On Thu, Jun 01, 2023 at 04:41:52PM +0800, Wen Gu wrote:
> SMCRv1 has a similar issue to SMCRv2 (see link below) that may access
> invalid MRs of RMBs when construct LLC ADD LINK CONT messages.
>
> BUG: kernel NULL pointer dereference, address: 0000000000000014
> #PF: supervisor read access in kernel mode
> #PF: error_code(0x0000) - not-present page
> PGD 0 P4D 0
> Oops: 0000 [#1] PREEMPT SMP PTI
> CPU: 5 PID: 48 Comm: kworker/5:0 Kdump: loaded Tainted: G W E 6.4.0-rc3+ #49
> Workqueue: events smc_llc_add_link_work [smc]
> RIP: 0010:smc_llc_add_link_cont+0x160/0x270 [smc]
> RSP: 0018:ffffa737801d3d50 EFLAGS: 00010286
> RAX: ffff964f82144000 RBX: ffffa737801d3dd8 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff964f81370c30
> RBP: ffffa737801d3dd4 R08: ffff964f81370000 R09: ffffa737801d3db0
> R10: 0000000000000001 R11: 0000000000000060 R12: ffff964f82e70000
> R13: ffff964f81370c38 R14: ffffa737801d3dd3 R15: 0000000000000001
> FS: 0000000000000000(0000) GS:ffff9652bfd40000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000014 CR3: 000000008fa20004 CR4: 00000000003706e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> smc_llc_srv_rkey_exchange+0xa7/0x190 [smc]
> smc_llc_srv_add_link+0x3ae/0x5a0 [smc]
> smc_llc_add_link_work+0xb8/0x140 [smc]
> process_one_work+0x1e5/0x3f0
> worker_thread+0x4d/0x2f0
> ? __pfx_worker_thread+0x10/0x10
> kthread+0xe5/0x120
> ? __pfx_kthread+0x10/0x10
> ret_from_fork+0x2c/0x50
> </TASK>
>
> When an alernate RNIC is available in system, SMC will try to add a new
> link based on the RNIC for resilience. All the RMBs in use will be mapped
> to the new link. Then the RMBs' MRs corresponding to the new link will
> be filled into LLC messages. For SMCRv1, they are ADD LINK CONT messages.
>
> However smc_llc_add_link_cont() may mistakenly access to unused RMBs which
> haven't been mapped to the new link and have no valid MRs, thus causing a
> crash. So this patch fixes it.
>
> Fixes: 87f88cda2128 ("net/smc: rkey processing for a new link as SMC client")
> Link: https://lore.kernel.org/r/1685101741-74826-3-git-send-email-guwen@xxxxxxxxxxxxxxxxx
> Signed-off-by: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
This SGTM, thanks.
Reviewed-by: Tony Lu <tonylu@xxxxxxxxxxxxxxxxx>
> ---
> net/smc/smc_llc.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/smc/smc_llc.c b/net/smc/smc_llc.c
> index 7a8d916..90f0b60 100644
> --- a/net/smc/smc_llc.c
> +++ b/net/smc/smc_llc.c
> @@ -851,6 +851,8 @@ static int smc_llc_add_link_cont(struct smc_link *link,
> addc_llc->num_rkeys = *num_rkeys_todo;
> n = *num_rkeys_todo;
> for (i = 0; i < min_t(u8, n, SMC_LLC_RKEYS_PER_CONT_MSG); i++) {
> + while (*buf_pos && !(*buf_pos)->used)
> + *buf_pos = smc_llc_get_next_rmb(lgr, buf_lst, *buf_pos);
> if (!*buf_pos) {
> addc_llc->num_rkeys = addc_llc->num_rkeys -
> *num_rkeys_todo;
> @@ -867,8 +869,6 @@ static int smc_llc_add_link_cont(struct smc_link *link,
>
> (*num_rkeys_todo)--;
> *buf_pos = smc_llc_get_next_rmb(lgr, buf_lst, *buf_pos);
> - while (*buf_pos && !(*buf_pos)->used)
> - *buf_pos = smc_llc_get_next_rmb(lgr, buf_lst, *buf_pos);
> }
> addc_llc->hd.common.llc_type = SMC_LLC_ADD_LINK_CONT;
> addc_llc->hd.length = sizeof(struct smc_llc_msg_add_link_cont);
> --
> 1.8.3.1
