From 05ba3f1aa1b04e921068249dd52a80bc84c2aeb4 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Mon, 30 Jul 2012 14:42:43 -0700 Subject: [PATCH] ipc: compat: use signed size_t types for msgsnd and msgrcv The msgsnd and msgrcv system calls use size_t to represent the size of the message being transferred. POSIX states that values of msgsz greater than SSIZE_MAX cause the result to be implementation-defined. On Linux, this equates to returning -EINVAL if (long) msgsz < 0. For compat tasks where !CONFIG_ARCH_WANT_OLD_COMPAT_IPC and compat_size_t is smaller than size_t, negative size values passed from userspace will be interpreted as positive values by do_msg{rcv,snd} and will fail to exit early with -EINVAL. This patch changes the compat prototypes for msg{rcv,snd} so that the message size is represented as a compat_ssize_t, which we cast to the native ssize_t type for the core IPC code. Cc: Arnd Bergmann Acked-by: Chris Metcalf Acked-by: Catalin Marinas Signed-off-by: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/compat.h | 4 ++-- ipc/compat.c | 8 ++++---- 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/include/linux/compat.h b/include/linux/compat.h index 9f68e90a14e..f2b8fe20cc8 100644 --- a/include/linux/compat.h +++ b/include/linux/compat.h @@ -266,9 +266,9 @@ long compat_sys_shmat(int first, int second, compat_uptr_t third, int version, #else long compat_sys_semctl(int semid, int semnum, int cmd, int arg); long compat_sys_msgsnd(int msqid, struct compat_msgbuf __user *msgp, - size_t msgsz, int msgflg); + compat_ssize_t msgsz, int msgflg); long compat_sys_msgrcv(int msqid, struct compat_msgbuf __user *msgp, - size_t msgsz, long msgtyp, int msgflg); + compat_ssize_t msgsz, long msgtyp, int msgflg); long compat_sys_shmat(int shmid, compat_uptr_t shmaddr, int shmflg); #endif long compat_sys_msgctl(int first, int second, void __user *uptr); diff --git a/ipc/compat.c b/ipc/compat.c index a41600f6ba5..20f92b2f293 100644 --- a/ipc/compat.c +++ b/ipc/compat.c @@ -373,21 +373,21 @@ long compat_sys_semctl(int semid, int semnum, int cmd, int arg) } long compat_sys_msgsnd(int msqid, struct compat_msgbuf __user *msgp, - size_t msgsz, int msgflg) + compat_ssize_t msgsz, int msgflg) { compat_long_t mtype; if (get_user(mtype, &msgp->mtype)) return -EFAULT; - return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg); + return do_msgsnd(msqid, mtype, msgp->mtext, (ssize_t)msgsz, msgflg); } long compat_sys_msgrcv(int msqid, struct compat_msgbuf __user *msgp, - size_t msgsz, long msgtyp, int msgflg) + compat_ssize_t msgsz, long msgtyp, int msgflg) { long err, mtype; - err = do_msgrcv(msqid, &mtype, msgp->mtext, msgsz, msgtyp, msgflg); + err = do_msgrcv(msqid, &mtype, msgp->mtext, (ssize_t)msgsz, msgtyp, msgflg); if (err < 0) goto out;