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authorJiri Pirko <jiri@nvidia.com>2024-02-07 12:59:02 +0100
committerJakub Kicinski <kuba@kernel.org>2024-02-08 18:29:21 -0800
commit53c0441dd2c44ee93fddb5473885fd41e4bc2361 (patch)
tree3ff6fdf50fa8e8faefb61fdc1999f6d135cd40c8
parent1f719a2f3fa67665578c759ac34fd3d3690c1a20 (diff)
dpll: fix possible deadlock during netlink dump operation
Recently, I've been hitting following deadlock warning during dpll pin dump: [52804.637962] ====================================================== [52804.638536] WARNING: possible circular locking dependency detected [52804.639111] 6.8.0-rc2jiri+ #1 Not tainted [52804.639529] ------------------------------------------------------ [52804.640104] python3/2984 is trying to acquire lock: [52804.640581] ffff88810e642678 (nlk_cb_mutex-GENERIC){+.+.}-{3:3}, at: netlink_dump+0xb3/0x780 [52804.641417] but task is already holding lock: [52804.642010] ffffffff83bde4c8 (dpll_lock){+.+.}-{3:3}, at: dpll_lock_dumpit+0x13/0x20 [52804.642747] which lock already depends on the new lock. [52804.643551] the existing dependency chain (in reverse order) is: [52804.644259] -> #1 (dpll_lock){+.+.}-{3:3}: [52804.644836] lock_acquire+0x174/0x3e0 [52804.645271] __mutex_lock+0x119/0x1150 [52804.645723] dpll_lock_dumpit+0x13/0x20 [52804.646169] genl_start+0x266/0x320 [52804.646578] __netlink_dump_start+0x321/0x450 [52804.647056] genl_family_rcv_msg_dumpit+0x155/0x1e0 [52804.647575] genl_rcv_msg+0x1ed/0x3b0 [52804.648001] netlink_rcv_skb+0xdc/0x210 [52804.648440] genl_rcv+0x24/0x40 [52804.648831] netlink_unicast+0x2f1/0x490 [52804.649290] netlink_sendmsg+0x36d/0x660 [52804.649742] __sock_sendmsg+0x73/0xc0 [52804.650165] __sys_sendto+0x184/0x210 [52804.650597] __x64_sys_sendto+0x72/0x80 [52804.651045] do_syscall_64+0x6f/0x140 [52804.651474] entry_SYSCALL_64_after_hwframe+0x46/0x4e [52804.652001] -> #0 (nlk_cb_mutex-GENERIC){+.+.}-{3:3}: [52804.652650] check_prev_add+0x1ae/0x1280 [52804.653107] __lock_acquire+0x1ed3/0x29a0 [52804.653559] lock_acquire+0x174/0x3e0 [52804.653984] __mutex_lock+0x119/0x1150 [52804.654423] netlink_dump+0xb3/0x780 [52804.654845] __netlink_dump_start+0x389/0x450 [52804.655321] genl_family_rcv_msg_dumpit+0x155/0x1e0 [52804.655842] genl_rcv_msg+0x1ed/0x3b0 [52804.656272] netlink_rcv_skb+0xdc/0x210 [52804.656721] genl_rcv+0x24/0x40 [52804.657119] netlink_unicast+0x2f1/0x490 [52804.657570] netlink_sendmsg+0x36d/0x660 [52804.658022] __sock_sendmsg+0x73/0xc0 [52804.658450] __sys_sendto+0x184/0x210 [52804.658877] __x64_sys_sendto+0x72/0x80 [52804.659322] do_syscall_64+0x6f/0x140 [52804.659752] entry_SYSCALL_64_after_hwframe+0x46/0x4e [52804.660281] other info that might help us debug this: [52804.661077] Possible unsafe locking scenario: [52804.661671] CPU0 CPU1 [52804.662129] ---- ---- [52804.662577] lock(dpll_lock); [52804.662924] lock(nlk_cb_mutex-GENERIC); [52804.663538] lock(dpll_lock); [52804.664073] lock(nlk_cb_mutex-GENERIC); [52804.664490] The issue as follows: __netlink_dump_start() calls control->start(cb) with nlk->cb_mutex held. In control->start(cb) the dpll_lock is taken. Then nlk->cb_mutex is released and taken again in netlink_dump(), while dpll_lock still being held. That leads to ABBA deadlock when another CPU races with the same operation. Fix this by moving dpll_lock taking into dumpit() callback which ensures correct lock taking order. Fixes: 9d71b54b65b1 ("dpll: netlink: Add DPLL framework base functions") Signed-off-by: Jiri Pirko <jiri@nvidia.com> Reviewed-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com> Link: https://lore.kernel.org/r/20240207115902.371649-1-jiri@resnulli.us Signed-off-by: Jakub Kicinski <kuba@kernel.org>
-rw-r--r--Documentation/netlink/specs/dpll.yaml4
-rw-r--r--drivers/dpll/dpll_netlink.c20
-rw-r--r--drivers/dpll/dpll_nl.c4
-rw-r--r--drivers/dpll/dpll_nl.h2
4 files changed, 6 insertions, 24 deletions
diff --git a/Documentation/netlink/specs/dpll.yaml b/Documentation/netlink/specs/dpll.yaml
index b14aed18065f..3dcc9ece272a 100644
--- a/Documentation/netlink/specs/dpll.yaml
+++ b/Documentation/netlink/specs/dpll.yaml
@@ -384,8 +384,6 @@ operations:
- type
dump:
- pre: dpll-lock-dumpit
- post: dpll-unlock-dumpit
reply: *dev-attrs
-
@@ -473,8 +471,6 @@ operations:
- fractional-frequency-offset
dump:
- pre: dpll-lock-dumpit
- post: dpll-unlock-dumpit
request:
attributes:
- id
diff --git a/drivers/dpll/dpll_netlink.c b/drivers/dpll/dpll_netlink.c
index 314bb3775465..4ca9ad16cd95 100644
--- a/drivers/dpll/dpll_netlink.c
+++ b/drivers/dpll/dpll_netlink.c
@@ -1199,6 +1199,7 @@ int dpll_nl_pin_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
unsigned long i;
int ret = 0;
+ mutex_lock(&dpll_lock);
xa_for_each_marked_start(&dpll_pin_xa, i, pin, DPLL_REGISTERED,
ctx->idx) {
if (!dpll_pin_available(pin))
@@ -1218,6 +1219,8 @@ int dpll_nl_pin_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
}
genlmsg_end(skb, hdr);
}
+ mutex_unlock(&dpll_lock);
+
if (ret == -EMSGSIZE) {
ctx->idx = i;
return skb->len;
@@ -1373,6 +1376,7 @@ int dpll_nl_device_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
unsigned long i;
int ret = 0;
+ mutex_lock(&dpll_lock);
xa_for_each_marked_start(&dpll_device_xa, i, dpll, DPLL_REGISTERED,
ctx->idx) {
hdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid,
@@ -1389,6 +1393,8 @@ int dpll_nl_device_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
}
genlmsg_end(skb, hdr);
}
+ mutex_unlock(&dpll_lock);
+
if (ret == -EMSGSIZE) {
ctx->idx = i;
return skb->len;
@@ -1439,20 +1445,6 @@ dpll_unlock_doit(const struct genl_split_ops *ops, struct sk_buff *skb,
mutex_unlock(&dpll_lock);
}
-int dpll_lock_dumpit(struct netlink_callback *cb)
-{
- mutex_lock(&dpll_lock);
-
- return 0;
-}
-
-int dpll_unlock_dumpit(struct netlink_callback *cb)
-{
- mutex_unlock(&dpll_lock);
-
- return 0;
-}
-
int dpll_pin_pre_doit(const struct genl_split_ops *ops, struct sk_buff *skb,
struct genl_info *info)
{
diff --git a/drivers/dpll/dpll_nl.c b/drivers/dpll/dpll_nl.c
index eaee5be7aa64..1e95f5397cfc 100644
--- a/drivers/dpll/dpll_nl.c
+++ b/drivers/dpll/dpll_nl.c
@@ -95,9 +95,7 @@ static const struct genl_split_ops dpll_nl_ops[] = {
},
{
.cmd = DPLL_CMD_DEVICE_GET,
- .start = dpll_lock_dumpit,
.dumpit = dpll_nl_device_get_dumpit,
- .done = dpll_unlock_dumpit,
.flags = GENL_ADMIN_PERM | GENL_CMD_CAP_DUMP,
},
{
@@ -129,9 +127,7 @@ static const struct genl_split_ops dpll_nl_ops[] = {
},
{
.cmd = DPLL_CMD_PIN_GET,
- .start = dpll_lock_dumpit,
.dumpit = dpll_nl_pin_get_dumpit,
- .done = dpll_unlock_dumpit,
.policy = dpll_pin_get_dump_nl_policy,
.maxattr = DPLL_A_PIN_ID,
.flags = GENL_ADMIN_PERM | GENL_CMD_CAP_DUMP,
diff --git a/drivers/dpll/dpll_nl.h b/drivers/dpll/dpll_nl.h
index 92d4c9c4f788..f491262bee4f 100644
--- a/drivers/dpll/dpll_nl.h
+++ b/drivers/dpll/dpll_nl.h
@@ -30,8 +30,6 @@ dpll_post_doit(const struct genl_split_ops *ops, struct sk_buff *skb,
void
dpll_pin_post_doit(const struct genl_split_ops *ops, struct sk_buff *skb,
struct genl_info *info);
-int dpll_lock_dumpit(struct netlink_callback *cb);
-int dpll_unlock_dumpit(struct netlink_callback *cb);
int dpll_nl_device_id_get_doit(struct sk_buff *skb, struct genl_info *info);
int dpll_nl_device_get_doit(struct sk_buff *skb, struct genl_info *info);