From 5745d97d88e46e21da5139cf49e50f88a6457d7f Mon Sep 17 00:00:00 2001 From: Salvatore Bonaccorso Date: Thu, 19 Jan 2017 12:55:51 +0100 Subject: [PATCH] [x86] KVM: Introduce segmented_write_std (CVE-2017-2584) --- debian/changelog | 1 + ...VM-x86-Introduce-segmented_write_std.patch | 61 +++++++++++++++++++ debian/patches/series | 1 + 3 files changed, 63 insertions(+) create mode 100644 debian/patches/bugfix/x86/KVM-x86-Introduce-segmented_write_std.patch diff --git a/debian/changelog b/debian/changelog index 54c7cf379..424587507 100644 --- a/debian/changelog +++ b/debian/changelog @@ -244,6 +244,7 @@ linux (4.9.4-1) UNRELEASED; urgency=medium * sysctl: Drop reference added by grab_header in proc_sys_readdir (CVE-2016-9191) * tmpfs: clear S_ISGID when setting posix ACLs + * [x86] KVM: Introduce segmented_write_std (CVE-2017-2584) -- Salvatore Bonaccorso Mon, 16 Jan 2017 09:26:13 +0100 diff --git a/debian/patches/bugfix/x86/KVM-x86-Introduce-segmented_write_std.patch b/debian/patches/bugfix/x86/KVM-x86-Introduce-segmented_write_std.patch new file mode 100644 index 000000000..b5ef81af9 --- /dev/null +++ b/debian/patches/bugfix/x86/KVM-x86-Introduce-segmented_write_std.patch @@ -0,0 +1,61 @@ +From: Steve Rutherford +Date: Wed, 11 Jan 2017 18:28:29 -0800 +Subject: KVM: x86: Introduce segmented_write_std +Origin: https://git.kernel.org/linus/129a72a0d3c8e139a04512325384fe5ac119e74d + +Introduces segemented_write_std. + +Switches from emulated reads/writes to standard read/writes in fxsave, +fxrstor, sgdt, and sidt. This fixes CVE-2017-2584, a longstanding +kernel memory leak. + +Since commit 283c95d0e389 ("KVM: x86: emulate FXSAVE and FXRSTOR", +2016-11-09), which is luckily not yet in any final release, this would +also be an exploitable kernel memory *write*! + +Reported-by: Dmitry Vyukov +Cc: stable@vger.kernel.org +Fixes: 96051572c819194c37a8367624b285be10297eca +Fixes: 283c95d0e3891b64087706b344a4b545d04a6e62 +Suggested-by: Paolo Bonzini +Signed-off-by: Steve Rutherford +Signed-off-by: Paolo Bonzini +[carnil: backport for 4.9, changes only before 283c95d0e389 in 4.10-rc1] +--- + arch/x86/kvm/emulate.c | 22 ++++++++++++++++++---- + 1 file changed, 18 insertions(+), 4 deletions(-) + +--- a/arch/x86/kvm/emulate.c ++++ b/arch/x86/kvm/emulate.c +@@ -791,6 +791,20 @@ static int segmented_read_std(struct x86 + return ctxt->ops->read_std(ctxt, linear, data, size, &ctxt->exception); + } + ++static int segmented_write_std(struct x86_emulate_ctxt *ctxt, ++ struct segmented_address addr, ++ void *data, ++ unsigned int size) ++{ ++ int rc; ++ ulong linear; ++ ++ rc = linearize(ctxt, addr, size, true, &linear); ++ if (rc != X86EMUL_CONTINUE) ++ return rc; ++ return ctxt->ops->write_std(ctxt, linear, data, size, &ctxt->exception); ++} ++ + /* + * Prefetch the remaining bytes of the instruction without crossing page + * boundary if they are not in fetch_cache yet. +@@ -3658,8 +3672,8 @@ static int emulate_store_desc_ptr(struct + } + /* Disable writeback. */ + ctxt->dst.type = OP_NONE; +- return segmented_write(ctxt, ctxt->dst.addr.mem, +- &desc_ptr, 2 + ctxt->op_bytes); ++ return segmented_write_std(ctxt, ctxt->dst.addr.mem, ++ &desc_ptr, 2 + ctxt->op_bytes); + } + + static int em_sgdt(struct x86_emulate_ctxt *ctxt) diff --git a/debian/patches/series b/debian/patches/series index 63dc38086..140cf35b2 100644 --- a/debian/patches/series +++ b/debian/patches/series @@ -97,6 +97,7 @@ features/all/securelevel/arm64-add-kernel-config-option-to-set-securelevel-wh.pa debian/i386-686-pae-pci-set-pci-nobios-by-default.patch bugfix/all/sysctl-Drop-reference-added-by-grab_header-in-proc_s.patch bugfix/all/tmpfs-clear-S_ISGID-when-setting-posix-ACLs.patch +bugfix/x86/KVM-x86-Introduce-segmented_write_std.patch # Fix exported symbol versions bugfix/ia64/revert-ia64-move-exports-to-definitions.patch