2021-07-14 12:16:34

by Yi Zhuang

Subject: [PATCH v2] powerpc/rtas_flash: fix a potential buffer overflow

Since snprintf() returns the possible output size instead of the
actual output size, the available flash_msg length returned by
get_validate_flash_msg may exceed the given buffer limit when
simple_read_from_buffer calls copy_to_user

Reported-by: kernel test robot <[email protected]>
Fixes: a94a14720eaf5 powerpc/rtas_flash: Fix validate_flash buffer overflow issue
Signed-off-by: Yi Zhuang <[email protected]>
---
arch/powerpc/kernel/rtas_flash.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/rtas_flash.c b/arch/powerpc/kernel/rtas_flash.c
index a99179d83538..062f0724c2ff 100644
--- a/arch/powerpc/kernel/rtas_flash.c
+++ b/arch/powerpc/kernel/rtas_flash.c
@@ -470,9 +470,14 @@ static int get_validate_flash_msg(struct rtas_validate_flash_t *args_buf,
if (args_buf->status >= VALIDATE_TMP_UPDATE) {
n = sprintf(msg, "%d\n", args_buf->update_results);
if ((args_buf->update_results >= VALIDATE_CUR_UNKNOWN) ||
- (args_buf->update_results == VALIDATE_TMP_UPDATE))
+ (args_buf->update_results == VALIDATE_TMP_UPDATE)) {
n += snprintf(msg + n, msglen - n, "%s\n",
args_buf->buf);
+ if (n >= msglen) {
+ n = msglen;
+ printk(KERN_ERR "FLASH: msg too long.\n");
+ }
+ }
} else {
n = sprintf(msg, "%d\n", args_buf->status);
}
--
2.26.0.106.g9fadedd

2021-07-14 16:49:20

by Christophe Leroy

Subject: Re: [PATCH v2] powerpc/rtas_flash: fix a potential buffer overflow

Yi Zhuang <[email protected]> a écrit :

> Since snprintf() returns the possible output size instead of the
> actual output size, the available flash_msg length returned by
> get_validate_flash_msg may exceed the given buffer limit when
> simple_read_from_buffer calls copy_to_user
>
> Reported-by: kernel test robot <[email protected]>
> Fixes: a94a14720eaf5 powerpc/rtas_flash: Fix validate_flash buffer
> overflow issue
> Signed-off-by: Yi Zhuang <[email protected]>
> ---
> arch/powerpc/kernel/rtas_flash.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kernel/rtas_flash.c
> b/arch/powerpc/kernel/rtas_flash.c
> index a99179d83538..062f0724c2ff 100644
> --- a/arch/powerpc/kernel/rtas_flash.c
> +++ b/arch/powerpc/kernel/rtas_flash.c
> @@ -470,9 +470,14 @@ static int get_validate_flash_msg(struct
> rtas_validate_flash_t *args_buf,
> if (args_buf->status >= VALIDATE_TMP_UPDATE) {
> n = sprintf(msg, "%d\n", args_buf->update_results);
> if ((args_buf->update_results >= VALIDATE_CUR_UNKNOWN) ||
> - (args_buf->update_results == VALIDATE_TMP_UPDATE))
> + (args_buf->update_results == VALIDATE_TMP_UPDATE)) {
> n += snprintf(msg + n, msglen - n, "%s\n",
> args_buf->buf);
> + if (n >= msglen) {

n cannot be greater than msglen


> + n = msglen;
> + printk(KERN_ERR "FLASH: msg too long.\n");
> + }
> + }
> } else {
> n = sprintf(msg, "%d\n", args_buf->status);
> }
> --
> 2.26.0.106.g9fadedd