[PATCH rdma-next] RDMA/cm: Update num_paths in cma_resolve_iboe_route error flow

[Leon Romanovsky <leon@kernel.org>]

From: Avihai Horon <avihaih@mellanox.com>

After a successful allocation of path_rec, num_paths is set to 1,
but any error after such allocation will leave num_paths uncleared.

This causes to de-referencing a NULL pointer later on. Hence,
num_paths needs to be set back to 0 if such an error occurs.

The following crash from syzkaller revealed it.

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
CPU: 0 PID: 357 Comm: syz-executor060 Not tainted 4.18.0+ #311
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.11.0-0-g63451fca13-prebuilt.qemu-project.org 04/01/2014
RIP: 0010:ib_copy_path_rec_to_user+0x94/0x3e0
Code: f1 f1 f1 f1 c7 40 0c 00 00 f4 f4 65 48 8b 04 25 28 00 00 00 48 89
45 c8 31 c0 e8 d7 60 24 ff 48 8d 7b 4c 48 89 f8 48 c1 e8 03 <42> 0f b6
14 30 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85
RSP: 0018:ffff88006586f980 EFLAGS: 00010207
RAX: 0000000000000009 RBX: 0000000000000000 RCX: 1ffff1000d5fe475
RDX: ffff8800621e17c0 RSI: ffffffff820d45f9 RDI: 000000000000004c
RBP: ffff88006586fa50 R08: ffffed000cb0df73 R09: ffffed000cb0df72
R10: ffff88006586fa70 R11: ffffed000cb0df73 R12: 1ffff1000cb0df30
R13: ffff88006586fae8 R14: dffffc0000000000 R15: ffff88006aff2200
FS: 00000000016fc880(0000) GS:ffff88006d000000(0000)
knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000040 CR3: 0000000063fec000 CR4: 00000000000006b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
? ib_copy_path_rec_from_user+0xcc0/0xcc0
? __mutex_unlock_slowpath+0xfc/0x670
? wait_for_completion+0x3b0/0x3b0
? ucma_query_route+0x818/0xc60
ucma_query_route+0x818/0xc60
? ucma_listen+0x1b0/0x1b0
? sched_clock_cpu+0x18/0x1d0
? sched_clock_cpu+0x18/0x1d0
? ucma_listen+0x1b0/0x1b0
? ucma_write+0x292/0x460
ucma_write+0x292/0x460
? ucma_close_id+0x60/0x60
? sched_clock_cpu+0x18/0x1d0
? sched_clock_cpu+0x18/0x1d0
__vfs_write+0xf7/0x620
? ucma_close_id+0x60/0x60
? kernel_read+0x110/0x110
? time_hardirqs_on+0x19/0x580
? lock_acquire+0x18b/0x3a0
? finish_task_switch+0xf3/0x5d0
? _raw_spin_unlock_irq+0x29/0x40
? _raw_spin_unlock_irq+0x29/0x40
? finish_task_switch+0x1be/0x5d0
? __switch_to_asm+0x34/0x70
? __switch_to_asm+0x40/0x70
? security_file_permission+0x172/0x1e0
vfs_write+0x192/0x460
ksys_write+0xc6/0x1a0
? __ia32_sys_read+0xb0/0xb0
? entry_SYSCALL_64_after_hwframe+0x3e/0xbe
? do_syscall_64+0x1d/0x470
do_syscall_64+0x9e/0x470
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x410899
Code: 00 00 48 81 c4 80 00 00 00 e9 f1 fe ff ff 0f 1f 00 48 89 f8 48 89
f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01
f0 ff ff 0f 83 6b 23 00 00 c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffc8d2d4498 EFLAGS: 00000286 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 006d635f616d6472 RCX: 0000000000410899
RDX: 0000000000000018 RSI: 0000000020000080 RDI: 0000000000000039
RBP: 2f646e6162696e69 R08: 00000000004002e0 R09: 00000000004002e0
R10: 00000000004002e0 R11: 0000000000000286 R12: 666e692f7665642f
R13: 0000000000401b80 R14: 0000000000401c10 R15: 0000000000000006
Modules linked in:
Dumping ftrace buffer:
(ftrace buffer empty)
---[ end trace b0e1982aeff8bfd1 ]---
RIP: 0010:ib_copy_path_rec_to_user+0x94/0x3e0
Code: f1 f1 f1 f1 c7 40 0c 00 00 f4 f4 65 48 8b 04 25 28 00 00 00 48 89
45 c8 31 c0 e8 d7 60 24 ff 48 8d 7b 4c 48 89 f8 48 c1 e8 03 <42> 0f b6
14 30 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85
RSP: 0018:ffff88006586f980 EFLAGS: 00010207
RAX: 0000000000000009 RBX: 0000000000000000 RCX: 1ffff1000d5fe475
RDX: ffff8800621e17c0 RSI: ffffffff820d45f9 RDI: 000000000000004c
RBP: ffff88006586fa50 R08: ffffed000cb0df73 R09: ffffed000cb0df72
R10: ffff88006586fa70 R11: ffffed000cb0df73 R12: 1ffff1000cb0df30
R13: ffff88006586fae8 R14: dffffc0000000000 R15: ffff88006aff2200
FS: 00000000016fc880(0000) GS:ffff88006d000000(0000)
knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000040 CR3: 0000000063fec000 CR4: 00000000000006b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled

Fixes: 3c86aa70bf67 ("RDMA/cm: Add RDMA CM support for IBoE devices")
Signed-off-by: Avihai Horon <avihaih@mellanox.com>
Reviewed-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
---
I'm sending it to -next, because this flow existed many years and
doesn't worth to have a merge conflict between -rc and -next.

Thanks
---
 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 8924b2f8e299..8f73a7e87359 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -3007,6 +3007,7 @@ static int cma_resolve_iboe_route(struct rdma_id_private *id_priv)
 err2:
 	kfree(route->path_rec);
 	route->path_rec = NULL;
+	route->num_paths = 0;
 err1:
 	kfree(work);
 	return ret;
--
2.24.1