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Linux mainline fork with MSM8998 patches | https://mainline.space | Currently supported devices: OnePlus 5/5T, Xiaomi Mi 6, F(x)tec Pro¹ (2019 QX1000 model) & Sony Xperia XZ Premium (UNTESTED!)
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Jacob Keller 59e1f857e3 ice: remove checks in ice_vc_send_msg_to_vf 
The ice_vc_send_msg_to_vf function is used by the PF to send a response
to a VF. This function has overzealous checks to ensure its not passed a
NULL VF pointer and to ensure that the passed in struct ice_vf has a
valid vf_id sub-member.

These checks have existed since commit 1071a8358a ("ice: Implement
virtchnl commands for AVF support") and function as simple sanity
checks.

We are planning to refactor the ice driver to use a hash table along
with appropriate locks in a future refactor. This change will modify how
the ice_validate_vf_id function works. Instead of a simple >= check to
ensure the VF ID is between some range, it will check the hash table to
see if the specified VF ID is actually in the table. This requires that
the function properly lock the table to prevent race conditions.

The checks may seem ok at first glance, but they don't really provide
much benefit.

In order for ice_vc_send_msg_to_vf to have these checks fail, the
callers must either (1) pass NULL as the VF, (2) construct an invalid VF
pointer manually, or (3) be using a VF pointer which becomes invalid
after they obtain it properly using ice_get_vf_by_id.

For (1), a cursory glance over callers of ice_vc_send_msg_to_vf can show
that in most cases the functions already operate assuming their VF
pointer is valid, such as by derferencing vf->pf or other members.

They obtain the VF pointer by accessing the VF array using the VF ID,
which can never produce a NULL value (since its a simple address
operation on the array it will not be NULL.

The sole exception for (1) is that ice_vc_process_vf_msg will forward a
NULL VF pointer to this function as part of its goto error handler
logic. This requires some minor cleanup to simply exit immediately when
an invalid VF ID is detected (Rather than use the same error flow as
the rest of the function).

For (2), it is unexpected for a flow to construct a VF pointer manually
instead of accessing the VF array. Defending against this is likely to
just hide bad programming.

For (3), it is definitely true that VF pointers could become invalid,
for example if a thread is processing a VF message while the VF gets
removed. However, the correct solution is not to add additional checks
like this which do not guarantee to prevent the race. Instead we plan to
solve the root of the problem by preventing the possibility entirely.

This solution will require the change to a hash table with proper
locking and reference counts of the VF structures. When this is done,
ice_validate_vf_id will require locking of the hash table. This will be
problematic because all of the callers of ice_vc_send_msg_to_vf will
already have to take the lock to obtain the VF pointer anyways. With a
mutex, this leads to a double lock that could hang the kernel thread.

Avoid this by removing the checks which don't provide much value, so
that we can safely add the necessary protections properly.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Konrad Jankowski <konrad0.jankowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
2022-03-03 08:46:48 -08:00
arch Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-02-24 17:54:25 -08:00
block block: clear iocb->private in blkdev_bio_end_io_async() 2022-02-22 06:59:49 -07:00
certs certs: Fix build error when CONFIG_MODULE_SIG_KEY is empty 2022-01-23 00:08:44 +09:00
crypto crypto: af_alg - get rid of alg_memory_allocated 2022-02-15 14:29:04 +00:00
Documentation docs: ABI: Document new timecard sysfs nodes. 2022-03-03 14:42:46 +00:00
drivers ice: remove checks in ice_vc_send_msg_to_vf 2022-03-03 08:46:48 -08:00
fs io_uring-5.17-2022-02-23 2022-02-24 11:08:15 -08:00
include bpf: Add __sk_buff->delivery_time_type and bpf_skb_set_skb_delivery_time() 2022-03-03 14:38:49 +00:00
init Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2022-02-09 18:40:56 -08:00
ipc ipc/sem: do not sleep with a spin lock held 2022-02-04 09:25:05 -08:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-02-24 17:54:25 -08:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-02-24 17:54:25 -08:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm mm: don't try to NUMA-migrate COW pages that have other uses 2022-02-17 08:57:47 -08:00
net bpf: Add __sk_buff->delivery_time_type and bpf_skb_set_skb_delivery_time() 2022-03-03 14:38:49 +00:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-02-17 11:44:20 -08:00
scripts Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-02-17 11:44:20 -08:00
security net: rtnetlink: Add RTM_SETSTATS 2022-03-03 10:37:23 +00:00
sound spi: Make remove() return void 2022-02-28 10:43:07 -08:00
tools bpf: selftests: test skb->tstamp in redirect_neigh 2022-03-03 14:38:49 +00:00
usr kbuild: remove include/linux/cyclades.h from header file check 2022-01-27 08:51:08 +01:00
virt Two larger x86 series: 2022-01-28 19:00:26 +02:00
.clang-format genirq/msi: Make interrupt allocation less convoluted 2021-12-16 22:22:20 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: update Christian Brauner's email address 2022-02-01 11:21:31 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Removing Ohad from remoteproc/rpmsg maintenance 2021-12-08 10:09:40 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS net/fungible: Kconfig, Makefiles, and MAINTAINERS 2022-02-27 10:51:23 +00:00
Makefile Linux 5.17-rc5 2022-02-20 13:07:20 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.