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 <mls@xxxxxxxx> > > > > 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... --- >From 4b2ef72bca72039717efe4570ec858a86d565b34 Mon Sep 17 00:00:00 2001 From: Matt Fleming <matt.fleming@xxxxxxxxx> 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 <fcrozat@xxxxxxxx> Cc: Matthew Garrett <mjg59@xxxxxxxxxxxxx> Cc: Josh Boyer <jwboyer@xxxxxxxxxx> Cc: Michael Schroeder <mls@xxxxxxxx> Cc: Lee, Chun-Yi <jlee@xxxxxxxx> Cc: Lingzhu Xiang <lxiang@xxxxxxxxxx> Signed-off-by: Matt Fleming <matt.fleming@xxxxxxxxx> --- 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; + } + + + 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); +} + 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, -- 1.7.11.7 -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
