Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757715Ab3CFLTX (ORCPT ); Wed, 6 Mar 2013 06:19:23 -0500 Received: from arkanian.console-pimps.org ([212.110.184.194]:43718 "EHLO arkanian.console-pimps.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754142Ab3CFLTS (ORCPT ); Wed, 6 Mar 2013 06:19:18 -0500 Message-ID: <1362568750.15011.24.camel@mfleming-mobl1.ger.corp.intel.com> Subject: Re: [PATCH] efivarfs: fix abnormal GUID in variable name by using strcpy to replace null with dash From: Matt Fleming To: joeyli Cc: linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, Michael Schroeder , Josh Boyer , Peter Jones , Matthew Garrett , Frederic Crozat Date: Wed, 06 Mar 2013 11:19:10 +0000 In-Reply-To: <1362555258.23932.573.camel@linux-s257.site> References: <1362108018-13117-1-git-send-email-jlee@suse.com> <1362151068.2842.440.camel@mfleming-mobl1.ger.corp.intel.com> <1362155493.2842.446.camel@mfleming-mobl1.ger.corp.intel.com> <1362181299.23932.168.camel@linux-s257.site> <1362555258.23932.573.camel@linux-s257.site> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.4 (3.4.4-2.fc17) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8485 Lines: 227 On Wed, 2013-03-06 at 15:34 +0800, joeyli wrote: > Hi Matt, > > 於 六，2013-03-02 於 07:41 +0800，joeyli 提到： > > 於 五，2013-03-01 於 16:31 +0000，Matt Fleming 提到： > > > On Fri, 2013-03-01 at 15:17 +0000, Matt Fleming wrote: > > > > On Fri, 2013-03-01 at 11:20 +0800, Lee, Chun-Yi wrote: > > > > > From: Michael Schroeder > > > > > > > > > > On HP z220 system (firmware version 1.54), some EFI variables are incorrectly > > > > > named : > > > > > > > > > > ls -d /sys/firmware/efi/vars/*8be4d* | grep -v -- -8be returns > > > > > /sys/firmware/efi/vars/dbxDefault-pport8be4df61-93ca-11d2-aa0d-00e098032b8c > > > > > /sys/firmware/efi/vars/KEKDefault-pport8be4df61-93ca-11d2-aa0d-00e098032b8c > > > > > /sys/firmware/efi/vars/SecureBoot-pport8be4df61-93ca-11d2-aa0d-00e098032b8c > > > > > /sys/firmware/efi/vars/SetupMode-Information8be4df61-93ca-11d2-aa0d-00e098032b8c > > > > > > > > > > That causes by the following statement in efivar_create_sysfs_entry function: > > > > > > > > > > *(short_name + strlen(short_name)) = '-'; > > > > > efi_guid_unparse(vendor_guid, short_name + strlen(short_name)); > > > > > > > > > > The trailing \0 is overwritten with '-', but the next char doesn't seem to be a \0 > > > > > as well for HP. So, the second strlen return the point of next '\0', causes there > > > > > have garbage string attached before GUID. > > > > > > > > > > Tested on On HP z220. > > > > > > > > What's more likely happening here is that GetNextVariable() is broken on > > > > this HP firmware and variable_name_size is too big for the given > > > > variable in variable_name. We've seen other reports of similar bugs, > > > > > > > > https://bugzilla.kernel.org/show_bug.cgi?id=47631 > > > > > > > > > > > > Could someone try this patch against Linus' tree? > > > > > > Urgh, and here's a version that isn't utterly, utterly broken... > > > > Thanks for Matt's patch, we will try it! > > > > Joey Lee > > Frederic confirmed your patch works to him for fix issue on HP machine. > > Tested-by: Frederic Crozat > > But, I suggest we just use the length with NULL in variable_name but not > VariableNameSize that was returned by GetNextVariableName. > > My thinking is following... > > > > > > > > > --- > > > > > > >From 4b2ef72bca72039717efe4570ec858a86d565b34 Mon Sep 17 00:00:00 2001 > > > From: Matt Fleming > > > Date: Fri, 1 Mar 2013 14:49:12 +0000 > > > Subject: [PATCH] efivars: Sanitise string length returned by > > > GetNextVariableName() > > > > > > Some buggy firmware implementations return a string length from > > > GetNextVariableName() that is actually larger than the string in > > > 'variable_name', as Michael Schroeder writes, > > > > > > > On HP z220 system (firmware version 1.54), some EFI variables are > > > > incorrectly named : > > > > > > > > ls -d /sys/firmware/efi/vars/*8be4d* | grep -v -- -8be returns > > > > /sys/firmware/efi/vars/dbxDefault-pport8be4df61-93ca-11d2-aa0d-00e098032b8c > > > > /sys/firmware/efi/vars/KEKDefault-pport8be4df61-93ca-11d2-aa0d-00e098032b8c > > > > /sys/firmware/efi/vars/SecureBoot-pport8be4df61-93ca-11d2-aa0d-00e098032b8c > > > > /sys/firmware/efi/vars/SetupMode-Information8be4df61-93ca-11d2-aa0d-00e098032b8c > > > > > > Since 'variable_name' is a string, we can validate its size by > > > searching for the terminating NULL character. > > > > > > Reported-by: Frederic Crozat > > > Cc: Matthew Garrett > > > Cc: Josh Boyer > > > Cc: Michael Schroeder > > > Cc: Lee, Chun-Yi > > > Cc: Lingzhu Xiang > > > Signed-off-by: Matt Fleming > > > --- > > > drivers/firmware/efivars.c | 30 ++++++++++++++++++++++++++++++ > > > 1 file changed, 30 insertions(+) > > > > > > diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c > > > index 7320bf8..ab477b8 100644 > > > --- a/drivers/firmware/efivars.c > > > +++ b/drivers/firmware/efivars.c > > > @@ -1895,6 +1895,33 @@ void unregister_efivars(struct efivars *efivars) > > > } > > > EXPORT_SYMBOL_GPL(unregister_efivars); > > > > > > +/* > > > + * Sanity check size of a variable name. > > > + */ > > > +static unsigned long sanity_check_size(efi_char16_t *variable_name, > > > + unsigned long variable_name_size) > > > +{ > > > + unsigned long len; > > > + efi_char16_t c; > > > + > > > + /* > > > + * The variable name is, by definition, a NULL-terminated > > > + * string, so make absolutely sure that variable_name_size is > > > + * the value we expect it to be. If not, return the real size. > > > + */ > > > + for (len = 2; len <= variable_name_size; len += sizeof(c)) { > > > + c = variable_name[(len / sizeof(c)) - 1]; > > > + if (!c) > > > + break; > > > + } > > > + > > We just direct return the len here but don't need compare with > variable_name_size. > > return len; > > > > + > > > + if (len != variable_name_size) > > > + printk(KERN_WARNING "efivars: bogus variable_name_size: %lu %lu\n", len, variable_name_size); > > > + > > > + return min(len, variable_name_size); > > > +} > > > + > > In UEFI 2.3.1 spec: > > VariableNameSize The size of the VariableName buffer > > Note that if EFI_BUFFER_TOO_SMALL is returned, the VariableName buffer > was too small for the next variable. When such an error occurs, the > VariableNameSize is updated to reflect the size of buffer needed. In all > cases when calling GetNextVariableName() the VariableNameSize must not > exceed the actual buffer size that was allocated for VariableName. > > > Per spec, VariableNameSize will updated to 'the size of buffer needed' > when EFI_BUFFER_TOO_SMALL, but spec doesn't mention VariableNameSize > will also updated when EFI_SUCCESS. That means 'VariableNameSize = 1024' > when EFI_SUCCESS is not a bogus value. > > > > int register_efivars(struct efivars *efivars, > > > const struct efivar_operations *ops, > > > struct kobject *parent_kobj) > > > @@ -1941,8 +1968,11 @@ int register_efivars(struct efivars *efivars, > > > status = ops->get_next_variable(&variable_name_size, > > > variable_name, > > > &vendor_guid); > > > + > > > switch (status) { > > > case EFI_SUCCESS: > > > + variable_name_size = sanity_check_size(variable_name, > > > + variable_name_size); > > > efivar_create_sysfs_entry(efivars, > > > variable_name_size, > > > variable_name, > > > > Due to variable_name_size could be 1024, so I suggest direct feed the > length of variable_name to efivar_create_sysfs_entry since we are need > to count the length. > > This is a simply diff for my think: > > > diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c > index 7320bf8..99a4f9f 100644 > --- a/drivers/firmware/efivars.c > +++ b/drivers/firmware/efivars.c > @@ -1895,6 +1895,21 @@ void unregister_efivars(struct efivars *efivars) > } > EXPORT_SYMBOL_GPL(unregister_efivars); > > +static unsigned long variable_name_length(efi_char16_t *variable_name) > +{ > + unsigned long len; > + efi_char16_t c; > + > + len = 2; > + do { > + c = variable_name[len / sizeof(c) - 1]; > + if (c) > + len += sizeof(c); > + } while (c); > + > + return len; > +} > + > int register_efivars(struct efivars *efivars, > const struct efivar_operations *ops, > struct kobject *parent_kobj) > @@ -1944,7 +1959,7 @@ int register_efivars(struct efivars *efivars, > switch (status) { > case EFI_SUCCESS: > efivar_create_sysfs_entry(efivars, > - variable_name_size, > + variable_name_length(variable_name), > variable_name, > &vendor_guid); > break; > Hmm.. the reason I didn't implement the patch this way is because I do think it's important to make sure we don't go out of bounds looking for the terminating NULL, i.e. you need a 'len < variable_name_size' check somewhere. Care to update and resend your patch, ensuring we don't inspect more than variable_name_size characters? Also, which machine did you see this behaviour on? -- Matt Fleming, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/