android_kernel_motorola_sm6375

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Filename	Latest commit message	Latest commit date
Paul Gortmaker eef99860c6 cgroup1: fix leaked context root causing sporadic NULL deref in LTP commit 1e7107c5ef44431bc1ebbd4c353f1d7c22e5f2ec upstream. Richard reported sporadic (roughly one in 10 or so) null dereferences and other strange behaviour for a set of automated LTP tests. Things like: BUG: kernel NULL pointer dereference, address: 0000000000000008 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP PTI CPU: 0 PID: 1516 Comm: umount Not tainted 5.10.0-yocto-standard #1 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-48-gd9c812dda519-prebuilt.qemu.org 04/01/2014 RIP: 0010:kernfs_sop_show_path+0x1b/0x60 ...or these others: RIP: 0010:do_mkdirat+0x6a/0xf0 RIP: 0010:d_alloc_parallel+0x98/0x510 RIP: 0010:do_readlinkat+0x86/0x120 There were other less common instances of some kind of a general scribble but the common theme was mount and cgroup and a dubious dentry triggering the NULL dereference. I was only able to reproduce it under qemu by replicating Richard's setup as closely as possible - I never did get it to happen on bare metal, even while keeping everything else the same. In commit `71d883c37e` ("cgroup_do_mount(): massage calling conventions") we see this as a part of the overall change: -------------- struct cgroup_subsys ss; - struct dentry dentry; [...] - dentry = cgroup_do_mount(&cgroup_fs_type, fc->sb_flags, root, - CGROUP_SUPER_MAGIC, ns); [...] - if (percpu_ref_is_dying(&root->cgrp.self.refcnt)) { - struct super_block sb = dentry->d_sb; - dput(dentry); + ret = cgroup_do_mount(fc, CGROUP_SUPER_MAGIC, ns); + if (!ret && percpu_ref_is_dying(&root->cgrp.self.refcnt)) { + struct super_block sb = fc->root->d_sb; + dput(fc->root); deactivate_locked_super(sb); msleep(10); return restart_syscall(); } -------------- In changing from the local "*dentry" variable to using fc->root, we now export/leave that dentry pointer in the file context after doing the dput() in the unlikely "is_dying" case. With LTP doing a crazy amount of back to back mount/unmount [testcases/bin/cgroup_regression_5_1.sh] the unlikely becomes slightly likely and then bad things happen. A fix would be to not leave the stale reference in fc->root as follows: -------------- dput(fc->root); + fc->root = NULL; deactivate_locked_super(sb); -------------- ...but then we are just open-coding a duplicate of fc_drop_locked() so we simply use that instead. Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Tejun Heo <tj@kernel.org> Cc: Zefan Li <lizefan.x@bytedance.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: stable@vger.kernel.org # v5.1+ Reported-by: Richard Purdie <richard.purdie@linuxfoundation.org> Fixes: `71d883c37e` ("cgroup_do_mount(): massage calling conventions") Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2021-07-31 08:19:37 +02:00
arch	KVM: x86: determine if an exception has an error code only when injecting it.	2021-07-31 08:19:37 +02:00
block	rq-qos: fix missed wake-ups in rq_qos_throttle try two	2021-07-19 08:53:16 +02:00
certs	certs: Move load_system_certificate_list to a common function	2021-06-30 08:47:55 -04:00
crypto	crypto: shash - avoid comparing pointers to exported functions under CFI	2021-07-14 16:53:13 +02:00
Documentation	userfaultfd: do not untag user pointers	2021-07-28 13:31:01 +02:00
drivers	xhci: add xhci_get_virt_ep() helper	2021-07-28 13:31:02 +02:00
fs	cgroup1: fix leaked context root causing sporadic NULL deref in LTP	2021-07-31 08:19:37 +02:00
include	cgroup1: fix leaked context root causing sporadic NULL deref in LTP	2021-07-31 08:19:37 +02:00
init
ipc
kernel	cgroup1: fix leaked context root causing sporadic NULL deref in LTP	2021-07-31 08:19:37 +02:00
lib	lib/decompress_unlz4.c: correctly handle zero-padding around initrds.	2021-07-20 16:10:46 +02:00
LICENSES
mm	mm: slab: fix kmem_cache_create failed when sysfs node not destroyed	2021-07-25 14:35:14 +02:00
net	af_unix: fix garbage collect vs MSG_PEEK	2021-07-31 08:19:37 +02:00
samples	samples/bpf: Fix the error return code of xdp_redirect's main()	2021-07-14 16:53:30 +02:00
scripts	kbuild: mkcompile_h: consider timestamp if KBUILD_BUILD_TIMESTAMP is set	2021-07-25 14:35:12 +02:00
security	smackfs: restrict bytes count in smk_set_cipso()	2021-07-19 08:53:18 +02:00
sound	ALSA: hdmi: Expose all pins on MSI MS-7C94 board	2021-07-28 13:30:59 +02:00
tools	tools: Allow proper CC/CXX/... override with LLVM=1 in Makefile.include	2021-07-31 08:19:37 +02:00
usr
virt	KVM: mmio: Fix use-after-free Read in kvm_vm_ioctl_unregister_coalesced_mmio	2021-07-20 16:10:40 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile	Linux 5.4.136	2021-07-28 13:31:02 +02:00
README

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.