From: Will Deacon <will.dea...@arm.com>
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.
Signed-off-by: Will Deacon <will.dea...@arm.com>
Signed-off-by: Catalin Marinas <catalin.mari...@arm.com>
---
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 9f68e90..f2b8fe2 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 a41600f..20f92b2 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;
--
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