netdev - [PATCH net 1/2] ptp: check that rsv field is zero in struct ptp_sys_offset

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Message-ID: <20190107152229.GA17925@asgard.redhat.com>
Date:   Mon, 7 Jan 2019 16:22:29 +0100
From:   Eugene Syromiatnikov <esyr@...hat.com>
To:     Miroslav Lichvar <mlichvar@...hat.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Cc:     Richard Cochran <richardcochran@...il.com>,
        Jacob Keller <jacob.e.keller@...el.com>,
        Marcelo Tosatti <mtosatti@...hat.com>
Subject: [PATCH net 1/2] ptp: check that rsv field is zero in struct
 ptp_sys_offset_extended

Otherwise it is impossible to use it for something else, as it will break
userspace that puts garbage there.

The same check should be done in other structures, but the fact that
data in reserved fields is ignored is already part of the kernel ABI.

Signed-off-by: Eugene Syromiatnikov <esyr@...hat.com>
---
 drivers/ptp/ptp_chardev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index 797fab3..7cbea79 100644
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -224,7 +224,8 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
 			extoff = NULL;
 			break;
 		}
-		if (extoff->n_samples > PTP_MAX_SAMPLES) {
+		if (extoff->n_samples > PTP_MAX_SAMPLES
+		    || extoff->rsv[0] || extoff->rsv[1] || extoff->rsv[2]) {
 			err = -EINVAL;
 			break;
 		}
-- 
2.1.4