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? --- >From fe38d6f69c889b0f95c5548c724633aa58c2c99f 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 | 35 ++++++++++++++++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-) diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c index 7320bf8..b5af292 100644 --- a/drivers/firmware/efivars.c +++ b/drivers/firmware/efivars.c @@ -1653,6 +1653,33 @@ static bool variable_is_present(efi_char16_t *variable_name, efi_guid_t *vendor) return found; } +/* + * Sanity check string length of a variable name. + */ +static unsigned long sanity_check_strlen(efi_char16_t *variable_name, + unsigned long variable_name_size) +{ + efi_char16_t c; + unsigned long len; + + /* + * 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, use whichever size is + * smaller. + */ + for (len = 1; len <= variable_name_size; len++) { + c = variable_name[len - 1]; + if (!c) + break; + } + + if (len != variable_name_size) + printk(KERN_WARNING "efivars: bogus variable_name_size\n"); + + return min(len, variable_name_size); +} + static void efivar_update_sysfs_entries(struct work_struct *work) { struct efivars *efivars = &__efivars; @@ -1693,10 +1720,13 @@ static void efivar_update_sysfs_entries(struct work_struct *work) if (!found) { kfree(variable_name); break; - } else + } else { + variable_name_size = sanity_check_strlen(variable_name, + variable_name_size); efivar_create_sysfs_entry(efivars, variable_name_size, variable_name, &vendor); + } } } @@ -1941,8 +1971,11 @@ 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_strlen(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
