Fwd: [PATCH] ipc: fix compat msgrcv with negative msgtyp

[Masanari Iida]

Greg,
Somebody asking to backport following patch into 3.10.x stable tree.
https://lkml.org/lkml/2015/3/7/316

The patch is identified as following commit ID in Linus's tree.

commit e7ca2552369c1dfe0216c626baf82c3d83ec36bb
Author: Mateusz Guzik <mguzik@xxxxxxxxxx>
Date:   Mon Jan 27 17:07:11 2014 -0800

    ipc: fix compat msgrcv with negative msgtyp

For your convinience, the patch is included in this e-mail.

Masanari Iida

---------- Forwarded message ----------
From: Mateusz Guzik <mguzik@xxxxxxxxxx>
Date: Wed, Jan 15, 2014 at 10:52 PM
Subject: [PATCH] ipc: fix compat msgrcv with negative msgtyp
To: linux-kernel@xxxxxxxxxxxxxxx
Cc: Gabriellla Schmidt <gsc@xxxxxxxxx>, Al Viro <viro@xxxxxxxxxxxxxxxxxx>


Compat function takes msgtyp argument as u32 and passes it down to
do_msgrcv which results in casting to long, thus the sign is lost
and we get a big positive number instead.

Cast the argument to signed type before passing it down.

Signed-off-by: Mateusz Guzik <mguzik@xxxxxxxxxx>
Reported-by: Gabriellla Schmidt <gsc@xxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
 ipc/compat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ipc/compat.c b/ipc/compat.c
index 892f658..d3b3760 100644
--- a/ipc/compat.c
+++ b/ipc/compat.c
@@ -381,7 +381,7 @@ COMPAT_SYSCALL_DEFINE6(ipc, u32, call, int, first,
int, second,
                        uptr = compat_ptr(ipck.msgp);
                        fifth = ipck.msgtyp;
                }
-               return do_msgrcv(first, uptr, second, fifth, third,
+               return do_msgrcv(first, uptr, second, (s32)fifth, third,
                                 compat_do_msg_fill);
        }
        case MSGGET:
--
1.8.3.1

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