Commit 368ae537 authored Aug 28, 2013 by Svenning Sørensen Committed by Linus Torvalds Aug 28, 2013

IPC: bugfix for msgrcv with msgtyp < 0



According to 'man msgrcv': "If msgtyp is less than 0, the first message of
the lowest type that is less than or equal to the absolute value of msgtyp
shall be received."

Bug: The kernel only returns a message if its type is 1; other messages
with type < abs(msgtype) will never get returned.

Fix: After having traversed the list to find the first message with the
lowest type, we need to actually return that message.

This regression was introduced by commit daaf74cf ("ipc: refactor
msg list search into separate function")

Signed-off-by: Svenning Soerensen <sss@secomea.dk>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent aaaafb7f

ipc/msg.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -839,7 +839,7 @@ static inline void free_copy(struct msg_msg *copy)

		static struct msg_msg find_msg(struct msg_queue msq, long *msgtyp, int mode)
		{
		struct msg_msg *msg;
		struct msg_msg msg, found = NULL;
		long count = 0;

		list_for_each_entry(msg, &msq->q_messages, m_list) {
		@@ -848,6 +848,7 @@ static struct msg_msg find_msg(struct msg_queue msq, long *msgtyp, int mode)
		*msgtyp, mode)) {
		if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) {
		*msgtyp = msg->m_type - 1;
		found = msg;
		} else if (mode == SEARCH_NUMBER) {
		if (*msgtyp == count)
		return msg;
		@@ -857,7 +858,7 @@ static struct msg_msg find_msg(struct msg_queue msq, long *msgtyp, int mode)
		}
		}

		return ERR_PTR(-EAGAIN);
		return found ?: ERR_PTR(-EAGAIN);
		}

		long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg,