efi: pstore: Request at most 512 bytes for variable names

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 commit 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>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

diff --git a/drivers/firmware/efi/efi-pstore.c b/drivers/firmware/efi/efi-pstore.c
index 833cbb995dd3f2bb1d447ecccd457aa03a3738a7..5b9dc26e6bcb963289debaee0084ed9494782d71 100644 (file)
--- a/drivers/firmware/efi/efi-pstore.c
+++ b/drivers/firmware/efi/efi-pstore.c
@@ -162,7 +162,15 @@ 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,