[PATCH net-next 09/10] net/smc: fix potential panic dues to unprotected smc_llc_srv_add_link()

D. Wythe
2022-08-10T17:48:10Z

From: "D. Wythe" <alibuda@linux.alibaba.com>

After we optimize the parallel capability of SMC-R connection
establishment, there is a certain chance to trigger the
following panic:

PID: 5900 TASK: ffff88c1c8af4100 CPU: 1 COMMAND: "kworker/1:48"
#0 [ffff9456c1cc79a0] machine_kexec at ffffffff870665b7
#1 [ffff9456c1cc79f0] __crash_kexec at ffffffff871b4c7a
#2 [ffff9456c1cc7ab0] crash_kexec at ffffffff871b5b60
#3 [ffff9456c1cc7ac0] oops_end at ffffffff87026ce7
#4 [ffff9456c1cc7ae0] page_fault_oops at ffffffff87075715
#5 [ffff9456c1cc7b58] exc_page_fault at ffffffff87ad0654
#6 [ffff9456c1cc7b80] asm_exc_page_fault at ffffffff87c00b62
[exception RIP: ib_alloc_mr+19]
RIP: ffffffffc0c9cce3 RSP: ffff9456c1cc7c38 RFLAGS: 00010202
RAX: 0000000000000000 RBX: 0000000000000002 RCX: 0000000000000004
RDX: 0000000000000010 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff88c1ea281d00 R8: 000000020a34ffff R9: ffff88c1350bbb20
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
R13: 0000000000000010 R14: ffff88c1ab040a50 R15: ffff88c1ea281d00
ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
#7 [ffff9456c1cc7c60] smc_ib_get_memory_region at ffffffffc0aff6df [smc]
#8 [ffff9456c1cc7c88] smcr_buf_map_link at ffffffffc0b0278c [smc]
#9 [ffff9456c1cc7ce0] __smc_buf_create at ffffffffc0b03586 [smc]

The reason here is that when the server tries to create a second link,
smc_llc_srv_add_link() has no protection and may add a new link to
link group. This breaks the security environment protected by
llc_conf_mutex.

Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
---
net/smc/af_smc.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 39dbf39..0b0c53a 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1834,8 +1834,10 @@ static int smcr_serv_conf_first_link(struct smc_sock *smc)
smc_llc_link_active(link);
smcr_lgr_set_type(link->lgr, SMC_LGR_SINGLE);

+ down_write(&link->lgr->llc_conf_mutex);
/* initial contact - try to establish second link */
smc_llc_srv_add_link(link, NULL);
+ up_write(&link->lgr->llc_conf_mutex);
return 0;
}

--
1.8.3.1