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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id z6sm24659552pfg.68.2020.08.18.12.32.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Aug 2020 12:32:37 -0700 (PDT) Date: Tue, 18 Aug 2020 12:32:36 -0700 From: Kees Cook To: Christoph Hellwig Cc: Al Viro , Michael Ellerman , x86@kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 06/11] lkdtm: disable set_fs-based tests for !CONFIG_SET_FS Message-ID: <202008181228.D2DBEC6C6@keescook> References: <20200817073212.830069-1-hch@lst.de> <20200817073212.830069-7-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200817073212.830069-7-hch@lst.de> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 17, 2020 at 09:32:07AM +0200, Christoph Hellwig wrote: > Once we can't manipulate the address limit, we also can't test what > happens when the manipulation is abused. > > Signed-off-by: Christoph Hellwig > --- > drivers/misc/lkdtm/bugs.c | 2 ++ > drivers/misc/lkdtm/core.c | 4 ++++ > drivers/misc/lkdtm/usercopy.c | 2 ++ > 3 files changed, 8 insertions(+) > > diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c > index 4dfbfd51bdf774..66f1800b1cb82d 100644 > --- a/drivers/misc/lkdtm/bugs.c > +++ b/drivers/misc/lkdtm/bugs.c > @@ -312,6 +312,7 @@ void lkdtm_CORRUPT_LIST_DEL(void) > pr_err("list_del() corruption not detected!\n"); > } > > +#ifdef CONFIG_SET_FS > /* Test if unbalanced set_fs(KERNEL_DS)/set_fs(USER_DS) check exists. */ > void lkdtm_CORRUPT_USER_DS(void) > { > @@ -321,6 +322,7 @@ void lkdtm_CORRUPT_USER_DS(void) > /* Make sure we do not keep running with a KERNEL_DS! */ > force_sig(SIGKILL); > } > +#endif Please let the test defined, but it should XFAIL with a message about the CONFIG (see similar ifdefs in lkdtm). > /* Test that VMAP_STACK is actually allocating with a leading guard page */ > void lkdtm_STACK_GUARD_PAGE_LEADING(void) > diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c > index a5e344df916632..aae08b33a7ee2a 100644 > --- a/drivers/misc/lkdtm/core.c > +++ b/drivers/misc/lkdtm/core.c > @@ -112,7 +112,9 @@ static const struct crashtype crashtypes[] = { > CRASHTYPE(CORRUPT_STACK_STRONG), > CRASHTYPE(CORRUPT_LIST_ADD), > CRASHTYPE(CORRUPT_LIST_DEL), > +#ifdef CONFIG_SET_FS > CRASHTYPE(CORRUPT_USER_DS), > +#endif > CRASHTYPE(STACK_GUARD_PAGE_LEADING), > CRASHTYPE(STACK_GUARD_PAGE_TRAILING), > CRASHTYPE(UNSET_SMEP), > @@ -172,7 +174,9 @@ static const struct crashtype crashtypes[] = { > CRASHTYPE(USERCOPY_STACK_FRAME_FROM), > CRASHTYPE(USERCOPY_STACK_BEYOND), > CRASHTYPE(USERCOPY_KERNEL), > +#ifdef CONFIG_SET_FS > CRASHTYPE(USERCOPY_KERNEL_DS), > +#endif > CRASHTYPE(STACKLEAK_ERASING), > CRASHTYPE(CFI_FORWARD_PROTO), Then none of these are needed. > #ifdef CONFIG_X86_32 Hmpf, this ifdef was missed in ae56942c1474 ("lkdtm: Make arch-specific tests always available"). I will fix that. > diff --git a/drivers/misc/lkdtm/usercopy.c b/drivers/misc/lkdtm/usercopy.c > index b833367a45d053..4b632fe79ab6bb 100644 > --- a/drivers/misc/lkdtm/usercopy.c > +++ b/drivers/misc/lkdtm/usercopy.c > @@ -325,6 +325,7 @@ void lkdtm_USERCOPY_KERNEL(void) > vm_munmap(user_addr, PAGE_SIZE); > } > > +#ifdef CONFIG_SET_FS > void lkdtm_USERCOPY_KERNEL_DS(void) > { > char __user *user_ptr = > @@ -339,6 +340,7 @@ void lkdtm_USERCOPY_KERNEL_DS(void) > pr_err("copy_to_user() to noncanonical address succeeded!?\n"); > set_fs(old_fs); > } > +#endif (Same here, please.) > > void __init lkdtm_usercopy_init(void) > { > -- > 2.28.0 > -- Kees Cook