Hi Peter,
You wrote:
When MSG_COPY is set, a duplicate message must be allocated for
the copy before locking the queue. However, the copy could
not be larger than was sent which is limited to msg_ctlmax.
Signed-off-by: Peter Hurley <pe...@hurleysoftware.com>
---
ipc/msg.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/ipc/msg.c b/ipc/msg.c
index 950572f..31cd1bf 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -820,15 +820,17 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz,
long msgtyp,
struct msg_msg *copy = NULL;
unsigned long copy_number = 0;
+ ns = current->nsproxy->ipc_ns;
+
if (msqid < 0 || (long) bufsz < 0)
return -EINVAL;
if (msgflg & MSG_COPY) {
- copy = prepare_copy(buf, bufsz, msgflg, &msgtyp, ©_number);
+ copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax),
+ msgflg, &msgtyp, ©_number);
What about:
- increase msg_ctlmax
- send message
- reduce msg_ctlmax
The side effects of the patch are odd:
- without MSG_COPY, a message can be read regardsless of the size.
The user could check for E2BIG and increase the buffer size until
msgrcv succeeds.
- with MSG_COPY, something else would happen.
As far as I can see, it would oops: msg_ctlmax bytes are allocated,
then the E2BIG test is against bufsz, and copy_msg() doesn't check
the size of the target buffer.
I.e.: I would propose to revert the patch.
--
Manfred
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