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Filename Latest commit message Latest commit date
Theodore Ts'o 5a016c053f ext4: don't BUG if someone dirty pages without asking ext4 first
[ Upstream commit cc5095747edfb054ca2068d01af20be3fcc3634f ]

[un]pin_user_pages_remote is dirtying pages without properly warning
the file system in advance.  A related race was noted by Jan Kara in
2018[1]; however, more recently instead of it being a very hard-to-hit
race, it could be reliably triggered by process_vm_writev(2) which was
discovered by Syzbot[2].

This is technically a bug in mm/gup.c, but arguably ext4 is fragile in
that if some other kernel subsystem dirty pages without properly
notifying the file system using page_mkwrite(), ext4 will BUG, while
other file systems will not BUG (although data will still be lost).

So instead of crashing with a BUG, issue a warning (since there may be
potential data loss) and just mark the page as clean to avoid
unprivileged denial of service attacks until the problem can be
properly fixed.  More discussion and background can be found in the
thread starting at [2].

[1] https://lore.kernel.org/linux-mm/20180103100430.GE4911@quack2.suse.cz
[2] https://lore.kernel.org/r/Yg0m6IjcNmfaSokM@google.com

Reported-by: syzbot+d59332e2db681cf18f0318a06e994ebbb529a8db@syzkaller.appspotmail.com
Reported-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/YiDS9wVfq4mM2jGK@mit.edu
Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-04-15 14:18:23 +02:00
arch xen: fix is_xen_pmu() 2022-04-15 14:18:21 +02:00
block Revert "Revert "block, bfq: honor already-setup queue merges"" 2022-04-15 14:18:23 +02:00
certs
crypto crypto: authenc - Fix sleep in atomic context in decrypt_tail 2022-04-15 14:18:04 +02:00
Documentation Documentation: update stable tree link 2022-04-15 14:17:58 +02:00
drivers spi: tegra20: Use of_device_get_match_data() 2022-04-15 14:18:23 +02:00
fs ext4: don't BUG if someone dirty pages without asking ext4 first 2022-04-15 14:18:23 +02:00
include PCI: Reduce warnings on possible RW1C corruption 2022-04-15 14:18:15 +02:00
init bpf: Add kconfig knob for disabling unpriv bpf by default 2022-02-16 12:52:49 +01:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-12-01 09:23:35 +01:00
kernel dma-debug: fix return value of __setup handlers 2022-04-15 14:18:18 +02:00
lib lib/raid6/test/Makefile: Use $(pound) instead of \# for Make 4.3 2022-04-15 14:18:23 +02:00
LICENSES
mm mm/kmemleak: reset tag when compare object pointer 2022-04-15 14:18:01 +02:00
net net/x25: Fix null-ptr-deref caused by x25_disconnect 2022-04-15 14:18:21 +02:00
samples samples/kretprobes: Fix return value if register_kretprobe() failed 2021-11-17 09:48:39 +01:00
scripts gcc-plugins/stackleak: Exactly match strings instead of prefixes 2022-04-15 14:18:22 +02:00
security Fix incorrect type in assignment of ipv6 port for audit 2022-04-15 14:18:22 +02:00
sound ASoC: msm8916-wcd-analog: Fix error handling in pm8916_wcd_analog_spmi_probe 2022-04-15 14:18:10 +02:00
tools selftests: test_vxlan_under_vrf: Fix broken test case 2022-04-15 14:18:21 +02:00
usr
virt KVM: arm64: Allow SMCCC_ARCH_WORKAROUND_3 to be discovered and migrated 2022-03-19 13:40:15 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
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COPYING
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Kbuild
Kconfig
MAINTAINERS
Makefile Linux 5.4.188 2022-03-28 08:46:49 +02:00
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.