From: Tim Schumacher <timschumi@gmx.de>
To: linux-efi@vger.kernel.org
Cc: Tim Schumacher <timschumi@gmx.de>,
Kees Cook <keescook@chromium.org>,
Tony Luck <tony.luck@intel.com>,
"Guilherme G. Piccoli" <gpiccoli@igalia.com>,
Ard Biesheuvel <ardb@kernel.org>,
linux-hardening@vger.kernel.org
Subject: [PATCH 1/3] efi: pstore: Request at most 512 bytes for variable names
Date: Fri, 15 Mar 2024 01:25:58 +0100 [thread overview]
Message-ID: <20240315002616.422802-1-timschumi@gmx.de> (raw)
Work around a quirk in a few old (2011-ish) UEFI implementations, where
a call to `GetNextVariableName` with a buffer size larger than 512 bytes
will always return EFI_INVALID_PARAMETER.
This was already done to efivarfs in f45812cc23fb ("efivarfs: Request at
most 512 bytes for variable names"), but the second copy of the variable
iteration implementation was overlooked.
Signed-off-by: Tim Schumacher <timschumi@gmx.de>
---
I CC'd the pstore people and linux-hardening mailing list because
get_maintainer.pl suggested to do so. Apologies in case this was the
incorrect decision, this is a very non-pstore-specific patch after all.
I have taken the liberty of adding a TODO for the future, the actual
refactor can follow at some point down the line.
---
drivers/firmware/efi/efi-pstore.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/drivers/firmware/efi/efi-pstore.c b/drivers/firmware/efi/efi-pstore.c
index e7b9ec6f8a86..f0ceb5702d21 100644
--- a/drivers/firmware/efi/efi-pstore.c
+++ b/drivers/firmware/efi/efi-pstore.c
@@ -135,7 +135,15 @@ static ssize_t efi_pstore_read(struct pstore_record *record)
efi_status_t status;
for (;;) {
- varname_size = 1024;
+ /*
+ * A small set of old UEFI implementations reject sizes
+ * above a certain threshold, the lowest seen in the wild
+ * is 512.
+ *
+ * TODO: Commonize with the iteration implementation in
+ * fs/efivarfs to keep all the quirks in one place.
+ */
+ varname_size = 512;
/*
* If this is the first read() call in the pstore enumeration,
--
2.44.0
next reply other threads:[~2024-03-15 0:27 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-15 0:25 Tim Schumacher [this message]
2024-03-15 9:16 ` [PATCH 1/3] efi: pstore: Request at most 512 bytes for variable names Ard Biesheuvel
2024-03-15 19:02 ` Tim Schumacher
2024-03-15 19:45 ` Guilherme G. Piccoli
2024-03-29 7:34 ` Ard Biesheuvel
2024-03-29 21:32 ` Guilherme G. Piccoli
2024-03-28 20:50 ` [PATCH v2 1/4] " Tim Schumacher
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