From: Kees Cook <keescook@chromium.org>
To: Russell King <linux@armlinux.org.uk>
Cc: Kees Cook <keescook@chromium.org>,
Mark Brown <broonie@kernel.org>, Ard Biesheuvel <ardb@kernel.org>,
Wang Kefeng <wangkefeng.wang@huawei.com>,
Andrew Morton <akpm@linux-foundation.org>,
Ben Hutchings <ben@decadent.org.uk>,
linux-arm-kernel@lists.infradead.org,
"Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>,
Hugh Dickins <hughd@google.com>,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: [PATCH] ARM: fault: Implement copy_from_kernel_nofault_allowed()
Date: Mon, 22 Jan 2024 17:12:38 -0800 [thread overview]
Message-ID: <20240123011238.work.301-kees@kernel.org> (raw)
Under PAN emulation when dumping backtraces from things like the
LKDTM EXEC_USERSPACE test[1], a double fault (which would hang a CPU)
would happen because of dump_instr() attempting to read a userspace
address. Make sure copy_from_kernel_nofault() does not attempt this
any more.
Reported-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/all/202401181125.D48DCB4C@keescook/ [1]
Suggested-by: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Wang Kefeng <wangkefeng.wang@huawei.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/arm/mm/fault.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index e804432e905e..bc5b959b6f90 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -25,6 +25,13 @@
#include "fault.h"
+bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size)
+{
+ unsigned long addr = (unsigned long)unsafe_src;
+
+ return addr >= TASK_SIZE && ULONG_MAX - addr >= size;
+}
+
#ifdef CONFIG_MMU
/*
--
2.34.1
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next reply other threads:[~2024-01-23 1:13 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-23 1:12 Kees Cook [this message]
2024-01-23 13:44 ` [PATCH] ARM: fault: Implement copy_from_kernel_nofault_allowed() Ard Biesheuvel
2024-01-23 19:02 ` Mark Brown
2024-02-21 6:39 ` Kees Cook
2024-02-21 11:29 ` Russell King (Oracle)
2024-02-21 11:31 ` Russell King (Oracle)
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