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SubjectRe: [PATCH 2/2] efi: show error messages only when loading certificates is failed
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Hi Ard,

On Fri, Dec 13, 2019 at 09:10:12AM +0000, Ard Biesheuvel wrote:
> On Fri, 13 Dec 2019 at 10:07, Lee, Chun-Yi <joeyli.kernel@gmail.com> wrote:
> >
> > When loading certificates list from EFI variables, the error
> > message and efi status code always be emitted to dmesg. It looks
> > ugly:
> >
> > [ 2.335031] Couldn't get size: 0x800000000000000e
> > [ 2.335032] Couldn't get UEFI MokListRT
> > [ 2.339985] Couldn't get size: 0x800000000000000e
> > [ 2.339987] Couldn't get UEFI dbx list
> >
> > This cosmetic patch moved the messages to the error handling code
> > path. And, it also shows the corresponding status string of status
> > code.
> >
>
> So what output do we get after applying this patch when those
> variables don't exist?
>

A "UEFI:xxxx list was not found" message will be exposed in dmesg
when kernel loglevel be set to debug. Otherwise there have no messages.

Thanks
Joey Lee

> > Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com>
> > ---
> > security/integrity/platform_certs/load_uefi.c | 40 ++++++++++++++-------------
> > 1 file changed, 21 insertions(+), 19 deletions(-)
> >
> > diff --git a/security/integrity/platform_certs/load_uefi.c b/security/integrity/platform_certs/load_uefi.c
> > index 81b19c52832b..b6c60fb3fb6c 100644
> > --- a/security/integrity/platform_certs/load_uefi.c
> > +++ b/security/integrity/platform_certs/load_uefi.c
> > @@ -1,4 +1,5 @@
> > // SPDX-License-Identifier: GPL-2.0
> > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> >
> > #include <linux/kernel.h>
> > #include <linux/sched.h>
> > @@ -39,7 +40,7 @@ static __init bool uefi_check_ignore_db(void)
> > * Get a certificate list blob from the named EFI variable.
> > */
> > static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid,
> > - unsigned long *size)
> > + unsigned long *size, const char *source)
> > {
> > efi_status_t status;
> > unsigned long lsize = 4;
> > @@ -48,23 +49,30 @@ static __init void *get_cert_list(efi_char16_t *name, efi_guid_t *guid,
> >
> > status = efi.get_variable(name, guid, NULL, &lsize, &tmpdb);
> > if (status != EFI_BUFFER_TOO_SMALL) {
> > - pr_err("Couldn't get size: 0x%lx\n", status);
> > - return NULL;
> > + if (status == EFI_NOT_FOUND) {
> > + pr_debug("%s list was not found\n", source);
> > + return NULL;
> > + }
> > + goto err;
> > }
> >
> > db = kmalloc(lsize, GFP_KERNEL);
> > - if (!db)
> > - return NULL;
> > + if (!db) {
> > + status = EFI_OUT_OF_RESOURCES;
> > + goto err;
> > + }
> >
> > status = efi.get_variable(name, guid, NULL, &lsize, db);
> > if (status != EFI_SUCCESS) {
> > kfree(db);
> > - pr_err("Error reading db var: 0x%lx\n", status);
> > - return NULL;
> > + goto err;
> > }
> >
> > *size = lsize;
> > return db;
> > +err:
> > + pr_err("Couldn't get %s list: %s\n", source, efi_status_to_str(status));
> > + return NULL;
> > }
> >
> > /*
> > @@ -153,10 +161,8 @@ static int __init load_uefi_certs(void)
> > * an error if we can't get them.
> > */
> > if (!uefi_check_ignore_db()) {
> > - db = get_cert_list(L"db", &secure_var, &dbsize);
> > - if (!db) {
> > - pr_err("MODSIGN: Couldn't get UEFI db list\n");
> > - } else {
> > + db = get_cert_list(L"db", &secure_var, &dbsize, "UEFI:db");
> > + if (db) {
> > rc = parse_efi_signature_list("UEFI:db",
> > db, dbsize, get_handler_for_db);
> > if (rc)
> > @@ -166,10 +172,8 @@ static int __init load_uefi_certs(void)
> > }
> > }
> >
> > - mok = get_cert_list(L"MokListRT", &mok_var, &moksize);
> > - if (!mok) {
> > - pr_info("Couldn't get UEFI MokListRT\n");
> > - } else {
> > + mok = get_cert_list(L"MokListRT", &mok_var, &moksize, "UEFI:MokListRT");
> > + if (mok) {
> > rc = parse_efi_signature_list("UEFI:MokListRT",
> > mok, moksize, get_handler_for_db);
> > if (rc)
> > @@ -177,10 +181,8 @@ static int __init load_uefi_certs(void)
> > kfree(mok);
> > }
> >
> > - dbx = get_cert_list(L"dbx", &secure_var, &dbxsize);
> > - if (!dbx) {
> > - pr_info("Couldn't get UEFI dbx list\n");
> > - } else {
> > + dbx = get_cert_list(L"dbx", &secure_var, &dbxsize, "UEFI:dbx");
> > + if (dbx) {
> > rc = parse_efi_signature_list("UEFI:dbx",
> > dbx, dbxsize,
> > get_handler_for_dbx);
> > --
> > 2.16.4
> >

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