Re: [PATCH v1 1/5] powerpc/mm: sanity_check_fault() should work for all, not only BOOK3S
From: Nicholas Piggin <npiggin@gmail.com>
Date: 2020-09-08 08:43:59
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Excerpts from Christophe Leroy's message of August 7, 2020 3:15 am:
quoted hunk ↗ jump to hunk
The verification and message introduced by commit 374f3f5979f9 ("powerpc/mm/hash: Handle user access of kernel address gracefully") applies to all platforms, it should not be limited to BOOK3S. Make the BOOK3S version of sanity_check_fault() the one for all, and bail out earlier if not BOOK3S. Fixes: 374f3f5979f9 ("powerpc/mm/hash: Handle user access of kernel address gracefully") Signed-off-by: Christophe Leroy <redacted> --- arch/powerpc/mm/fault.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index 925a7231abb3..2efa34d7e644 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c@@ -303,7 +303,6 @@ static inline void cmo_account_page_fault(void) static inline void cmo_account_page_fault(void) { } #endif /* CONFIG_PPC_SMLPAR */ -#ifdef CONFIG_PPC_BOOK3S static void sanity_check_fault(bool is_write, bool is_user, unsigned long error_code, unsigned long address) {@@ -320,6 +319,9 @@ static void sanity_check_fault(bool is_write, bool is_user, return; } + if (!IS_ENABLED(CONFIG_PPC_BOOK3S)) + return;
Seems okay. Why is address == -1 special though? I guess it's because it may not be an exploit kernel reference but a buggy pointer underflow? In that case -1 doesn't seem like it would catch very much. Would it be better to test for high bit set for example ((long)address < 0) ? Anyway for your patch Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
quoted hunk ↗ jump to hunk
+ /* * For hash translation mode, we should never get a * PROTFAULT. Any update to pte to reduce access will result in us@@ -354,10 +356,6 @@ static void sanity_check_fault(bool is_write, bool is_user, WARN_ON_ONCE(error_code & DSISR_PROTFAULT); } -#else -static void sanity_check_fault(bool is_write, bool is_user, - unsigned long error_code, unsigned long address) { } -#endif /* CONFIG_PPC_BOOK3S */ /* * Define the correct "is_write" bit in error_code based-- 2.25.0