[PATCH 5.12 009/161] efi/libstub: prevent read overflow in find_file_option()

[Greg Kroah-Hartman]

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

[ Upstream commit c4039b29fe9637e1135912813f830994af4c867f ]

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@xxxxxxxxxx>
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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