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authorKees Cook <keescook@chromium.org>2022-02-16 23:05:28 +0300
committerKees Cook <keescook@chromium.org>2022-02-26 05:20:11 +0300
commit2792d84e6da5e0fd7d3b22fd70bc69b7ee263609 (patch)
tree44aab0a09e06fc25131dbac9b427cc5cce71e244 /arch/sh
parentefa90c11f62e6b7252fb75efe2787056872a627c (diff)
downloadlinux-2792d84e6da5e0fd7d3b22fd70bc69b7ee263609.tar.xz
usercopy: Check valid lifetime via stack depth
One of the things that CONFIG_HARDENED_USERCOPY sanity-checks is whether an object that is about to be copied to/from userspace is overlapping the stack at all. If it is, it performs a number of inexpensive bounds checks. One of the finer-grained checks is whether an object crosses stack frames within the stack region. Doing this on x86 with CONFIG_FRAME_POINTER was cheap/easy. Doing it with ORC was deemed too heavy, and was left out (a while ago), leaving the courser whole-stack check. The LKDTM tests USERCOPY_STACK_FRAME_TO and USERCOPY_STACK_FRAME_FROM try to exercise these cross-frame cases to validate the defense is working. They have been failing ever since ORC was added (which was expected). While Muhammad was investigating various LKDTM failures[1], he asked me for additional details on them, and I realized that when exact stack frame boundary checking is not available (i.e. everything except x86 with FRAME_POINTER), it could check if a stack object is at least "current depth valid", in the sense that any object within the stack region but not between start-of-stack and current_stack_pointer should be considered unavailable (i.e. its lifetime is from a call no longer present on the stack). Introduce ARCH_HAS_CURRENT_STACK_POINTER to track which architectures have actually implemented the common global register alias. Additionally report usercopy bounds checking failures with an offset from current_stack_pointer, which may assist with diagnosing failures. The LKDTM USERCOPY_STACK_FRAME_TO and USERCOPY_STACK_FRAME_FROM tests (once slightly adjusted in a separate patch) pass again with this fixed. [1] https://github.com/kernelci/kernelci-project/issues/84 Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: linux-mm@kvack.org Reported-by: Muhammad Usama Anjum <usama.anjum@collabora.com> Signed-off-by: Kees Cook <keescook@chromium.org> --- v1: https://lore.kernel.org/lkml/20220216201449.2087956-1-keescook@chromium.org v2: https://lore.kernel.org/lkml/20220224060342.1855457-1-keescook@chromium.org v3: https://lore.kernel.org/lkml/20220225173345.3358109-1-keescook@chromium.org v4: - improve commit log (akpm)
Diffstat (limited to 'arch/sh')
-rw-r--r--arch/sh/Kconfig1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 2474a04ceac4..1c2b53bf3093 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -7,6 +7,7 @@ config SUPERH
select ARCH_HAVE_CUSTOM_GPIO_H
select ARCH_HAVE_NMI_SAFE_CMPXCHG if (GUSA_RB || CPU_SH4A)
select ARCH_HAS_BINFMT_FLAT if !MMU
+ select ARCH_HAS_CURRENT_STACK_POINTER
select ARCH_HAS_GIGANTIC_PAGE
select ARCH_HAS_GCOV_PROFILE_ALL
select ARCH_HAS_PTE_SPECIAL