linux-kernel - [PATCH] efi/libstub: prevent read overflow in find_file

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Message-ID: <YIK0D1JyV6ZeDMSS@mwanda>
Date:   Fri, 23 Apr 2021 14:48:31 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Arvind Sankar <nivedita@...m.mit.edu>,
        Philipp Fent <fent@...tum.de>, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] efi/libstub: prevent read overflow in find_file_option()

If the buffer has slashes up to the end then this will read past the end
of the array.  I don't anticipate that this is an issue for many people
in real life, but it's the right thing to do and it makes static
checkers happy.

Fixes: 7a88a6227dc7 ("efi/libstub: Fix path separator regression")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
 drivers/firmware/efi/libstub/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/libstub/file.c b/drivers/firmware/efi/libstub/file.c
index 4e81c6077188..dd95f330fe6e 100644
--- a/drivers/firmware/efi/libstub/file.c
+++ b/drivers/firmware/efi/libstub/file.c
@@ -103,7 +103,7 @@ static int find_file_option(const efi_char16_t *cmdline, int cmdline_len,
 		return 0;
 
 	/* Skip any leading slashes */
-	while (cmdline[i] == L'/' || cmdline[i] == L'\\')
+	while (i < cmdline_len && (cmdline[i] == L'/' || cmdline[i] == L'\\'))
 		i++;
 
 	while (--result_len > 0 && i < cmdline_len) {
-- 
2.30.2