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Brian Foster c85cbb0b21 xfs: hold buffer across unpin and potential shutdown processing commit `84d8949e77` upstream. The special processing used to simulate a buffer I/O failure on fs shutdown has a difficult to reproduce race that can result in a use after free of the associated buffer. Consider a buffer that has been committed to the on-disk log and thus is AIL resident. The buffer lands on the writeback delwri queue, but is subsequently locked, committed and pinned by another transaction before submitted for I/O. At this point, the buffer is stuck on the delwri queue as it cannot be submitted for I/O until it is unpinned. A log checkpoint I/O failure occurs sometime later, which aborts the bli. The unpin handler is called with the aborted log item, drops the bli reference count, the pin count, and falls into the I/O failure simulation path. The potential problem here is that once the pin count falls to zero in ->iop_unpin(), xfsaild is free to retry delwri submission of the buffer at any time, before the unpin handler even completes. If delwri queue submission wins the race to the buffer lock, it observes the shutdown state and simulates the I/O failure itself. This releases both the bli and delwri queue holds and frees the buffer while xfs_buf_item_unpin() sits on xfs_buf_lock() waiting to run through the same failure sequence. This problem is rare and requires many iterations of fstest generic/019 (which simulates disk I/O failures) to reproduce. To avoid this problem, grab a hold on the buffer before the log item is unpinned if the associated item has been aborted and will require a simulated I/O failure. The hold is already required for the simulated I/O failure, so the ordering simply guarantees the unpin handler access to the buffer before it is unpinned and thus processed by the AIL. This particular ordering is required so long as the AIL does not acquire a reference on the bli, which is the long term solution to this problem. Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Acked-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2022-08-03 12:00:51 +02:00
arch	ARM: 9216/1: Fix MAX_DMA_ADDRESS overflow	2022-08-03 12:00:50 +02:00
block	block: Fix handling of offline queues in blk_mq_alloc_request_hctx()	2022-06-22 14:13:17 +02:00
certs	certs/blacklist_hashes.c: fix const confusion in certs blacklist	2022-06-22 14:13:17 +02:00
crypto	crypto: memneq - move into lib/	2022-06-22 14:13:18 +02:00
Documentation	docs/kernel-parameters: Update descriptions for "mitigations=" param with retbleed	2022-08-03 12:00:50 +02:00
drivers	EDAC/ghes: Set the DIMM label unconditionally	2022-08-03 12:00:50 +02:00
fs	xfs: hold buffer across unpin and potential shutdown processing	2022-08-03 12:00:51 +02:00
include	ipv6/addrconf: fix a null-ptr-deref bug for ip6_ptr	2022-08-03 12:00:46 +02:00
init	Kconfig: Add option for asm goto w/ tied outputs to workaround clang-13 bug	2022-06-09 10:21:25 +02:00
ipc	ipc/mqueue: use get_tree_nodev() in mqueue_get_tree()	2022-06-09 10:21:17 +02:00
kernel	watch_queue: Fix missing locking in add_watch_to_object()	2022-08-03 12:00:44 +02:00
lib	ida: don't use BUG_ON() for debugging	2022-07-12 16:32:23 +02:00
LICENSES	LICENSES/deprecated: add Zlib license text	2020-09-16 14:33:49 +02:00
mm	page_alloc: fix invalid watermark check on a negative value	2022-08-03 12:00:50 +02:00
net	sctp: leave the err path free in sctp_stream_init to sctp_stream_free	2022-08-03 12:00:49 +02:00
samples	x86: Prepare inline-asm for straight-line-speculation	2022-07-25 11:26:29 +02:00
scripts	x86/retbleed: Add fine grained Kconfig knobs	2022-07-25 11:26:50 +02:00
security	lockdown: Fix kexec lockdown bypass with ima policy	2022-07-29 17:19:06 +02:00
sound	ALSA: memalloc: Align buffer allocations in page size	2022-07-29 17:19:25 +02:00
tools	perf symbol: Correct address for bss symbols	2022-08-03 12:00:49 +02:00
usr	usr/include/Makefile: add linux/nfc.h to the compile-test coverage	2022-02-01 17:25:48 +01:00
virt	KVM: Don't null dereference ops->destroy	2022-07-29 17:19:23 +02:00
.clang-format	RDMA 5.10 pull request	2020-10-17 11:18:18 -07:00
.cocciconfig
.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	kbuild: generate Module.symvers only when vmlinux exists	2021-05-19 10:12:59 +02:00
.mailmap	mailmap: add two more addresses of Uwe Kleine-König	2020-12-06 10:19:07 -08:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	MAINTAINERS: Move Jason Cooper to CREDITS	2020-11-30 10:20:34 +01:00
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	MAINTAINERS: add Amir as xfs maintainer for 5.10.y	2022-07-02 16:39:22 +02:00
Makefile	Linux 5.10.134	2022-07-29 17:19:29 +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.