62 lines
2.4 KiB
Diff
62 lines
2.4 KiB
Diff
From: Matt Fleming <matt.fleming@intel.com>
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Date: Fri, 1 Mar 2013 14:49:12 +0000
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Subject: efivars: explicitly calculate length of VariableName
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commit ec50bd32f1672d38ddce10fb1841cbfda89cfe9a upstream.
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It's not wise to assume VariableNameSize represents the length of
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VariableName, as not all firmware updates VariableNameSize in the same
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way (some don't update it at all if EFI_SUCCESS is returned). There
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are even implementations out there that update VariableNameSize with
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values that are both larger than the string returned in VariableName
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and smaller than the buffer passed to GetNextVariableName(), which
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resulted in the following bug report from Michael Schroeder,
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> On HP z220 system (firmware version 1.54), some EFI variables are
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> incorrectly named :
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>
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> ls -d /sys/firmware/efi/vars/*8be4d* | grep -v -- -8be returns
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> /sys/firmware/efi/vars/dbxDefault-pport8be4df61-93ca-11d2-aa0d-00e098032b8c
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> /sys/firmware/efi/vars/KEKDefault-pport8be4df61-93ca-11d2-aa0d-00e098032b8c
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> /sys/firmware/efi/vars/SecureBoot-pport8be4df61-93ca-11d2-aa0d-00e098032b8c
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> /sys/firmware/efi/vars/SetupMode-Information8be4df61-93ca-11d2-aa0d-00e098032b8c
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The issue here is that because we blindly use VariableNameSize without
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verifying its value, we can potentially read garbage values from the
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buffer containing VariableName if VariableNameSize is larger than the
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length of VariableName.
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Since VariableName is a string, we can calculate its size by searching
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for the terminating NULL character.
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Reported-by: Frederic Crozat <fcrozat@suse.com>
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Cc: Matthew Garrett <mjg59@srcf.ucam.org>
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Cc: Josh Boyer <jwboyer@redhat.com>
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Cc: Michael Schroeder <mls@suse.com>
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Cc: Lee, Chun-Yi <jlee@suse.com>
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Cc: Lingzhu Xiang <lxiang@redhat.com>
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Cc: Seiji Aguchi <seiji.aguchi@hds.com>
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Signed-off-by: Matt Fleming <matt.fleming@intel.com>
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[bwh: Apply only the part not included in 3.8.6]
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---
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drivers/firmware/efivars.c | 32 +++++++++++++++++++++++++++++++-
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1 file changed, 31 insertions(+), 1 deletion(-)
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--- a/drivers/firmware/efivars.c
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+++ b/drivers/firmware/efivars.c
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@@ -1783,10 +1783,13 @@ static void efivar_update_sysfs_entries(
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if (!found) {
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kfree(variable_name);
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break;
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- } else
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+ } else {
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+ variable_name_size = var_name_strnsize(variable_name,
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+ variable_name_size);
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efivar_create_sysfs_entry(efivars,
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variable_name_size,
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variable_name, &vendor);
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+ }
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}
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}
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