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Subject[PATCH] x86: Fix x32 System V message queue syscalls
POSIX specifies that the first field of the supplied msgp, namely mtype,
is a long, not a __kernel_long_t, and it's a user-defined struct due to
the variable-length mtext field so we can't even bend the spec and make
it a __kernel_long_t even if we wanted to. Thus we must use the compat
syscalls on x32 to avoid buffer overreads and overflows in msgsnd and
msgrcv respectively.

Due to erroneously including the first 4 bytes of mtext in the mtype
this would previously also cause non-zero msgtyp arguments for msgrcv to
search for the wrong messages, and if sharing message queues between x32
and non-x32 (i386 or x86_64) processes this would previously cause mtext
to "move" and, depending on the direction and ABI combination, lose the
first 4 bytes.

Signed-off-by: Jessica Clarke <>
arch/x86/entry/syscalls/syscall_64.tbl | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index f30d6ae9a..7ee40989e 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -77,8 +77,8 @@
66 common semctl sys_semctl
67 common shmdt sys_shmdt
68 common msgget sys_msgget
-69 common msgsnd sys_msgsnd
-70 common msgrcv sys_msgrcv
+69 64 msgsnd sys_msgsnd
+70 64 msgrcv sys_msgrcv
71 common msgctl sys_msgctl
72 common fcntl sys_fcntl
73 common flock sys_flock
@@ -404,3 +404,5 @@
545 x32 execveat compat_sys_execveat
546 x32 preadv2 compat_sys_preadv64v2
547 x32 pwritev2 compat_sys_pwritev64v2
+548 x32 msgsnd compat_sys_msgsnd
+549 x32 msgrcv compat_sys_msgrcv
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