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@vger.kernel.org>
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200813185811.554051-4-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index f53652a..f735db5 100644 (file)
--- 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;