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Yifei Liu 1cffdf91ca jffs2: correct logic when creating a hole in jffs2_write_begin 
[ Upstream commit 23892d383b ]

Bug description and fix:

1. Write data to a file, say all 1s from offset 0 to 16.

2. Truncate the file to a smaller size, say 8 bytes.

3. Write new bytes (say 2s) from an offset past the original size of the
file, say at offset 20, for 4 bytes.  This is supposed to create a "hole"
in the file, meaning that the bytes from offset 8 (where it was truncated
above) up to the new write at offset 20, should all be 0s (zeros).

4. Flush all caches using "echo 3 > /proc/sys/vm/drop_caches" (or unmount
and remount) the f/s.

5. Check the content of the file.  It is wrong.  The 1s that used to be
between bytes 9 and 16, before the truncation, have REAPPEARED (they should
be 0s).

We wrote a script and helper C program to reproduce the bug
(reproduce_jffs2_write_begin_issue.sh, write_file.c, and Makefile).  We can
make them available to anyone.

The above example is shown when writing a small file within the same first
page.  But the bug happens for larger files, as long as steps 1, 2, and 3
above all happen within the same page.

The problem was traced to the jffs2_write_begin code, where it goes into an
'if' statement intended to handle writes past the current EOF (i.e., writes
that may create a hole).  The code computes a 'pageofs' that is the floor
of the write position (pos), aligned to the page size boundary.  In other
words, 'pageofs' will never be larger than 'pos'.  The code then sets the
internal jffs2_raw_inode->isize to the size of max(current inode size,
pageofs) but that is wrong: the new file size should be the 'pos', which is
larger than both the current inode size and pageofs.

Similarly, the code incorrectly sets the internal jffs2_raw_inode->dsize to
the difference between the pageofs minus current inode size; instead it
should be the current pos minus the current inode size.  Finally,
inode->i_size was also set incorrectly.

The patch below fixes this bug.  The bug was discovered using a new tool
for finding f/s bugs using model checking, called MCFS (Model Checking File
Systems).

Signed-off-by: Yifei Liu <yifeliu@cs.stonybrook.edu>
Signed-off-by: Erez Zadok <ezk@cs.stonybrook.edu>
Signed-off-by: Manish Adkar <madkar@cs.stonybrook.edu>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2023-03-22 13:33:53 +01:00
arch powerpc/mm: Fix false detection of read faults 2023-03-22 13:33:47 +01:00
block block: do not reverse request order when flushing plug list 2023-03-22 13:33:46 +01:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-02-09 11:28:11 +01:00
crypto crypto: rsa-pkcs1pad - Use akcipher_request_complete 2023-03-10 09:33:03 +01:00
Documentation docs: Correct missing "d_" prefix for dentry_operations member d_weak_revalidate 2023-03-22 13:33:40 +01:00
drivers soc: mediatek: mtk-svs: keep svs alive if CONFIG_DEBUG_FS not supported 2023-03-22 13:33:53 +01:00
fs jffs2: correct logic when creating a hole in jffs2_write_begin 2023-03-22 13:33:53 +01:00
include drm/bridge: Fix returned array size name for atomic_get_input_bus_fmts kdoc 2023-03-22 13:33:47 +01:00
init gcc: disable -Warray-bounds for gcc-11 too 2023-01-14 10:33:43 +01:00
io_uring io_uring/uring_cmd: ensure that device supports IOPOLL 2023-03-17 08:50:14 +01:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel watch_queue: fix IOC_WATCH_QUEUE_SET_SIZE alloc error paths 2023-03-17 08:50:30 +01:00
lib sbitmap: Try each queue to wake up at least one waiter 2023-03-10 09:34:34 +01:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm memory tier: release the new_memtier in find_create_memory_tier() 2023-03-10 09:34:27 +01:00
net net/iucv: Fix size of interrupt data 2023-03-22 13:33:50 +01:00
rust rust: print: avoid evaluating arguments in pr_* macros in unsafe blocks 2023-02-06 08:06:34 +01:00
samples ftrace: Export ftrace_free_filter() to modules 2023-02-01 08:34:37 +01:00
scripts kconfig: Update config changed flag before calling callback 2023-03-22 13:33:52 +01:00
security ima: Align ima_file_mmap() parameters with mmap_file LSM hook 2023-03-10 09:34:15 +01:00
sound ALSA: hda: Match only Intel devices with CONTROLLER_IN_GPU() 2023-03-22 13:33:42 +01:00
tools selftests: net: devlink_port_split.py: skip test if no suitable device available 2023-03-22 13:33:50 +01:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt KVM: Register /dev/kvm as the _very_ last thing during initialization 2023-03-10 09:34:11 +01:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS audit: update the mailing list in MAINTAINERS 2023-02-25 11:25:42 +01:00
Makefile Linux 6.1.20 2023-03-17 08:50:33 +01:00
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.