2021-04-23 11:51:29

by Dan Carpenter

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 <[email protected]>
---
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

2021-05-10 15:40:53

by Ard Biesheuvel

Subject: Re: [PATCH] efi/libstub: prevent read overflow in find_file_option()

On Fri, 23 Apr 2021 at 13:48, Dan Carpenter <[email protected]> wrote:
>
> 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 <[email protected]>
> ---
> 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
>

Thanks Dan, I will queue this up.