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From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
To: linuxppc-dev@lists.ozlabs.org, mpe@ellerman.id.au
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
	linuxram@us.ibm.com, npiggin@gmail.com
Subject: [RFC PATCH 20/25] powerpc/book3s64/kuap: Improve error reporting with KUAP
Date: Mon, 27 Apr 2020 13:35:01 +0530	[thread overview]
Message-ID: <20200427080507.1626327-21-aneesh.kumar@linux.ibm.com> (raw)
In-Reply-To: <20200427080507.1626327-1-aneesh.kumar@linux.ibm.com>

With hash translation use DSISR_KEYFAULT to identify a wrong access.
With Radix we look at the AMR value and type of fault.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
 arch/powerpc/include/asm/book3s/64/kup.h |  7 ------
 arch/powerpc/mm/fault.c                  | 27 +++++++++++++++++++++++-
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/kup.h b/arch/powerpc/include/asm/book3s/64/kup.h
index 590c1d9455d1..f564d909e195 100644
--- a/arch/powerpc/include/asm/book3s/64/kup.h
+++ b/arch/powerpc/include/asm/book3s/64/kup.h
@@ -280,13 +280,6 @@ static inline void restore_user_access(unsigned long flags)
 	set_kuap(flags);
 }
 
-static inline bool
-bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
-{
-	return WARN(mmu_has_feature(MMU_FTR_KUAP) &&
-		    (regs->kuap & (is_write ? AMR_KUAP_BLOCK_WRITE : AMR_KUAP_BLOCK_READ)),
-		    "Bug: %s fault blocked by AMR!", is_write ? "Write" : "Read");
-}
 #else /* CONFIG_PPC_KUAP */
 static inline void kuap_restore_amr(struct pt_regs *regs)
 {
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 84af6c8eecf7..4f866b11512c 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -198,6 +198,31 @@ static int mm_fault_error(struct pt_regs *regs, unsigned long addr,
 	return 0;
 }
 
+#define RADIX_KUAP_BLOCK_READ	UL(0x4000000000000000)
+#define RADIX_KUAP_BLOCK_WRITE	UL(0x8000000000000000)
+
+static bool bad_kuap_fault(struct pt_regs *regs, unsigned long address,
+			   bool is_write, unsigned long error_code)
+{
+	if (!mmu_has_feature(MMU_FTR_KUAP))
+		return false;
+
+	if (radix_enabled()) {
+		/*
+		 * Will be a storage protection fault.
+		 * Only check the details of AMR[0]
+		 */
+		return WARN((regs->kuap & (is_write ? RADIX_KUAP_BLOCK_WRITE : RADIX_KUAP_BLOCK_READ)),
+			    "Bug: %s fault blocked by AMR!", is_write ? "Write" : "Read");
+	}
+	/*
+	 * We don't want to WARN here because userspace can setup
+	 * keys such that a kernel access to user address can cause
+	 * fault
+	 */
+	return !!(error_code & DSISR_KEYFAULT);
+}
+
 /* Is this a bad kernel fault ? */
 static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code,
 			     unsigned long address, bool is_write)
@@ -233,7 +258,7 @@ static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code,
 
 	// Read/write fault in a valid region (the exception table search passed
 	// above), but blocked by KUAP is bad, it can never succeed.
-	if (bad_kuap_fault(regs, address, is_write))
+	if (bad_kuap_fault(regs, address, is_write, error_code))
 		return true;
 
 	// What's left? Kernel fault on user in well defined regions (extable
-- 
2.25.3


  parent reply	other threads:[~2020-04-27  8:53 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-27  8:04 [RFC PATCH 00/25] Kernel userspace access/execution prevention with hash translation Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 01/25] powerpc/book3s64/pkeys: Mark all the pkeys above max pkey as reserved Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 02/25] powerpc/book3s64/pkeys: Enable MMU_FTR_PKEY Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 03/25] powerpc/book3s64/kuep: Add MMU_FTR_KUEP Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 04/25] powerpc/book3s64/pkeys: Use execute_pkey_disable static key Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 05/25] powerpc/book3s64/pkeys: Use MMU_FTR_PKEY instead of pkey_disabled " Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 06/25] powerpc/book3s64/kuap: Move KUAP related function outside radix Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 07/25] powerpc/book3s64/kuep: Move KUEP " Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 08/25] powerpc/book3s64/kuap: Rename MMU_FTR_RADIX_KUAP to MMU_FTR_KUAP Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 09/25] powerpc/book3s64/kuap/kuep: Make KUAP and KUEP a subfeature of PPC_MEM_KEYS Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 10/25] powerpc/book3s64/kuap: Move UAMOR setup to key init function Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 11/25] powerpc/book3s64/kuap: Use Key 3 for kernel mapping with hash translation Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 12/25] powerpc/exec: Set thread.regs early during exec Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 13/25] powerpc/book3s64/pkeys: Store/restore userspace AMR correctly on entry and exit from kernel Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 14/25] powerpc/book3s64/kuep: Store/restore userspace IAMR " Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 15/25] powerpc/book3s64/pkeys: Inherit correctly on fork Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 16/25] powerpc/book3s64/pkeys: Reset userspace AMR correctly on exec Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 17/25] powerpc/ptrace-view: Use pt_regs values instead of thread_struct based one Aneesh Kumar K.V
2020-04-27  8:04 ` [RFC PATCH 18/25] powerpc/book3s64/pkeys: Don't update SPRN_AMR when in kernel mode Aneesh Kumar K.V
2020-04-27  8:05 ` [RFC PATCH 19/25] powerpc/book3s64/kuap: Restrict access to userspace based on userspace AMR Aneesh Kumar K.V
2020-04-27  8:05 ` Aneesh Kumar K.V [this message]
2020-04-27  8:05 ` [RFC PATCH 21/25] powerpc/book3s64/kuap: Use Key 3 to implement KUAP with hash translation Aneesh Kumar K.V
2020-04-27  8:05 ` [RFC PATCH 22/25] powerpc/book3s64/kuep: Use Key 3 to implement KUEP " Aneesh Kumar K.V
2020-04-27  8:05 ` [RFC PATCH 23/25] powerpc/book3s64/hash/kuap: Enable kuap on hash Aneesh Kumar K.V
2020-04-27  8:05 ` [RFC PATCH 24/25] powerpc/book3s64/hash/kuep: Enable KUEP " Aneesh Kumar K.V
2020-04-27  8:05 ` [RFC PATCH 25/25] powerpc/book3s64/keys: Print information during boot Aneesh Kumar K.V

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