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Carlo Nonato 4db2f87e15 block, bfq: fix overwrite of bfq_group pointer in bfq_find_set_group()
[ Upstream commit 14afc59361976c0ba39e3a9589c3eaa43ebc7e1d ]

The bfq_find_set_group() function takes as input a blkcg (which represents
a cgroup) and retrieves the corresponding bfq_group, then it updates the
bfq internal group hierarchy (see comments inside the function for why
this is needed) and finally it returns the bfq_group.
In the hierarchy update cycle, the pointer holding the correct bfq_group
that has to be returned is mistakenly used to traverse the hierarchy
bottom to top, meaning that in each iteration it gets overwritten with the
parent of the current group. Since the update cycle stops at root's
children (depth = 2), the overwrite becomes a problem only if the blkcg
describes a cgroup at a hierarchy level deeper than that (depth > 2). In
this case the root's child that happens to be also an ancestor of the
correct bfq_group is returned. The main consequence is that processes
contained in a cgroup at depth greater than 2 are wrongly placed in the
group described above by BFQ.

This commits fixes this problem by using a different bfq_group pointer in
the update cycle in order to avoid the overwrite of the variable holding
the original group reference.

Reported-by: Kwon Je Oh <kwonje.oh2@gmail.com>
Signed-off-by: Carlo Nonato <carlo.nonato95@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-03-25 08:25:49 +01:00
arch riscv: Fix range looking for kernel image memblock 2020-03-25 08:25:48 +01:00
block block, bfq: fix overwrite of bfq_group pointer in bfq_find_set_group() 2020-03-25 08:25:49 +01:00
certs
crypto
Documentation ACPI: watchdog: Allow disabling WDAT at boot 2020-03-21 08:11:47 +01:00
drivers xenbus: req->err should be updated before req->state 2020-03-25 08:25:49 +01:00
fs cifs: add missing mount option to /proc/mounts 2020-03-25 08:25:43 +01:00
include driver code: clarify and fix platform device DMA mask allocation 2020-03-18 07:17:56 +01:00
init
ipc
kernel signal: avoid double atomic counter increments for user accounting 2020-03-21 08:11:53 +01:00
lib
LICENSES
mm mm: slub: add missing TID bump in kmem_cache_alloc_bulk() 2020-03-21 08:11:58 +01:00
net ipv4: ensure rcu_read_lock() in cipso_v4_error() 2020-03-21 08:11:59 +01:00
samples
scripts
security efi: Only print errors about failing to get certs if EFI vars are found 2020-03-12 13:00:14 +01:00
sound ASoC: stm32: sai: manage rebind issue 2020-03-25 08:25:48 +01:00
tools selftests/rseq: Fix out-of-tree compilation 2020-03-21 08:11:49 +01:00
usr kbuild: fix 'No such file or directory' warning when cleaning 2020-03-12 13:00:09 +01:00
virt KVM: Check for a bad hva before dropping into the ghc slow path 2020-03-05 16:43:48 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile Linux 5.4.27 2020-03-21 08:12:00 +01:00
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.