ipc: set msg back to -EAGAIN if copy wasn't performed

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@parallels.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/ipc/msg.c b/ipc/msg.c
index 31cd1bf6af271771e67bdf6e29eb306371d3d130..fede1d06ef305cc59386bb4490c7e2e020b9f25d 100644 (file)
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -872,6 +872,7 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp,
                                                        goto out_unlock;
                                                break;
                                        }
+                                       msg = ERR_PTR(-EAGAIN);
                                } else
                                        break;
                                msg_counter++;