Hi,
Le vendredi 28 mars 2014 à 11:24 +0300, Dan Carpenter a écrit :
> The c4iw_alloc_ucontext_resp struct has a 4 byte hole after the last
> member and we should clear it before passing it to the user.
>
> Fixes: 05eb23893c2c ('cxgb4/iw_cxgb4: Doorbell Drop Avoidance Bug Fixes')
> Signed-off-by: Dan Carpenter <[email protected]>
>
It's not the proper fix for this issue: an explicit padding has to be
added (and initialized), see "Re: [PATCH net-next 2/2] cxgb4/iw_cxgb4:
Doorbell Drop Avoidance Bug Fixes"
http://marc.info/[email protected]
In its current form, the c4iw_alloc_ucontext_resp structure does not
require padding on i386, so a 32bits userspace program using this
structure against a x86_64 kernel will make the kernel do a buffer
overflow in userspace, likely on stack, as answer of a GET_CONTEXT
request:
#include <infiniband/verbs.h>
#include <infiniband/kern-abi.h>
#define IBV_INIT_CMD_RESP(cmd, size, opcode, out, outsize) \
do { \
(cmd)->command = IB_USER_VERBS_CMD_##opcode; \
(cmd)->in_words = (size) / 4; \
(cmd)->out_words = (outsize) / 4; \
(cmd)->response = (out); \
} while (0)
struct c4iw_alloc_ucontext_resp {
struct ibv_get_context_resp ibv_resp;
__u64 status_page_key;
__u32 status_page_size;
};
struct ibv_context *alloc_context(struct ibv_device *ibdev,
int cmd_fd)
{
struct ibv_get_context cmd;
struct c4iw_alloc_ucontext_resp resp;
ssize_t sret;
...
IBV_INIT_CMD_RESP(&cmd, sizeof(cmd),
GET_CONTEXT,
&resp, sizeof(resp));
...
sret = write(context->cmd_fd,
&cmd,
sizeof(cmd));
if (sret != sizeof(cmd)) {
int err = errno;
fprintf(stderr, "GET_CONTEXT failed: %d (%s)\n",
err, strerror(err));
...
}
...
}
Unfortunately, it's not the only structure which has this problem. I'm
currently preparing a report on this issue for this driver (cxgb4) and
another.
> diff --git a/drivers/infiniband/hw/cxgb4/provider.c
> b/drivers/infiniband/hw/cxgb4/provider.c
> index e36d2a2..a72aaa7 100644
> --- a/drivers/infiniband/hw/cxgb4/provider.c
> +++ b/drivers/infiniband/hw/cxgb4/provider.c
> @@ -107,7 +107,7 @@ static struct ib_ucontext *c4iw_alloc_ucontext(struct
> ib_device *ibdev,
> struct c4iw_ucontext *context;
> struct c4iw_dev *rhp = to_c4iw_dev(ibdev);
> static int warned;
> - struct c4iw_alloc_ucontext_resp uresp;
> + struct c4iw_alloc_ucontext_resp uresp = {};
> int ret = 0;
> struct c4iw_mm_entry *mm = NULL;
>
Regards.
--
Yann Droneaud
OPTEYA
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