mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-05-14 01:49:20 -04:00
5bd8de2077
The function gets number of online CPUS, and uses it to search for Nth cpu in cpu_online_mask. If id == num_online_cpus() - 1, and one CPU gets offlined between calling num_online_cpus() -> cpumask_nth(), there's a chance for cpumask_nth() to find nothing and return >= nr_cpu_ids. The caller code in __queue_work() tries to avoid that by checking the returned CPU against WORK_CPU_UNBOUND, which is NR_CPUS. It's not the same as '>= nr_cpu_ids'. On a typical Ubuntu desktop, NR_CPUS is 8192, while nr_cpu_ids is the actual number of possible CPUs, say 8. The non-existing cpu may later be passed to rcu_dereference() and corrupt the logic. Fix it by switching from 'if' to 'while'. Suggested-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Link: https://patch.msgid.link/20250910013644.4153708-3-Jason@zx2c4.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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.