[Linux-kernel-mentees] [PATCH net v2] xdp: Prevent kernel-infoleak in xsk_getsockopt()

Peilin Ye yepeilin.cs at gmail.com
Tue Jul 28 05:36:04 UTC 2020

xsk_getsockopt() is copying uninitialized stack memory to userspace when
`extra_stats` is `false`. Fix it.

Fixes: 8aa5a33578e9 ("xsk: Add new statistics")
Suggested-by: Dan Carpenter <dan.carpenter at oracle.com>
Signed-off-by: Peilin Ye <yepeilin.cs at gmail.com>
Doing `= {};` is sufficient since currently `struct xdp_statistics` is
defined as follows:

struct xdp_statistics {
	__u64 rx_dropped;
	__u64 rx_invalid_descs;
	__u64 tx_invalid_descs;
	__u64 rx_ring_full;
	__u64 rx_fill_ring_empty_descs;
	__u64 tx_ring_empty_descs;

When being copied to the userspace, `stats` will not contain any
uninitialized "holes" between struct fields.

Changes in v2:
    - Remove the "Cc: stable at vger.kernel.org" tag. (Suggested by Song Liu
      <songliubraving at fb.com>)
    - Initialize `stats` by assignment instead of using memset().
      (Suggested by Song Liu <songliubraving at fb.com>)

 net/xdp/xsk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 26e3bba8c204..b2b533eddebf 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -840,7 +840,7 @@ static int xsk_getsockopt(struct socket *sock, int level, int optname,
 	switch (optname) {
-		struct xdp_statistics stats;
+		struct xdp_statistics stats = {};
 		bool extra_stats = true;
 		size_t stats_size;

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