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Change the order of error checks in shmget so EEXIST is returned before 

EINVAL or EACCESS so callers have a more reliable way to tell if a
 shared memory segment already exists.
This commit is contained in:
erh 2008-10-27 15:40:56 +00:00
parent 05c3fa1435
commit 75072b1c6f
1 changed files with 11 additions and 6 deletions
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17
sys/kern/sysv_shm.c
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@ -1,4 +1,4 @@
/* $NetBSD: sysv_shm.c,v 1.112 2008/10/07 09:35:03 rmind Exp $ */
/* $NetBSD: sysv_shm.c,v 1.113 2008/10/27 15:40:56 erh Exp $ */
/*-
* Copyright (c) 1999, 2007 The NetBSD Foundation, Inc.
@ -61,7 +61,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: sysv_shm.c,v 1.112 2008/10/07 09:35:03 rmind Exp $");
__KERNEL_RCSID(0, "$NetBSD: sysv_shm.c,v 1.113 2008/10/27 15:40:56 erh Exp $");
#define SYSVSHM
@ -623,15 +623,20 @@ again:
goto again;
}
/* Check the permission, segment size and appropriate flag */
/*
* First check the flags, to generate a useful error when a
* segment already exists.
*/
if ((SCARG(uap, shmflg) & (IPC_CREAT | IPC_EXCL)) ==
(IPC_CREAT | IPC_EXCL))
return EEXIST;
/* Check the permission and segment size. */
error = ipcperm(cred, &shmseg->shm_perm, mode);
if (error)
return error;
if (SCARG(uap, size) && SCARG(uap, size) > shmseg->shm_segsz)
return EINVAL;
if ((SCARG(uap, shmflg) & (IPC_CREAT | IPC_EXCL)) ==
(IPC_CREAT | IPC_EXCL))
return EEXIST;
*retval = IXSEQ_TO_IPCID(segnum, shmseg->shm_perm);
return 0;