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Message-Id: <1515531365-37423-28-git-send-email-keescook@chromium.org>
Date: Tue, 9 Jan 2018 12:55:56 -0800
From: Kees Cook <keescook@...omium.org>
To: linux-kernel@...r.kernel.org
Cc: Kees Cook <keescook@...omium.org>,
David Windsor <dave@...lcore.net>,
Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Andy Lutomirski <luto@...nel.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Christoph Hellwig <hch@...radead.org>,
Christoph Lameter <cl@...ux.com>,
"David S. Miller" <davem@...emloft.net>,
Laura Abbott <labbott@...hat.com>,
Mark Rutland <mark.rutland@....com>,
"Martin K. Petersen" <martin.petersen@...cle.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Christian Borntraeger <borntraeger@...ibm.com>,
Christoffer Dall <christoffer.dall@...aro.org>,
Dave Kleikamp <dave.kleikamp@...cle.com>,
Jan Kara <jack@...e.cz>,
Luis de Bethencourt <luisbg@...nel.org>,
Marc Zyngier <marc.zyngier@....com>,
Rik van Riel <riel@...hat.com>,
Matthew Garrett <mjg59@...gle.com>,
linux-fsdevel@...r.kernel.org,
linux-arch@...r.kernel.org,
netdev@...r.kernel.org,
linux-mm@...ck.org,
kernel-hardening@...ts.openwall.com
Subject: [PATCH 27/36] fork: Define usercopy region in thread_stack slab caches
From: David Windsor <dave@...lcore.net>
In support of usercopy hardening, this patch defines a region in the
thread_stack slab caches in which userspace copy operations are allowed.
Since the entire thread_stack needs to be available to userspace, the
entire slab contents are whitelisted. Note that the slab-based thread
stack is only present on systems with THREAD_SIZE < PAGE_SIZE and
!CONFIG_VMAP_STACK.
cache object allocation:
kernel/fork.c:
alloc_thread_stack_node(...):
return kmem_cache_alloc_node(thread_stack_cache, ...)
dup_task_struct(...):
...
stack = alloc_thread_stack_node(...)
...
tsk->stack = stack;
copy_process(...):
...
dup_task_struct(...)
_do_fork(...):
...
copy_process(...)
This region is known as the slab cache's usercopy region. Slab caches
can now check that each dynamically sized copy operation involving
cache-managed memory falls entirely within the slab's usercopy region.
This patch is modified from Brad Spengler/PaX Team's PAX_USERCOPY
whitelisting code in the last public patch of grsecurity/PaX based on my
understanding of the code. Changes or omissions from the original code are
mine and don't reflect the original grsecurity/PaX code.
Signed-off-by: David Windsor <dave@...lcore.net>
[kees: adjust commit log, split patch, provide usage trace]
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Andy Lutomirski <luto@...nel.org>
Signed-off-by: Kees Cook <keescook@...omium.org>
Acked-by: Rik van Riel <riel@...hat.com>
---
kernel/fork.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/fork.c b/kernel/fork.c
index 82f2a0441d3b..0e086af148f2 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -282,8 +282,9 @@ static void free_thread_stack(struct task_struct *tsk)
void thread_stack_cache_init(void)
{
- thread_stack_cache = kmem_cache_create("thread_stack", THREAD_SIZE,
- THREAD_SIZE, 0, NULL);
+ thread_stack_cache = kmem_cache_create_usercopy("thread_stack",
+ THREAD_SIZE, THREAD_SIZE, 0, 0,
+ THREAD_SIZE, NULL);
BUG_ON(thread_stack_cache == NULL);
}
# endif
--
2.7.4
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