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Baokun Li 3027e200dd quota: fix dqput() to follow the guarantees dquot_srcu should provide [ Upstream commit `dabc8b2075` ] The dquot_mark_dquot_dirty() using dquot references from the inode should be protected by dquot_srcu. quota_off code takes care to call synchronize_srcu(&dquot_srcu) to not drop dquot references while they are used by other users. But dquot_transfer() breaks this assumption. We call dquot_transfer() to drop the last reference of dquot and add it to free_dquots, but there may still be other users using the dquot at this time, as shown in the function graph below: cpu1 cpu2 _________________\|_________________ wb_do_writeback CHOWN(1) ... ext4_da_update_reserve_space dquot_claim_block ... dquot_mark_dquot_dirty // try to dirty old quota test_bit(DQ_ACTIVE_B, &dquot->dq_flags) // still ACTIVE if (test_bit(DQ_MOD_B, &dquot->dq_flags)) // test no dirty, wait dq_list_lock ... dquot_transfer __dquot_transfer dqput_all(transfer_from) // rls old dquot dqput // last dqput dquot_release clear_bit(DQ_ACTIVE_B, &dquot->dq_flags) atomic_dec(&dquot->dq_count) put_dquot_last(dquot) list_add_tail(&dquot->dq_free, &free_dquots) // add the dquot to free_dquots if (!test_and_set_bit(DQ_MOD_B, &dquot->dq_flags)) add dqi_dirty_list // add released dquot to dirty_list This can cause various issues, such as dquot being destroyed by dqcache_shrink_scan() after being added to free_dquots, which can trigger a UAF in dquot_mark_dquot_dirty(); or after dquot is added to free_dquots and then to dirty_list, it is added to free_dquots again after dquot_writeback_dquots() is executed, which causes the free_dquots list to be corrupted and triggers a UAF when dqcache_shrink_scan() is called for freeing dquot twice. As Honza said, we need to fix dquot_transfer() to follow the guarantees dquot_srcu should provide. But calling synchronize_srcu() directly from dquot_transfer() is too expensive (and mostly unnecessary). So we add dquot whose last reference should be dropped to the new global dquot list releasing_dquots, and then queue work item which would call synchronize_srcu() and after that perform the final cleanup of all the dquots on releasing_dquots. Fixes: `4580b30ea8` ("quota: Do not dirty bad dquots") Suggested-by: Jan Kara <jack@suse.cz> Signed-off-by: Baokun Li <libaokun1@huawei.com> Signed-off-by: Jan Kara <jack@suse.cz> Message-Id: <20230630110822.3881712-5-libaokun1@huawei.com> Signed-off-by: Sasha Levin <sashal@kernel.org>		History 2023-09-13 09:42:36 +02:00
arch	arm64: mm: use ptep_clear() instead of pte_clear() in clear_flush()	2023-09-13 09:42:34 +02:00
block	blk-crypto: dynamically allocate fallback profile	2023-08-23 17:52:39 +02:00
certs	certs: Fix build error when PKCS#11 URI contains semicolon	2023-02-09 11:28:11 +01:00
crypto	crypto: api - Use work queue in crypto_destroy_instance	2023-09-13 09:42:32 +02:00
Documentation	media: uapi: HEVC: Add num_delta_pocs_of_ref_rps_idx field	2023-09-13 09:42:20 +02:00
drivers	drm/bridge: tc358764: Fix debug print parameter order	2023-09-13 09:42:35 +02:00
fs	quota: fix dqput() to follow the guarantees dquot_srcu should provide	2023-09-13 09:42:36 +02:00
include	mac80211: make ieee80211_tx_info padding explicit	2023-09-13 09:42:34 +02:00
init	sched/psi: Select KERNFS as needed	2023-09-13 09:42:28 +02:00
io_uring	io_uring/parisc: Adjust pgoff in io_uring mmap() for parisc	2023-09-02 09:16:19 +02:00
ipc	ipc: fix memory leak in init_mqueue_fs()	2022-12-31 13:32:01 +01:00
kernel	bpf: Fix an error in verifying a field in a union	2023-09-13 09:42:30 +02:00
lib	maple_tree: disable mas_wr_append() when other readers are possible	2023-08-30 16:11:13 +02:00
LICENSES	LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers	2021-12-16 14:33:10 +01:00
mm	net-memcg: Fix scope of sockmem pressure indicators	2023-09-13 09:42:33 +02:00
net	netrom: Deny concurrent connect().	2023-09-13 09:42:35 +02:00
rust	rust: allocator: Prevent mis-aligned allocation	2023-08-11 12:08:18 +02:00
samples	samples/bpf: fix broken map lookup probe	2023-09-13 09:42:34 +02:00
scripts	kbuild: rust_is_available: fix confusion when a version appears in the path	2023-09-13 09:42:32 +02:00
security	vfs, security: Fix automount superblock LSM init problem, preventing NFS sb sharing	2023-09-13 09:42:28 +02:00
sound	ASoC: cs43130: Fix numerator/denominator mixup	2023-09-13 09:42:36 +02:00
tools	selftests/bpf: Clean up fmod_ret in bench_rename test script	2023-09-13 09:42:33 +02:00
usr	usr/gen_init_cpio.c: remove unnecessary -1 values from int file	2022-10-03 14:21:44 -07:00
virt	KVM: Grab a reference to KVM for VM and vCPU stats file descriptors	2023-08-03 10:24:08 +02:00
.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	devlink: move code to a dedicated directory	2023-08-30 16:11:00 +02:00
Makefile	kbuild: rust_is_available: remove -v option	2023-09-13 09:42:32 +02:00
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.