On Tue, Sep 06, 2016 at 01:56:40PM -0400, Kees Cook wrote:
SNIP
> > static __must_check __always_inline int
> > diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
> > index a939f5ed7f89..c7a22a8a157e 100644
> > --- a/fs/proc/kcore.c
> > +++ b/fs/proc/kcore.c
> > @@ -516,7 +516,7 @@ read_kcore(struct file *file, char __user *buffer,
> > size_t buflen, loff_t *fpos)
> > if (kern_addr_valid(start)) {
> > unsigned long n;
> >
> > - n = copy_to_user(buffer, (char *)start,
> > tsz);
> > + n = copy_to_user_nocheck(buffer, (char
> > *)start, tsz);
> > /*
> > * We cannot distinguish between fault on
> > source
> > * and fault on destination. When this
> > happens
>
> This patch is x86-specific (but ARCH_PROC_KCORE_TEXT is on multiple
> architectures), which I don't think we want. Instead, let's get the
> usercopy helper code centralized (Al Viro is looking at this already),
> and then we can design arch-agnostic methods to handle this.
>
> In the meantime, how about continuing to use a bounce buffer like
> already done in the vmalloc_or_module_addr() case immediately above?
ok, sounds good.. so something like below? untested
thanks,
jirka
---
diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index a939f5ed7f89..de07c273f725 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -515,8 +515,20 @@ read_kcore(struct file *file, char __user *buffer, size_t
buflen, loff_t *fpos)
} else {
if (kern_addr_valid(start)) {
unsigned long n;
+ char *buf;
- n = copy_to_user(buffer, (char *)start, tsz);
+ buf = kzalloc(tsz, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ /*
+ * Using bounce buffer to bypass the hardened
+ * user copy kernel text checks.
+ */
+ memcpy(buf, (char *) start, tsz);
+
+ n = copy_to_user(buffer, buf, tsz);
+ kfree(buf);
/*
* We cannot distinguish between fault on source
* and fault on destination. When this happens
