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linux: Clear mode_t padding bits (BZ#25623)

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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.
This commit is contained in:
Adhemerval Zanella
2020-03-03 14:59:13 -03:00
parent d5e492ba4c
commit 24fdebe75f
3 changed files with 21 additions and 6 deletions
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9
sysdeps/unix/sysv/linux/shmctl.c
View File

@ -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;
}