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Subject[PATCH 06/16] drbd: Wrong use of RCU in receive_protocol()
Date
From: Andreas Gruenbacher <agruen@linbit.com>

It is not enough to grab net_conf->integrity_alg under rcu_read_lock()
and access it outside of it; the entire net_conf object may be gone by
then.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
---
drivers/block/drbd/drbd_receiver.c | 32 +++++++++++++++++++-------------
1 files changed, 19 insertions(+), 13 deletions(-)
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 6da7aeb..98f03b1 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -2998,7 +2998,6 @@ static int receive_protocol(struct drbd_tconn *tconn, struct packet_info *pi)
int p_proto, p_after_sb_0p, p_after_sb_1p, p_after_sb_2p;
int p_want_lose, p_two_primaries, cf;
char p_integrity_alg[SHARED_SECRET_MAX] = "";
- unsigned char *my_alg;
struct net_conf *nc;

p_proto = be32_to_cpu(p->protocol);
@@ -3009,6 +3008,18 @@ static int receive_protocol(struct drbd_tconn *tconn, struct packet_info *pi)
cf = be32_to_cpu(p->conn_flags);
p_want_lose = cf & CF_WANT_LOSE;

+ if (tconn->agreed_pro_version >= 87) {
+ int err;
+
+ if (pi->size > sizeof(p_integrity_alg))
+ return -EIO;
+ err = drbd_recv_all(tconn, p_integrity_alg, pi->size);
+ if (err)
+ return err;
+
+ p_integrity_alg[SHARED_SECRET_MAX-1] = 0;
+ }
+
clear_bit(CONN_DRY_RUN, &tconn->flags);

if (cf & CF_DRY_RUN)
@@ -3047,23 +3058,18 @@ static int receive_protocol(struct drbd_tconn *tconn, struct packet_info *pi)
goto disconnect_rcu_unlock;
}

- my_alg = nc->integrity_alg;
- rcu_read_unlock();
-
if (tconn->agreed_pro_version >= 87) {
- int err;
-
- err = drbd_recv_all(tconn, p_integrity_alg, pi->size);
- if (err)
- return err;
-
- p_integrity_alg[SHARED_SECRET_MAX-1] = 0;
- if (strcmp(p_integrity_alg, my_alg)) {
+ if (strcmp(p_integrity_alg, nc->integrity_alg)) {
conn_err(tconn, "incompatible setting of the data-integrity-alg\n");
goto disconnect;
}
+ }
+
+ rcu_read_unlock();
+
+ if (tconn->agreed_pro_version >= 87) {
conn_info(tconn, "data-integrity-alg: %s\n",
- my_alg[0] ? my_alg : (unsigned char *)"<not-used>");
+ nc->integrity_alg[0] ? nc->integrity_alg : (unsigned char *)"<not-used>");
}

return 0;
--
1.7.4.1


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