[tip: efi/urgent] efi/libstub: Handle unterminated cmdline

[tip-bot2 for Arvind Sankar]

The following commit has been merged into the efi/urgent branch of tip:

Commit-ID:     8a8a3237a78cbc0557f0eb16a89f16d616323e99
Gitweb:        https://git.kernel.org/tip/8a8a3237a78cbc0557f0eb16a89f16d616323e99
Author:        Arvind Sankar <nivedita@xxxxxxxxxxxx>
AuthorDate:    Thu, 13 Aug 2020 14:58:11 -04:00
Committer:     Ard Biesheuvel <ardb@xxxxxxxxxx>
CommitterDate: Thu, 20 Aug 2020 11:18:58 +02:00

efi/libstub: Handle unterminated cmdline

Make the command line parsing more robust, by handling the case it is
not NUL-terminated.

Use strnlen instead of strlen, and make sure that the temporary copy is
NUL-terminated before parsing.

Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Arvind Sankar <nivedita@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20200813185811.554051-4-nivedita@xxxxxxxxxxxx
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
 drivers/firmware/efi/libstub/efi-stub-helper.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index f53652a..f735db5 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -194,12 +194,14 @@ efi_status_t efi_parse_options(char const *cmdline)
 	if (!cmdline)
 		return EFI_SUCCESS;
 
-	len = strlen(cmdline) + 1;
+	len = strnlen(cmdline, COMMAND_LINE_SIZE - 1) + 1;
 	status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, len, (void **)&buf);
 	if (status != EFI_SUCCESS)
 		return status;
 
-	str = skip_spaces(memcpy(buf, cmdline, len));
+	memcpy(buf, cmdline, len - 1);
+	buf[len - 1] = '\0';
+	str = skip_spaces(buf);
 
 	while (*str) {
 		char *param, *val;