[v2,2/2] linux: Clear mode_t padding bits (BZ#25623)

Message ID 20200304124723.1334-2-adhemerval.zanella@linaro.org
State Accepted
Commit 24fdebe75f6df4c0edacb3f0cdc030913920aa4c
Headers show
Series
  • [v2,1/2] linux: Remove aarch64 ipc_priv.h
Related show

Commit Message

Adhemerval Zanella March 4, 2020, 12:47 p.m.
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(-)

-- 
2.17.1

Comments

Andreas Schwab March 5, 2020, 5:06 p.m. | #1
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.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

Patch

diff --git a/sysdeps/unix/sysv/linux/msgctl.c b/sysdeps/unix/sysv/linux/msgctl.c
index 27879e76cd..eb28835b3a 100644
--- a/sysdeps/unix/sysv/linux/msgctl.c
+++ b/sysdeps/unix/sysv/linux/msgctl.c
@@ -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;
 }
diff --git a/sysdeps/unix/sysv/linux/semctl.c b/sysdeps/unix/sysv/linux/semctl.c
index 0c3eb0932f..0a79e8e4f5 100644
--- a/sysdeps/unix/sysv/linux/semctl.c
+++ b/sysdeps/unix/sysv/linux/semctl.c
@@ -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;
 }
diff --git a/sysdeps/unix/sysv/linux/shmctl.c b/sysdeps/unix/sysv/linux/shmctl.c
index 39fa861e17..aed9e5260e 100644
--- a/sysdeps/unix/sysv/linux/shmctl.c
+++ b/sysdeps/unix/sysv/linux/shmctl.c
@@ -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;
 }