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authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2020-03-03 14:59:13 -0300
committerAdhemerval Zanella <adhemerval.zanella@linaro.org>2020-03-05 14:40:28 -0300
commit24fdebe75f6df4c0edacb3f0cdc030913920aa4c (patch)
tree93fb399c11b914da400ce6f2a08c10b79e939eac /sysdeps/unix/sysv/linux/shmctl.c
parentd5e492ba4ced4a9101f82dbbd9de77223b9932ac (diff)
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linux: Clear mode_t padding bits (BZ#25623)
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 explicitly 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.
Diffstat (limited to 'sysdeps/unix/sysv/linux/shmctl.c')
-rw-r--r--sysdeps/unix/sysv/linux/shmctl.c9
1 files changed, 7 insertions, 2 deletions
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;
 }