From: James Hogan <jhogan@kernel.org>
Date: Tue, 20 Feb 2018 15:44:37 +0000 (+0000)
Subject: MIPS: Drop spurious __unused in struct compat_flock
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=6ae1756faddefd7494353380ee546dd38c2f97eb;p=openwrt%2Fstaging%2Fblogic.git

MIPS: Drop spurious __unused in struct compat_flock

MIPS' struct compat_flock doesn't match the 32-bit struct flock, as it
has an extra short __unused before pad[4], which combined with alignment
increases the size to 40 bytes compared with struct flock's 36 bytes.

Since commit 8c6657cb50cb ("Switch flock copyin/copyout primitives to
copy_{from,to}_user()"), put_compat_flock() writes the full compat_flock
struct to userland, which results in corruption of the userland word
after the struct flock when running 32-bit userlands on 64-bit kernels.

This was observed to cause a bus error exception when starting Firefox
on Debian 8 (Jessie).

Reported-by: Peter Mamonov <pmamonov@gmail.com>
Signed-off-by: James Hogan <jhogan@kernel.org>
Tested-by: Peter Mamonov <pmamonov@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-mips@linux-mips.org
Cc: <stable@vger.kernel.org> # 4.13+
Patchwork: https://patchwork.linux-mips.org/patch/18646/
---

diff --git a/arch/mips/include/asm/compat.h b/arch/mips/include/asm/compat.h
index 946681db8dc3..9a0fa66b81ac 100644
--- a/arch/mips/include/asm/compat.h
+++ b/arch/mips/include/asm/compat.h
@@ -86,7 +86,6 @@ struct compat_flock {
 	compat_off_t	l_len;
 	s32		l_sysid;
 	compat_pid_t	l_pid;
-	short		__unused;
 	s32		pad[4];
 };