linux-kernel - [PATCH 2/4] x86/syscalls: Disallow compat entries for all types of 64-bit syscalls

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Message-Id: <4b7565954c5a06530ac01d98cb1592538fd8ae51.1562185330.git.luto@kernel.org>
Date:   Wed,  3 Jul 2019 13:34:03 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>
Subject: [PATCH 2/4] x86/syscalls: Disallow compat entries for all types of 64-bit syscalls

A "compat" entry in the syscall tables means to use a different
entry on 32-bit and 64-bit builds.  This only makes sense for
syscalls that exist in the first place in 32-bit builds, so disallow
it for anything other than i386.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/entry/syscalls/syscalltbl.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/syscalls/syscalltbl.sh b/arch/x86/entry/syscalls/syscalltbl.sh
index 94fcd1951aca..53c8c1a9adf9 100644
--- a/arch/x86/entry/syscalls/syscalltbl.sh
+++ b/arch/x86/entry/syscalls/syscalltbl.sh
@@ -27,8 +27,8 @@ emit() {
     compat="$4"
     umlentry=""
 
-    if [ "$abi" = "64" -a -n "$compat" ]; then
-	echo "a compat entry for a 64-bit syscall makes no sense" >&2
+    if [ "$abi" != "I386" -a -n "$compat" ]; then
+	echo "a compat entry ($abi: $compat) for a 64-bit syscall makes no sense" >&2
 	exit 1
     fi
 
-- 
2.21.0