From 24fdebe75f6df4c0edacb3f0cdc030913920aa4c Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Tue, 3 Mar 2020 14:59:13 -0300 Subject: 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. --- sysdeps/unix/sysv/linux/shmctl.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'sysdeps/unix/sysv/linux/shmctl.c') 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; } -- cgit 1.4.1