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Marco Elver 8dbd7603e4 kcsan, seqlock: Fix incorrect assumption in read_seqbegin() 
[ Upstream commit 183ec5f26b ]

During testing of the preceding changes, I noticed that in some cases,
current->kcsan_ctx.in_flat_atomic remained true until task exit. This is
obviously wrong, because _all_ accesses for the given task will be
treated as atomic, resulting in false negatives i.e. missed data races.

Debugging led to fs/dcache.c, where we can see this usage of seqlock:

	struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
	{
		struct dentry *dentry;
		unsigned seq;

		do {
			seq = read_seqbegin(&rename_lock);
			dentry = __d_lookup(parent, name);
			if (dentry)
				break;
		} while (read_seqretry(&rename_lock, seq));
	[...]

As can be seen, read_seqretry() is never called if dentry != NULL;
consequently, current->kcsan_ctx.in_flat_atomic will never be reset to
false by read_seqretry().

Give up on the wrong assumption of "assume closing read_seqretry()", and
rely on the already-present annotations in read_seqcount_begin/retry().

Fixes: 88ecd153be ("seqlock, kcsan: Add annotations for KCSAN")
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241104161910.780003-6-elver@google.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2024-12-05 14:01:23 +01:00
arch locking/atomic/x86: Use ALT_OUTPUT_SP() for __arch_{,try_}cmpxchg64_emu() 2024-12-05 14:01:22 +01:00
block block: fix bio_split_rw_at to take zone_write_granularity into account 2024-12-05 14:01:14 +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 kcsan, seqlock: Support seqcount_latch_t 2024-12-05 14:01:22 +01:00
drivers crypto: cavium - Fix an error handling path in cpt_ucode_load_fw() 2024-12-05 14:01:21 +01:00
fs ext4: fix race in buffer_head read fault injection 2024-12-05 14:01:15 +01:00
include
init initramfs: avoid filename buffer overrun 2024-12-05 14:01:12 +01:00
io_uring io_uring/rw: fix missing NOWAIT check for O_DIRECT start write 2024-10-31 08:21:02 -06:00
ipc struct fd layout change (and conversion to accessor helpers) 2024-09-23 09:35:36 -07:00
kernel timers: Add missing READ_ONCE() in __run_timer_base() 2024-12-05 14:01:22 +01:00
lib objpool: fix to make percpu slot allocation more robust 2024-11-07 14:14:58 -08:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm/mmap: fix __mmap_region() error handling in rare merge failure case 2024-11-22 15:30:26 +01:00
net hv_sock: Initializing vsk->trans to NULL to prevent a dangling pointer 2024-11-22 15:30:25 +01:00
rust Driver core fix for 6.12-rc3 2024-10-13 09:10:52 -07:00
samples Including fixes from bluetooth. 2024-11-14 10:05:33 -08:00
scripts Revert "scripts/faddr2line: Check only two symbols when calculating symbol size" 2024-12-05 14:01:21 +01:00
security integrity-v6.12 2024-11-12 13:06:31 -08:00
sound ASoC: Fixes for v6.12 2024-11-14 16:40:15 +01:00
tools thermal/lib: Fix memory leak on error in thermal_genl_auto() 2024-12-05 14:01:21 +01:00
usr initramfs: shorten cmd_initfs in usr/Makefile 2024-07-16 01:07:52 +09:00
virt ARM64: 2024-10-21 11:22:04 -07:00
.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: appoint myself the XFS maintainer for 6.12 LTS 2024-12-05 14:01:10 +01:00
Makefile Linux 6.12.1 2024-11-22 15:30:26 +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.