From 2ade0d60939bcd54197c133b03b460fe62a4ec47 Mon Sep 17 00:00:00 2001 From: Jarkko Sakkinen Date: Mon, 8 Feb 2021 00:14:01 +0200 Subject: x86/sgx: Maintain encl->refcount for each encl->mm_list entry This has been shown in tests: [ +0.000008] WARNING: CPU: 3 PID: 7620 at kernel/rcu/srcutree.c:374 cleanup_srcu_struct+0xed/0x100 This is essentially a use-after free, although SRCU notices it as an SRCU cleanup in an invalid context. == Background == SGX has a data structure (struct sgx_encl_mm) which keeps per-mm SGX metadata. This is separate from struct sgx_encl because, in theory, an enclave can be mapped from more than one mm. sgx_encl_mm includes a pointer back to the sgx_encl. This means that sgx_encl must have a longer lifetime than all of the sgx_encl_mm's that point to it. That's usually the case: sgx_encl_mm is freed only after the mmu_notifier is unregistered in sgx_release(). However, there's a race. If the process is exiting, sgx_mmu_notifier_release() can be called in parallel with sgx_release() instead of being called *by* it. The mmu_notifier path keeps encl_mm alive past when sgx_encl can be freed. This inverts the lifetime rules and means that sgx_mmu_notifier_release() can access a freed sgx_encl. == Fix == Increase encl->refcount when encl_mm->encl is established. Release this reference when encl_mm is freed. This ensures that encl outlives encl_mm. [ bp: Massage commit message. ] Fixes: 1728ab54b4be ("x86/sgx: Add a page reclaimer") Reported-by: Haitao Huang Signed-off-by: Jarkko Sakkinen Signed-off-by: Borislav Petkov Acked-by: Dave Hansen Link: https://lkml.kernel.org/r/20210207221401.29933-1-jarkko@kernel.org --- arch/x86/kernel/cpu/sgx/driver.c | 3 +++ arch/x86/kernel/cpu/sgx/encl.c | 5 +++++ 2 files changed, 8 insertions(+) diff --git a/arch/x86/kernel/cpu/sgx/driver.c b/arch/x86/kernel/cpu/sgx/driver.c index f2eac41bb4ff..8ce6d8371cfb 100644 --- a/arch/x86/kernel/cpu/sgx/driver.c +++ b/arch/x86/kernel/cpu/sgx/driver.c @@ -72,6 +72,9 @@ static int sgx_release(struct inode *inode, struct file *file) synchronize_srcu(&encl->srcu); mmu_notifier_unregister(&encl_mm->mmu_notifier, encl_mm->mm); kfree(encl_mm); + + /* 'encl_mm' is gone, put encl_mm->encl reference: */ + kref_put(&encl->refcount, sgx_encl_release); } kref_put(&encl->refcount, sgx_encl_release); diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c index ee50a5010277..f65564a94b9b 100644 --- a/arch/x86/kernel/cpu/sgx/encl.c +++ b/arch/x86/kernel/cpu/sgx/encl.c @@ -481,6 +481,9 @@ static void sgx_mmu_notifier_free(struct mmu_notifier *mn) { struct sgx_encl_mm *encl_mm = container_of(mn, struct sgx_encl_mm, mmu_notifier); + /* 'encl_mm' is going away, put encl_mm->encl reference: */ + kref_put(&encl_mm->encl->refcount, sgx_encl_release); + kfree(encl_mm); } @@ -534,6 +537,8 @@ int sgx_encl_mm_add(struct sgx_encl *encl, struct mm_struct *mm) if (!encl_mm) return -ENOMEM; + /* Grab a refcount for the encl_mm->encl reference: */ + kref_get(&encl->refcount); encl_mm->encl = encl; encl_mm->mm = mm; encl_mm->mmu_notifier.ops = &sgx_mmu_notifier_ops; -- cgit From 256b92af784d5043eeb7d559b6d5963dcc2ecb10 Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Mon, 8 Feb 2021 16:43:30 +0100 Subject: x86/build: Disable CET instrumentation in the kernel for 32-bit too Commit 20bf2b378729 ("x86/build: Disable CET instrumentation in the kernel") disabled CET instrumentation which gets added by default by the Ubuntu gcc9 and 10 by default, but did that only for 64-bit builds. It would still fail when building a 32-bit target. So disable CET for all x86 builds. Fixes: 20bf2b378729 ("x86/build: Disable CET instrumentation in the kernel") Reported-by: AC Signed-off-by: Borislav Petkov Acked-by: Josh Poimboeuf Tested-by: AC Link: https://lkml.kernel.org/r/YCCIgMHkzh/xT4ex@arch-chirva.localdomain --- arch/x86/Makefile | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 5857917f83ee..30920d70b48b 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -50,6 +50,9 @@ export BITS KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow KBUILD_CFLAGS += $(call cc-option,-mno-avx,) +# Intel CET isn't enabled in the kernel +KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none) + ifeq ($(CONFIG_X86_32),y) BITS := 32 UTS_MACHINE := i386 @@ -120,9 +123,6 @@ else KBUILD_CFLAGS += -mno-red-zone KBUILD_CFLAGS += -mcmodel=kernel - - # Intel CET isn't enabled in the kernel - KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none) endif ifdef CONFIG_X86_X32 -- cgit From 70245f86c109e0eafb92ea9653184c0e44b4b35c Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 10 Feb 2021 16:27:41 +0100 Subject: x86/pci: Create PCI/MSI irqdomain after x86_init.pci.arch_init() Invoking x86_init.irqs.create_pci_msi_domain() before x86_init.pci.arch_init() breaks XEN PV. The XEN_PV specific pci.arch_init() function overrides the default create_pci_msi_domain() which is obviously too late. As a consequence the XEN PV PCI/MSI allocation goes through the native path which runs out of vectors and causes malfunction. Invoke it after x86_init.pci.arch_init(). Fixes: 6b15ffa07dc3 ("x86/irq: Initialize PCI/MSI domain at PCI init time") Reported-by: Juergen Gross Signed-off-by: Thomas Gleixner Tested-by: Juergen Gross Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/87pn18djte.fsf@nanos.tec.linutronix.de --- arch/x86/pci/init.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/arch/x86/pci/init.c b/arch/x86/pci/init.c index 00bfa1ebad6c..0bb3b8b44e4e 100644 --- a/arch/x86/pci/init.c +++ b/arch/x86/pci/init.c @@ -9,16 +9,23 @@ in the right sequence from here. */ static __init int pci_arch_init(void) { - int type; - - x86_create_pci_msi_domain(); + int type, pcbios = 1; type = pci_direct_probe(); if (!(pci_probe & PCI_PROBE_NOEARLY)) pci_mmcfg_early_init(); - if (x86_init.pci.arch_init && !x86_init.pci.arch_init()) + if (x86_init.pci.arch_init) + pcbios = x86_init.pci.arch_init(); + + /* + * Must happen after x86_init.pci.arch_init(). Xen sets up the + * x86_init.irqs.create_pci_msi_domain there. + */ + x86_create_pci_msi_domain(); + + if (!pcbios) return 0; pci_pcbios_init(); -- cgit