[PATCH AUTOSEL 4.14 102/105] gtp: fix Illegal context switch in RCU read-side critical section.

Sasha Levin
2019-07-15T14:35:30Z

From: Taehee Yoo <ap420073@gmail.com>

[ Upstream commit 3f167e1921865b379a9becf03828e7202c7b4917 ]

ipv4_pdp_add() is called in RCU read-side critical section.
So GFP_KERNEL should not be used in the function.
This patch make ipv4_pdp_add() to use GFP_ATOMIC instead of GFP_KERNEL.

Test commands:
gtp-link add gtp1 &
gtp-tunnel add gtp1 v1 100 200 1.1.1.1 2.2.2.2

Splat looks like:
[ 130.618881] =============================
[ 130.626382] WARNING: suspicious RCU usage
[ 130.626994] 5.2.0-rc6+ #50 Not tainted
[ 130.627622] -----------------------------
[ 130.628223] ./include/linux/rcupdate.h:266 Illegal context switch in RCU read-side critical section!
[ 130.629684]
[ 130.629684] other info that might help us debug this:
[ 130.629684]
[ 130.631022]
[ 130.631022] rcu_scheduler_active = 2, debug_locks = 1
[ 130.632136] 4 locks held by gtp-tunnel/1025:
[ 130.632925] #0: 000000002b93c8b7 (cb_lock){++++}, at: genl_rcv+0x15/0x40
[ 130.634159] #1: 00000000f17bc999 (genl_mutex){+.+.}, at: genl_rcv_msg+0xfb/0x130
[ 130.635487] #2: 00000000c644ed8e (rtnl_mutex){+.+.}, at: gtp_genl_new_pdp+0x18c/0x1150 [gtp]
[ 130.636936] #3: 0000000007a1cde7 (rcu_read_lock){....}, at: gtp_genl_new_pdp+0x187/0x1150 [gtp]
[ 130.638348]
[ 130.638348] stack backtrace:
[ 130.639062] CPU: 1 PID: 1025 Comm: gtp-tunnel Not tainted 5.2.0-rc6+ #50
[ 130.641318] Call Trace:
[ 130.641707] dump_stack+0x7c/0xbb
[ 130.642252] ___might_sleep+0x2c0/0x3b0
[ 130.642862] kmem_cache_alloc_trace+0x1cd/0x2b0
[ 130.643591] gtp_genl_new_pdp+0x6c5/0x1150 [gtp]
[ 130.644371] genl_family_rcv_msg+0x63a/0x1030
[ 130.645074] ? mutex_lock_io_nested+0x1090/0x1090
[ 130.645845] ? genl_unregister_family+0x630/0x630
[ 130.646592] ? debug_show_all_locks+0x2d0/0x2d0
[ 130.647293] ? check_flags.part.40+0x440/0x440
[ 130.648099] genl_rcv_msg+0xa3/0x130
[ ... ]

Fixes: 459aa660eb1d ("gtp: add initial driver for datapath of GPRS Tunneling Protocol (GTP-U)")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/gtp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
index 2756edd84abc..c751f87c935e 100644
--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -956,7 +956,7 @@ static int ipv4_pdp_add(struct gtp_dev *gtp, struct sock *sk,

}

- pctx = kmalloc(sizeof(struct pdp_ctx), GFP_KERNEL);
+ pctx = kmalloc(sizeof(*pctx), GFP_ATOMIC);
if (pctx == NULL)
return -ENOMEM;

--
2.20.1