Re: [Linux-kernel-mentees] [PATCH net] net/smc: Prevent kernel-infoleak in __smc_diag_dump()

[Ursula Braun]

On 8/1/20 9:44 PM, Peilin Ye wrote:
> __smc_diag_dump() is potentially copying uninitialized kernel stack memory
> into socket buffers, since the compiler may leave a 4-byte hole near the
> beginning of `struct smcd_diag_dmbinfo`. Fix it by initializing `dinfo`
> with memset().
> 
> Cc: sta...@vger.kernel.org
> Fixes: 4b1b7d3b30a6 ("net/smc: add SMC-D diag support")
> Suggested-by: Dan Carpenter 
> Signed-off-by: Peilin Ye 
> ---
> Reference: https://lwn.net/Articles/417989/
> 
> $ pahole -C "smcd_diag_dmbinfo" net/smc/smc_diag.o
> struct smcd_diag_dmbinfo {
>   __u32  linkid;   /* 0 4 */
> 
>   /* XXX 4 bytes hole, try to pack */
> 
>   __u64  peer_gid __attribute__((__aligned__(8))); /* 
> 8 8 */
>   __u64  my_gid __attribute__((__aligned__(8))); /*   
>  16 8 */
>   __u64  token __attribute__((__aligned__(8))); /*
> 24 8 */
>   __u64  peer_token __attribute__((__aligned__(8))); 
> /*32 8 */
> 
>   /* size: 40, cachelines: 1, members: 5 */
>   /* sum members: 36, holes: 1, sum holes: 4 */
>   /* forced alignments: 4, forced holes: 1, sum forced holes: 4 */
>   /* last cacheline: 40 bytes */
> } __attribute__((__aligned__(8)));
> $ _
> 

Thanks, patch is added to our local library and will be part of our
next shipment of smc patches for the net-tree.

Regards, Ursula

>  net/smc/smc_diag.c | 16 +---
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/net/smc/smc_diag.c b/net/smc/smc_diag.c
> index e1f64f4ba236..da9ba6d1679b 100644
> --- a/net/smc/smc_diag.c
> +++ b/net/smc/smc_diag.c
> @@ -170,13 +170,15 @@ static int __smc_diag_dump(struct sock *sk, struct 
> sk_buff *skb,
>   (req->diag_ext & (1 << (SMC_DIAG_DMBINFO - 1))) &&
>   !list_empty(>conn.lgr->list)) {
>   struct smc_connection *conn = >conn;
> - struct smcd_diag_dmbinfo dinfo = {
> - .linkid = *((u32 *)conn->lgr->id),
> - .peer_gid = conn->lgr->peer_gid,
> - .my_gid = conn->lgr->smcd->local_gid,
> - .token = conn->rmb_desc->token,
> - .peer_token = conn->peer_token
> - };
> + struct smcd_diag_dmbinfo dinfo;
> +
> + memset(, 0, sizeof(dinfo));
> +
> + dinfo.linkid = *((u32 *)conn->lgr->id);
> + dinfo.peer_gid = conn->lgr->peer_gid;
> + dinfo.my_gid = conn->lgr->smcd->local_gid;
> + dinfo.token = conn->rmb_desc->token;
> + dinfo.peer_token = conn->peer_token;
>  
>   if (nla_put(skb, SMC_DIAG_DMBINFO, sizeof(dinfo), ) < 0)
>   goto errout;
> 

[Linux-kernel-mentees] [PATCH net] net/smc: Prevent kernel-infoleak in __smc_diag_dump()

[Peilin Ye]

__smc_diag_dump() is potentially copying uninitialized kernel stack memory
into socket buffers, since the compiler may leave a 4-byte hole near the
beginning of `struct smcd_diag_dmbinfo`. Fix it by initializing `dinfo`
with memset().

Cc: sta...@vger.kernel.org
Fixes: 4b1b7d3b30a6 ("net/smc: add SMC-D diag support")
Suggested-by: Dan Carpenter 
Signed-off-by: Peilin Ye 
---
Reference: https://lwn.net/Articles/417989/

$ pahole -C "smcd_diag_dmbinfo" net/smc/smc_diag.o
struct smcd_diag_dmbinfo {
__u32  linkid;   /* 0 4 */

/* XXX 4 bytes hole, try to pack */

__u64  peer_gid __attribute__((__aligned__(8))); /* 
8 8 */
__u64  my_gid __attribute__((__aligned__(8))); /*   
 16 8 */
__u64  token __attribute__((__aligned__(8))); /*
24 8 */
__u64  peer_token __attribute__((__aligned__(8))); 
/*32 8 */

/* size: 40, cachelines: 1, members: 5 */
/* sum members: 36, holes: 1, sum holes: 4 */
/* forced alignments: 4, forced holes: 1, sum forced holes: 4 */
/* last cacheline: 40 bytes */
} __attribute__((__aligned__(8)));
$ _

 net/smc/smc_diag.c | 16 +---
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/net/smc/smc_diag.c b/net/smc/smc_diag.c
index e1f64f4ba236..da9ba6d1679b 100644
--- a/net/smc/smc_diag.c
+++ b/net/smc/smc_diag.c
@@ -170,13 +170,15 @@ static int __smc_diag_dump(struct sock *sk, struct 
sk_buff *skb,
(req->diag_ext & (1 << (SMC_DIAG_DMBINFO - 1))) &&
!list_empty(>conn.lgr->list)) {
struct smc_connection *conn = >conn;
-   struct smcd_diag_dmbinfo dinfo = {
-   .linkid = *((u32 *)conn->lgr->id),
-   .peer_gid = conn->lgr->peer_gid,
-   .my_gid = conn->lgr->smcd->local_gid,
-   .token = conn->rmb_desc->token,
-   .peer_token = conn->peer_token
-   };
+   struct smcd_diag_dmbinfo dinfo;
+
+   memset(, 0, sizeof(dinfo));
+
+   dinfo.linkid = *((u32 *)conn->lgr->id);
+   dinfo.peer_gid = conn->lgr->peer_gid;
+   dinfo.my_gid = conn->lgr->smcd->local_gid;
+   dinfo.token = conn->rmb_desc->token;
+   dinfo.peer_token = conn->peer_token;
 
if (nla_put(skb, SMC_DIAG_DMBINFO, sizeof(dinfo), ) < 0)
goto errout;
-- 
2.25.1