This is a note to let you know that I've just added the patch titled
lib/syscall: fix syscall registers retrieval on 32-bit platforms
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
lib-syscall-fix-syscall-registers-retrieval-on-32-bit-platforms.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4f134b89a24b965991e7c345b9a4591821f7c2a6 Mon Sep 17 00:00:00 2001
From: Willy Tarreau <w@xxxxxx>
Date: Mon, 30 Nov 2020 08:36:48 +0100
Subject: lib/syscall: fix syscall registers retrieval on 32-bit platforms
From: Willy Tarreau <w@xxxxxx>
commit 4f134b89a24b965991e7c345b9a4591821f7c2a6 upstream.
Lilith >_> and Claudio Bozzato of Cisco Talos security team reported
that collect_syscall() improperly casts the syscall registers to 64-bit
values leaking the uninitialized last 24 bytes on 32-bit platforms, that
are visible in /proc/self/syscall.
The cause is that info->data.args are u64 while syscall_get_arguments()
uses longs, as hinted by the bogus pointer cast in the function.
Let's just proceed like the other call places, by retrieving the
registers into an array of longs before assigning them to the caller's
array. This was successfully tested on x86_64, i386 and ppc32.
Reference: CVE-2020-28588, TALOS-2020-1211
Fixes: 631b7abacd02 ("ptrace: Remove maxargs from task_current_syscall()")
Cc: Greg KH <greg@xxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Tested-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> (ppc32)
Signed-off-by: Willy Tarreau <w@xxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
lib/syscall.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
--- a/lib/syscall.c
+++ b/lib/syscall.c
@@ -7,6 +7,7 @@
static int collect_syscall(struct task_struct *target, struct syscall_info *info)
{
+ unsigned long args[6] = { };
struct pt_regs *regs;
if (!try_get_task_stack(target)) {
@@ -27,8 +28,14 @@ static int collect_syscall(struct task_s
info->data.nr = syscall_get_nr(target, regs);
if (info->data.nr != -1L)
- syscall_get_arguments(target, regs,
- (unsigned long *)&info->data.args[0]);
+ syscall_get_arguments(target, regs, args);
+
+ info->data.args[0] = args[0];
+ info->data.args[1] = args[1];
+ info->data.args[2] = args[2];
+ info->data.args[3] = args[3];
+ info->data.args[4] = args[4];
+ info->data.args[5] = args[5];
put_task_stack(target);
return 0;
Patches currently in stable-queue which might be from w@xxxxxx are
queue-5.4/lib-syscall-fix-syscall-registers-retrieval-on-32-bit-platforms.patch
