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SubjectRe: [PATCH v2] drivers/net/cxgb3/cxgb3_main.c: prevent reading uninitialized stack memory
On Wed, Sep 15, 2010 at 05:43:12PM -0400, Dan Rosenberg wrote:
> Fixed formatting (tabs and line breaks).
>
> The CHELSIO_GET_QSET_NUM device ioctl allows unprivileged users to read
> 4 bytes of uninitialized stack memory, because the "addr" member of the
> ch_reg struct declared on the stack in cxgb_extension_ioctl() is not
> altered or zeroed before being copied back to the user. This patch
> takes care of it.
>
> Signed-off-by: Dan Rosenberg <dan.j.rosenberg@gmail.com>
>
> --- linux-2.6.35.4.orig/drivers/net/cxgb3/cxgb3_main.c 2010-08-26 19:47:12.000000000 -0400
> +++ linux-2.6.35.4/drivers/net/cxgb3/cxgb3_main.c 2010-09-14 21:24:34.369511115 -0400
> @@ -2296,6 +2296,8 @@ static int cxgb_extension_ioctl(struct n
> case CHELSIO_GET_QSET_NUM:{
> struct ch_reg edata;
>
> + memset(&edata, 0, sizeof(struct ch_reg));
> +
> edata.cmd = CHELSIO_GET_QSET_NUM;
> edata.val = pi->nqsets;

This is a pretty expensive way to fix it. either...

+ edata.addr = 0;

or:

- struct ch_reg edata;
+ struct ch_reg edata = {
+ .cmd = CHELSIO_GET_QSET_NUM,
+ .val = pi->nqsets
+ };

- edata.cmd = CHELSIO_GET_QSET_NUM;
- edata.val = pi->nqsets;

If you are worried that the struct ch_reg may grow someday.

-- Steve

> if (copy_to_user(useraddr, &edata, sizeof(edata)))
>
>


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