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Brian Foster b6ce2dbe98 ext4: partial zero eof block on unaligned inode size extension 
[ Upstream commit c7fc0366c6 ]

Using mapped writes, it's technically possible to expose stale
post-eof data on a truncate up operation. Consider the following
example:

$ xfs_io -fc "pwrite 0 2k" -c "mmap 0 4k" -c "mwrite 2k 2k" \
	-c "truncate 8k" -c "pread -v 2k 16" <file>
...
00000800:  58 58 58 58 58 58 58 58 58 58 58 58 58 58 58 58  XXXXXXXXXXXXXXXX
...

This shows that the post-eof data written via mwrite lands within
EOF after a truncate up. While this is deliberate of the test case,
behavior is somewhat unpredictable because writeback does post-eof
zeroing, and writeback can occur at any time in the background. For
example, an fsync inserted between the mwrite and truncate causes
the subsequent read to instead return zeroes. This basically means
that there is a race window in this situation between any subsequent
extending operation and writeback that dictates whether post-eof
data is exposed to the file or zeroed.

To prevent this problem, perform partial block zeroing as part of
the various inode size extending operations that are susceptible to
it. For truncate extension, zero around the original eof similar to
how truncate down does partial zeroing of the new eof. For extension
via writes and fallocate related operations, zero the newly exposed
range of the file to cover any partial zeroing that must occur at
the original and new eof blocks.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Link: https://patch.msgid.link/20240919160741.208162-2-bfoster@redhat.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2024-12-14 20:03:36 +01:00
arch s390/cpum_sf: Handle CPU hotplug remove during sampling 2024-12-14 20:03:35 +01:00
block block: RCU protect disk->conv_zones_bitmap 2024-12-14 20:03:35 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: pcrypt - Call crypto layer directly when padata_do_parallel() return -EBUSY 2024-12-05 14:01:18 +01:00
Documentation dt-bindings: net: fec: add pps channel property 2024-12-09 10:41:11 +01:00
drivers scsi: ufs: pltfrm: Drop PM runtime reference count after ufshcd_remove() 2024-12-14 20:03:34 +01:00
fs
include block: RCU protect disk->conv_zones_bitmap 2024-12-14 20:03:35 +01:00
init Compiler Attributes: disable __counted_by for clang < 19.1.3 2024-12-05 14:02:45 +01:00
io_uring io_uring: Change res2 parameter type in io_uring_cmd_done 2024-12-14 20:03:26 +01:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-05 14:03:02 +01:00
kernel sched/numa: fix memory leak due to the overwritten vma->numab_state 2024-12-14 20:03:32 +01:00
lib lib: stackinit: hide never-taken branch from compiler 2024-12-14 20:03:32 +01:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm memblock: allow zero threshold in validate_numa_converage() 2024-12-14 20:03:34 +01:00
net xsk: fix OOB map writes when deleting elements 2024-12-14 20:03:31 +01:00
rust rust: enable arbitrary_self_types and remove Receiver 2024-12-14 20:03:34 +01:00
samples kfifo: don't include dma-mapping.h in kfifo.h 2024-12-05 14:03:03 +01:00
scripts rust: enable arbitrary_self_types and remove Receiver 2024-12-14 20:03:34 +01:00
security apparmor: test: Fix memory leak for aa_unpack_strdup() 2024-12-05 14:02:46 +01:00
sound ALSA: hda/realtek: Add support for Samsung Galaxy Book3 360 (NP730QFG) 2024-12-14 20:03:23 +01:00
tools kselftest/arm64: Don't leak pipe fds in pac.exec_sign_all() 2024-12-14 20:03:36 +01:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt KVM: x86: switch hugepage recovery thread to vhost_task 2024-12-05 14:02:43 +01:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Kbuild updates for v6.12 2024-09-24 13:02:06 -07:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -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 self from DSA entry 2024-11-03 12:52:38 -08:00
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 MAINTAINERS: update location of media main tree 2024-12-05 14:02:42 +01:00
Makefile rust: allow clippy::needless_lifetimes 2024-12-14 20:03:20 +01:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.