Arm64 regression fix - rhbz 1788624

2 files changed, 122 insertions, 0 deletions

diff --git a/arm64-revert-support-for-execute-only-user-mappings.patch b/arm64-revert-support-for-execute-only-user-mappings.patch
new file mode 100644
index 000000000..8ca23e6c9
--- /dev/null
+++ b/arm64-revert-support-for-execute-only-user-mappings.patch
@@ -0,0 +1,119 @@
+From 24cecc37746393432d994c0dbc251fb9ac7c5d72 Mon Sep 17 00:00:00 2001
+From: Catalin Marinas <catalin.marinas@arm.com>
+Date: Mon, 6 Jan 2020 14:35:39 +0000
+Subject: arm64: Revert support for execute-only user mappings
+
+The ARMv8 64-bit architecture supports execute-only user permissions by
+clearing the PTE_USER and PTE_UXN bits, practically making it a mostly
+privileged mapping but from which user running at EL0 can still execute.
+
+The downside, however, is that the kernel at EL1 inadvertently reading
+such mapping would not trip over the PAN (privileged access never)
+protection.
+
+Revert the relevant bits from commit cab15ce604e5 ("arm64: Introduce
+execute-only page access permissions") so that PROT_EXEC implies
+PROT_READ (and therefore PTE_USER) until the architecture gains proper
+support for execute-only user mappings.
+
+Fixes: cab15ce604e5 ("arm64: Introduce execute-only page access permissions")
+Cc: <stable@vger.kernel.org> # 4.9.x-
+Acked-by: Will Deacon <will@kernel.org>
+Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+---
+ arch/arm64/include/asm/pgtable-prot.h |  5 ++---
+ arch/arm64/include/asm/pgtable.h      | 10 +++-------
+ arch/arm64/mm/fault.c                 |  2 +-
+ mm/mmap.c                             |  6 ------
+ 4 files changed, 6 insertions(+), 17 deletions(-)
+
+diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h
+index 8dc6c5c..baf52ba 100644
+--- a/arch/arm64/include/asm/pgtable-prot.h
++++ b/arch/arm64/include/asm/pgtable-prot.h
+@@ -85,13 +85,12 @@
+ #define PAGE_SHARED_EXEC	__pgprot(_PAGE_DEFAULT | PTE_USER | PTE_RDONLY | PTE_NG | PTE_PXN | PTE_WRITE)
+ #define PAGE_READONLY		__pgprot(_PAGE_DEFAULT | PTE_USER | PTE_RDONLY | PTE_NG | PTE_PXN | PTE_UXN)
+ #define PAGE_READONLY_EXEC	__pgprot(_PAGE_DEFAULT | PTE_USER | PTE_RDONLY | PTE_NG | PTE_PXN)
+-#define PAGE_EXECONLY		__pgprot(_PAGE_DEFAULT | PTE_RDONLY | PTE_NG | PTE_PXN)
+ 
+ #define __P000  PAGE_NONE
+ #define __P001  PAGE_READONLY
+ #define __P010  PAGE_READONLY
+ #define __P011  PAGE_READONLY
+-#define __P100  PAGE_EXECONLY
++#define __P100  PAGE_READONLY_EXEC
+ #define __P101  PAGE_READONLY_EXEC
+ #define __P110  PAGE_READONLY_EXEC
+ #define __P111  PAGE_READONLY_EXEC
+@@ -100,7 +99,7 @@
+ #define __S001  PAGE_READONLY
+ #define __S010  PAGE_SHARED
+ #define __S011  PAGE_SHARED
+-#define __S100  PAGE_EXECONLY
++#define __S100  PAGE_READONLY_EXEC
+ #define __S101  PAGE_READONLY_EXEC
+ #define __S110  PAGE_SHARED_EXEC
+ #define __S111  PAGE_SHARED_EXEC
+diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
+index 5d15b47..cd5de0e 100644
+--- a/arch/arm64/include/asm/pgtable.h
++++ b/arch/arm64/include/asm/pgtable.h
+@@ -96,12 +96,8 @@ extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
+ #define pte_dirty(pte)		(pte_sw_dirty(pte) || pte_hw_dirty(pte))
+ 
+ #define pte_valid(pte)		(!!(pte_val(pte) & PTE_VALID))
+-/*
+- * Execute-only user mappings do not have the PTE_USER bit set. All valid
+- * kernel mappings have the PTE_UXN bit set.
+- */
+ #define pte_valid_not_user(pte) \
+-	((pte_val(pte) & (PTE_VALID | PTE_USER | PTE_UXN)) == (PTE_VALID | PTE_UXN))
++	((pte_val(pte) & (PTE_VALID | PTE_USER)) == PTE_VALID)
+ #define pte_valid_young(pte) \
+ 	((pte_val(pte) & (PTE_VALID | PTE_AF)) == (PTE_VALID | PTE_AF))
+ #define pte_valid_user(pte) \
+@@ -117,8 +113,8 @@ extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
+ 
+ /*
+  * p??_access_permitted() is true for valid user mappings (subject to the
+- * write permission check) other than user execute-only which do not have the
+- * PTE_USER bit set. PROT_NONE mappings do not have the PTE_VALID bit set.
++ * write permission check). PROT_NONE mappings do not have the PTE_VALID bit
++ * set.
+  */
+ #define pte_access_permitted(pte, write) \
+ 	(pte_valid_user(pte) && (!(write) || pte_write(pte)))
+diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
+index 077b02a..85566d3 100644
+--- a/arch/arm64/mm/fault.c
++++ b/arch/arm64/mm/fault.c
+@@ -445,7 +445,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
+ 	const struct fault_info *inf;
+ 	struct mm_struct *mm = current->mm;
+ 	vm_fault_t fault, major = 0;
+-	unsigned long vm_flags = VM_READ | VM_WRITE;
++	unsigned long vm_flags = VM_READ | VM_WRITE | VM_EXEC;
+ 	unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
+ 
+ 	if (kprobe_page_fault(regs, esr))
+diff --git a/mm/mmap.c b/mm/mmap.c
+index 9c64852..71e4ffc 100644
+--- a/mm/mmap.c
++++ b/mm/mmap.c
+@@ -90,12 +90,6 @@ static void unmap_region(struct mm_struct *mm,
+  * MAP_PRIVATE	r: (no) no	r: (yes) yes	r: (no) yes	r: (no) yes
+  *		w: (no) no	w: (no) no	w: (copy) copy	w: (no) no
+  *		x: (no) no	x: (no) yes	x: (no) yes	x: (yes) yes
+- *
+- * On arm64, PROT_EXEC has the following behaviour for both MAP_SHARED and
+- * MAP_PRIVATE:
+- *								r: (no) no
+- *								w: (no) no
+- *								x: (yes) yes
+  */
+ pgprot_t protection_map[16] __ro_after_init = {
+ 	__P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
+-- 
+cgit v1.1
diff --git a/kernel.spec b/kernel.spec
index 7eb2bf36f..b9efdcfa1 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -598,6 +598,9 @@ Patch531: 0001-crypto-ccp-Release-all-allocated-memory-if-sha-type-.patch
 # CVE-2019-18809 rhbz 1777449 1777451
 Patch532: 0001-media-usb-fix-memory-leak-in-af9005_identify_state.patch
 
+# Arm64 regression fix - rhbz 1788624
+Patch533: arm64-revert-support-for-execute-only-user-mappings.patch
+
 # ALSA code from v5.5 (Intel ASoC Sound Open Firmware driver support)
 Patch600: alsa-5.5.patch