[ 11/27] ipc: set msg back to -EAGAIN if copy wasnt performed

[Greg Kroah-Hartman]

3.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stanislav Kinsbursky <skinsbursky@xxxxxxxxxxxxx>

commit 2dc958fa2fe6987e7ab106bd97029a09a82fcd8d upstream.

Make sure that msg pointer is set back to error value in case of
MSG_COPY flag is set and desired message to copy wasn't found.  This
garantees that msg is either a error pointer or a copy address.

Otherwise the last message in queue will be freed without unlinking from
the queue (which leads to memory corruption) and the dummy allocated
copy won't be released.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@xxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 ipc/msg.c |    1 +
 1 file changed, 1 insertion(+)

--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -872,6 +872,7 @@ long do_msgrcv(int msqid, void __user *b
 							goto out_unlock;
 						break;
 					}
+					msg = ERR_PTR(-EAGAIN);
 				} else
 					break;
 				msg_counter++;


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