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Subject[Linux-kernel-mentees] [PATCH net] net/smc: Prevent kernel-infoleak in __smc_diag_dump()
Date
__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: stable@vger.kernel.org
Fixes: 4b1b7d3b30a6 ("net/smc: add SMC-D diag support")
Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
---
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(&smc->conn.lgr->list)) {
struct smc_connection *conn = &smc->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(&dinfo, 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), &dinfo) < 0)
goto errout;
--
2.25.1
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