Re: [PATCH] infiniband: core: fix memory leak

[Leon Romanovsky]

On Sat, Jun 05, 2021 at 11:20:51PM +0300, Pavel Skripkin wrote:
> My local syzbot instance hit memory leak in
> copy_process(). The problem was in unputted task
> struct in _destroy_id().
> 
> Simple reproducer:
> 
> int main(void)
> {
>         struct rdma_ucm_cmd_hdr *hdr;
>         struct rdma_ucm_create_id *cmd_id;
>         char cmd[sizeof(*hdr) + sizeof(*cmd_id)] = {0};
>         int fd;
> 
>         hdr = (struct rdma_ucm_cmd_hdr *)cmd;
>         cmd_id = (struct rdma_ucm_create_id *) (cmd + sizeof(*hdr));
> 
>         hdr->cmd = 0;
>         hdr->in = 0x18;
>         hdr->out = 0xfa00;
> 
>         cmd_id->uid = 0x3;
>         cmd_id->response = 0x0;
>         cmd_id->ps = 0x106;
> 
>         fd = open("/dev/infiniband/rdma_cm", O_WRONLY);
>         write(fd, cmd, sizeof(cmd));
> }
> 
> Ftrace log:
> 
> ucma_open();
> ucma_write() {
>   ucma_create_id() {
>     ucma_alloc_ctx();
>     rdma_create_user_id() {
>       rdma_restrack_new();
>       rdma_restrack_set_name() {
>         rdma_restrack_attach_task.part.0(); <--- task_struct getted
>       }
>     }
>     ucma_destroy_private_ctx() {
>       ucma_put_ctx();
>       rdma_destroy_id() {
>         _destroy_id()			    <--- id_priv freed
>       }
>     }
>   }
> }
> ucma_close();
> 
> From previous log it's easy to undertand that
> _destroy_id() is the last place, where task_struct
> can be putted, because at the end of this function
> id_priv is freed.
> 
> With this patch applied, above reproducer doesn't hit memory
> leak anymore.
> 
> Fixes: e51060f08a61 ("IB: IP address based RDMA connection manager")
> Cc: <stable@xxxxxxxxxxxxxxx>
> Signed-off-by: Pavel Skripkin <paskripkin@xxxxxxxxx>
> ---
>  drivers/infiniband/core/cma.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
> index ab148a696c0c..2760352261b3 100644
> --- a/drivers/infiniband/core/cma.c
> +++ b/drivers/infiniband/core/cma.c
> @@ -1874,6 +1874,7 @@ static void _destroy_id(struct rdma_id_private *id_priv,
>  
>  	kfree(id_priv->id.route.path_rec);
>  
> +	rdma_restrack_put(&id_priv->res);

This change will cause to use-after-free

 [ 2478.766905] ------------[ cut here ]------------
 [ 2478.768721] refcount_t: underflow; use-after-free.
 [ 2478.770577] WARNING: CPU: 1 PID: 56454 at lib/refcount.c:28 refcount_warn_saturate+0x17a/0x190
 [ 2478.773787] Modules linked in: bonding ib_umad ip_gre geneve nf_tables ipip tunnel4 ip6_gre gre ib_ipoib rdma_ucm mlx5_ib ib_uverbs mlx5_core ptp pps_core ip6_tunnel tunnel6 openvswitch nsh xt_conntrack xt_MASQUERADE nf_conntrack_netlink nfnetlink rpcrdma xt_addrtype ib_iser libiscsi scsi_transport_iscsi iptable_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 rdma_cm iw_cm br_netfilter ib_cm ib_core overlay fuse [last unloaded: nf_tables]
 [ 2478.783501] CPU: 1 PID: 56454 Comm: python3 Tainted: G        W         5.13.0-rc4_2021_06_05_20_55_37_ #1
 [ 2478.785418] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 [ 2478.787566] RIP: 0010:refcount_warn_saturate+0x17a/0x190
 [ 2478.788612] Code: 08 e8 00 0f 0b e9 10 ff ff ff 48 89 df e8 ee c2 5d ff e9 d4 fe ff ff 48 c7 c7 40 6d a4 83 c6 05 3b f7 6f 02 01 e8 65 08 e8 00 <0f> 0b e9 e9 fe ff ff 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00
 [ 2478.792014] RSP: 0018:ffff8881277f7b90 EFLAGS: 00010282
 [ 2478.793081] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
 [ 2478.794418] RDX: 0000000000000004 RSI: 0000000000000008 RDI: ffffed1024efef64
 [ 2478.795761] RBP: 0000000000000003 R08: 0000000000000001 R09: ffff8882a40bfd47
 [ 2478.797141] R10: ffffed1054817fa8 R11: ffff88812ab60898 R12: 0000000000000000
 [ 2478.798502] R13: dffffc0000000000 R14: dead000000000100 R15: ffff888102099000
 [ 2478.799863] FS:  00007f5a6492a740(0000) GS:ffff8882a4080000(0000) knlGS:0000000000000000
 [ 2478.801538] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 [ 2478.802671] CR2: 00007f5a56e60900 CR3: 00000001aa7d8002 CR4: 0000000000370ea0
 [ 2478.804030] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 [ 2478.805428] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 [ 2478.806802] Call Trace:
 [ 2478.807380]  rdma_restrack_put+0x5b/0x70 [ib_core]
 [ 2478.808397]  _destroy_id+0x41c/0x760 [rdma_cm]
 [ 2478.809342]  ? ucma_close+0x180/0x180 [rdma_ucm]
 [ 2478.810295]  ? ucma_close+0x180/0x180 [rdma_ucm]
 [ 2478.811252]  ucma_destroy_private_ctx+0x7e4/0xa80 [rdma_ucm]
 [ 2478.812371]  ? ucma_destroy_id+0x18e/0x220 [rdma_ucm]
 [ 2478.813422]  ? ucma_query_route+0xd70/0xd70 [rdma_ucm]
 [ 2478.814464]  ? ucma_close+0x180/0x180 [rdma_ucm]
 [ 2478.815400]  ucma_destroy_id+0x196/0x220 [rdma_ucm]
 [ 2478.816366]  ? ucma_close+0x180/0x180 [rdma_ucm]
 [ 2478.817313]  ucma_write+0x1d2/0x2f0 [rdma_ucm]
 [ 2478.818207]  ? ucma_close_id+0x90/0x90 [rdma_ucm]
 [ 2478.819159]  ? __fget_files+0x1e0/0x2f0
 [ 2478.819958]  vfs_write+0x1c9/0x850
 [ 2478.820681]  ksys_write+0x176/0x1d0
 [ 2478.821436]  ? __x64_sys_read+0xb0/0xb0
 [ 2478.822234]  ? lockdep_hardirqs_on_prepare+0x286/0x400
 [ 2478.823256]  ? syscall_enter_from_user_mode+0x1d/0x50
 [ 2478.824247]  do_syscall_64+0x3f/0x80
 [ 2478.825019]  entry_SYSCALL_64_after_hwframe+0x44/0xae
 [ 2478.826015] RIP: 0033:0x7f5a64ecf32f
 [ 2478.826773] Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 19 4b f9 ff 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 31 44 89 c7 48 89 44 24 08 e8 4c 4b f9 ff 48
 [ 2478.830248] RSP: 002b:00007ffe9ea8d730 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
 [ 2478.831779] RAX: ffffffffffffffda RBX: 00007ffe9ea8d764 RCX: 00007f5a64ecf32f
 [ 2478.833166] RDX: 0000000000000018 RSI: 00007ffe9ea8d770 RDI: 000000000000000a
 [ 2478.834529] RBP: 0000563b16f9f620 R08: 0000000000000000 R09: 00007f5a64db6c60
 [ 2478.835897] R10: 0000000000000001 R11: 0000000000000293 R12: 00007f5a574dea60
 [ 2478.837278] R13: 00007f5a64db49e0 R14: 00007f5a64dba840 R15: 00007f5a565c33a0
 [ 2478.838649] irq event stamp: 23055
 [ 2478.839381] hardirqs last  enabled at (23063): [<ffffffff8146354b>] console_unlock+0x5fb/0x8e0
 [ 2478.841098] hardirqs last disabled at (23072): [<ffffffff81463541>] console_unlock+0x5f1/0x8e0
 [ 2478.842805] softirqs last  enabled at (22670): [<ffffffff81346ba6>] __irq_exit_rcu+0x126/0x1b0
 [ 2478.844498] softirqs last disabled at (22665): [<ffffffff81346ba6>] __irq_exit_rcu+0x126/0x1b0
 [ 2478.846230] ---[ end trace f33482f6d20ccf0e ]---

I think that better fix is:
https://lore.kernel.org/linux-rdma/f72e27d5c82cd9beec7670141afa62786836c569.1622956637.git.leonro@xxxxxxxxxx/T/#u


>  	put_net(id_priv->id.route.addr.dev_addr.net);
>  	kfree(id_priv);
>  }
> -- 
> 2.31.1
>