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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 daaf74cf08 ("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>
This commit is contained in:
Svenning Sørensen 2013-08-28 16:35:17 -07:00 committed by Linus Torvalds
parent aaaafb7f95
commit 368ae537e0
1 changed files with 3 additions and 2 deletions
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5
ipc/msg.c
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@ -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,