on 3.10 and on 4.15 kernel.
---
sysdeps/unix/sysv/linux/msgctl.c | 9 +++++++--
sysdeps/unix/sysv/linux/semctl.c | 9 +++++++--
sysdeps/unix/sysv/linux/shmctl.c | 9 +++++++--
3 files changed, 21 insertions(+), 6 deletions(-)
Comments
On Mär 04 2020, Adhemerval Zanella wrote:
> The kernel might not clear the padding value for the ipc_perm mode
> fields in compat mode (32 bit running on a 64 bit kernel). It was
> fixed on v4.14 when the ipc compat code was refactored to move
> (commits 553f770ef71b, 469391684626, c0ebccb6fa1e).
>
> Although it is most likely a kernel issue, it was shown only due
> BZ#18231 fix which made all the SysVIPC mode_t 32-bit regardless of
> the kABI.
>
> This patch fixes it by explicit zeroing the upper bits for such
s/explicit/explicitly/
> cases. The __ASSUME_SYSVIPC_BROKEN_MODE_T case already handles
> it with the shift.
>
> (The aarch64 ipc_priv.h is superflous since
> __ASSUME_SYSVIPC_DEFAULT_IPC_64 is now defined as default).
>
> Checked on i686-linux-gnu on 3.10 and on 4.15 kernel.
Ok.
Andreas.
@@ -61,7 +61,6 @@ __new_msgctl (int msqid, int cmd, struct msqid_ds *buf)
int ret = msgctl_syscall (msqid, cmd, buf);
-#ifdef __ASSUME_SYSVIPC_BROKEN_MODE_T
if (ret >= 0)
{
switch (cmd)
@@ -69,10 +68,16 @@ __new_msgctl (int msqid, int cmd, struct msqid_ds *buf)
case IPC_STAT:
case MSG_STAT:
case MSG_STAT_ANY:
+#ifdef __ASSUME_SYSVIPC_BROKEN_MODE_T
buf->msg_perm.mode >>= 16;
+#else
+ /* Old Linux kernel versions might not clear the mode padding. */
+ if (sizeof ((struct msqid_ds){0}.msg_perm.mode)
+ != sizeof (__kernel_mode_t))
+ buf->msg_perm.mode &= 0xFFFF;
+#endif
}
}
-#endif
return ret;
}
@@ -92,7 +92,6 @@ __new_semctl (int semid, int semnum, int cmd, ...)
int ret = semctl_syscall (semid, semnum, cmd, arg);
-#ifdef __ASSUME_SYSVIPC_BROKEN_MODE_T
if (ret >= 0)
{
switch (cmd)
@@ -100,10 +99,16 @@ __new_semctl (int semid, int semnum, int cmd, ...)
case IPC_STAT:
case SEM_STAT:
case SEM_STAT_ANY:
+#ifdef __ASSUME_SYSVIPC_BROKEN_MODE_T
arg.buf->sem_perm.mode >>= 16;
+#else
+ /* Old Linux kernel versions might not clear the mode padding. */
+ if (sizeof ((struct semid_ds){0}.sem_perm.mode)
+ != sizeof (__kernel_mode_t))
+ arg.buf->sem_perm.mode &= 0xFFFF;
+#endif
}
}
-#endif
return ret;
}
@@ -63,7 +63,6 @@ __new_shmctl (int shmid, int cmd, struct shmid_ds *buf)
int ret = shmctl_syscall (shmid, cmd, buf);
-#ifdef __ASSUME_SYSVIPC_BROKEN_MODE_T
if (ret >= 0)
{
switch (cmd)
@@ -71,10 +70,16 @@ __new_shmctl (int shmid, int cmd, struct shmid_ds *buf)
case IPC_STAT:
case SHM_STAT:
case SHM_STAT_ANY:
+#ifdef __ASSUME_SYSVIPC_BROKEN_MODE_T
buf->shm_perm.mode >>= 16;
+#else
+ /* Old Linux kernel versions might not clear the mode padding. */
+ if (sizeof ((struct shmid_ds){0}.shm_perm.mode)
+ != sizeof (__kernel_mode_t))
+ buf->shm_perm.mode &= 0xFFFF;
+#endif
}
}
-#endif
return ret;
}