Subject: CVE-2021-47197: net/mlx5e: nullify cq->dbg pointer in mlx5_debug_cq_remove()

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

net/mlx5e: nullify cq->dbg pointer in mlx5_debug_cq_remove()

Prior to this patch in case mlx5_core_destroy_cq() failed it proceeds
to rest of destroy operations. mlx5_core_destroy_cq() could be called again
by user and cause additional call of mlx5_debug_cq_remove().
cq->dbg was not nullify in previous call and cause the crash.

Fix it by nullify cq->dbg pointer after removal.

Also proceed to destroy operations only if FW return 0
for MLX5_CMD_OP_DESTROY_CQ command.

general protection fault, probably for non-canonical address 0x2000300004058: 0000 [#1] SMP PTI
CPU: 5 PID: 1228 Comm: python Not tainted 5.15.0-rc5_for_upstream_min_debug_2021_10_14_11_06 #1
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
RIP: 0010:lockref_get+0x1/0x60
Code: 5d e9 53 ff ff ff 48 8d 7f 70 e8 0a 2e 48 00 c7 85 d0 00 00 00 02
00 00 00 c6 45 70 00 fb 5d c3 c3 cc cc cc cc cc cc cc cc 53 <48> 8b 17
48 89 fb 85 d2 75 3d 48 89 d0 bf 64 00 00 00 48 89 c1 48
RSP: 0018:ffff888137dd7a38 EFLAGS: 00010206
RAX: 0000000000000000 RBX: ffff888107d5f458 RCX: 00000000fffffffe
RDX: 000000000002c2b0 RSI: ffffffff8155e2e0 RDI: 0002000300004058
RBP: ffff888137dd7a88 R08: 0002000300004058 R09: ffff8881144a9f88
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881141d4000
R13: ffff888137dd7c68 R14: ffff888137dd7d58 R15: ffff888137dd7cc0
FS:  00007f4644f2a4c0(0000) GS:ffff8887a2d40000(0000)
knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055b4500f4380 CR3: 0000000114f7a003 CR4: 0000000000170ea0
Call Trace:
  simple_recursive_removal+0x33/0x2e0
  ? debugfs_remove+0x60/0x60
  debugfs_remove+0x40/0x60
  mlx5_debug_cq_remove+0x32/0x70 [mlx5_core]
  mlx5_core_destroy_cq+0x41/0x1d0 [mlx5_core]
  devx_obj_cleanup+0x151/0x330 [mlx5_ib]
  ? __pollwait+0xd0/0xd0
  ? xas_load+0x5/0x70
  ? xa_load+0x62/0xa0
  destroy_hw_idr_uobject+0x20/0x80 [ib_uverbs]
  uverbs_destroy_uobject+0x3b/0x360 [ib_uverbs]
  uobj_destroy+0x54/0xa0 [ib_uverbs]
  ib_uverbs_cmd_verbs+0xaf2/0x1160 [ib_uverbs]
  ? uverbs_finalize_object+0xd0/0xd0 [ib_uverbs]
  ib_uverbs_ioctl+0xc4/0x1b0 [ib_uverbs]
  __x64_sys_ioctl+0x3e4/0x8e0

The Linux kernel CVE team has assigned CVE-2021-47197 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.10.75 with commit 4f7bddf8c5c0 and fixed in 5.10.82 with commit 471c49289055
	Issue introduced in 5.15 with commit 94b960b9deff and fixed in 5.15.5 with commit 2ae381570806
	Issue introduced in 5.15 with commit 94b960b9deff and fixed in 5.16 with commit 76ded29d3fcd
	Issue introduced in 5.14.14 with commit ed8aafea4fec

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2021-47197
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/net/ethernet/mellanox/mlx5/core/cq.c
	drivers/net/ethernet/mellanox/mlx5/core/debugfs.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/471c492890557bd58f73314bb4ad85d5a8fd5026
	https://git.kernel.org/stable/c/2ae38157080616a13a9fe3f0b4b6ec0070aa408a
	https://git.kernel.org/stable/c/76ded29d3fcda4928da8849ffc446ea46871c1c2