linux-kernel - [PATCH v3 13/21] x86/kaslr: Drop test for command-line parameters before parsing

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Date:   Tue, 28 Jul 2020 18:57:14 -0400
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Kees Cook <keescook@...omium.org>, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH v3 13/21] x86/kaslr: Drop test for command-line parameters before parsing

This check doesn't save anything. In the case when none of the
parameters are present, each strstr will scan args twice (once to find
the length and then for searching), six scans in total. Just going ahead
and parsing the arguments only requires three scans: strlen, memcpy, and
parsing. This will be the first malloc, so free will actually free up
the memory, so the check doesn't save heap space either.

Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu>
---
 arch/x86/boot/compressed/kaslr.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 7fb699aae74e..7c69fc10a782 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -279,10 +279,6 @@ static void handle_mem_options(void)
 	if (!args)
 		return;

-	if (!strstr(args, "memmap=") && !strstr(args, "mem=") &&
-		!strstr(args, "hugepages"))
-		return;
-
 	len = strlen(args);
 	tmp_cmdline = malloc(len + 1);
 	if (!tmp_cmdline)
-- 
2.26.2