On Fri, Jun 14, 2024 at 08:30:44PM +0300, Dan Carpenter wrote:
> There are actually two bugs here. First, we need to ensure that count
> is at least sizeof(u32) or msg.len will be uninitialized data.
>
> The "msg.len" variable is a u32 that comes from the user. On 32bit
> systems the "sizeof_field(struct ipmi_ssif_msg, len) + msg.len"
> addition can overflow if "msg.len" is greater than U32_MAX - 4.
>
> Valid lengths for "msg.len" are 1-254. Add a check for that to
> prevent the integer overflow.
Thanks, this is in my tree.
-corey
>
> Fixes: dd2bc5cc9e25 ("ipmi: ssif_bmc: Add SSIF BMC driver")
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> ---
> drivers/char/ipmi/ssif_bmc.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
> ---
> drivers/char/ipmi/ssif_bmc.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/char/ipmi/ssif_bmc.c b/drivers/char/ipmi/ssif_bmc.c
> index 56346fb32872..ab4e87a99f08 100644
> --- a/drivers/char/ipmi/ssif_bmc.c
> +++ b/drivers/char/ipmi/ssif_bmc.c
> @@ -177,13 +177,15 @@ static ssize_t ssif_bmc_write(struct file *file, const char __user *buf, size_t
> unsigned long flags;
> ssize_t ret;
>
> - if (count > sizeof(struct ipmi_ssif_msg))
> + if (count < sizeof(msg.len) ||
> + count > sizeof(struct ipmi_ssif_msg))
> return -EINVAL;
>
> if (copy_from_user(&msg, buf, count))
> return -EFAULT;
>
> - if (!msg.len || count < sizeof_field(struct ipmi_ssif_msg, len) + msg.len)
> + if (!msg.len || msg.len > IPMI_SSIF_PAYLOAD_MAX ||
> + count < sizeof_field(struct ipmi_ssif_msg, len) + msg.len)
> return -EINVAL;
>
> spin_lock_irqsave(&ssif_bmc->lock, flags);
> --
> 2.43.0
>
