From: Svenning Sørensen <sss@xxxxxxxxxx>
Subject: 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 daaf74cf0867e3042090d56d10b194d6265b4684
Author: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
AuthorDate: Tue Apr 30 19:15:04 2013 -0700
Commit: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
CommitDate: Wed May 1 08:12:57 2013 -0700
ipc: refactor msg list search into separate function
Signed-off-by: Svenning Soerensen <sss@xxxxxxxxxx>
Reviewed-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
ipc/msg.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff -puN ipc/msg.c~ipc-bugfix-for-msgrcv-with-msgtyp-0 ipc/msg.c
--- a/ipc/msg.c~ipc-bugfix-for-msgrcv-with-msgtyp-0
+++ a/ipc/msg.c
@@ -839,7 +839,7 @@ static inline void free_copy(struct msg_
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 m
*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 m
}
}
- return ERR_PTR(-EAGAIN);
+ return found ?: ERR_PTR(-EAGAIN);
}
long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg,
_
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