mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
synced 2025-01-16 13:34:30 +00:00
15bc01effe
In commit fda31c50292a ("signal: avoid double atomic counter
increments for user accounting") Linus made a clever optimization to
how rlimits and the struct user_struct. Unfortunately that
optimization does not work in the obvious way when moved to nested
rlimits. The problem is that the last decrement of the per user
namespace per user sigpending counter might also be the last decrement
of the sigpending counter in the parent user namespace as well. Which
means that simply freeing the leaf ucount in __free_sigqueue is not
enough.
Maintain the optimization and handle the tricky cases by introducing
inc_rlimit_get_ucounts and dec_rlimit_put_ucounts.
By moving the entire optimization into functions that perform all of
the work it becomes possible to ensure that every level is handled
properly.
The new function inc_rlimit_get_ucounts returns 0 on failure to
increment the ucount. This is different than inc_rlimit_ucounts which
increments the ucounts and returns LONG_MAX if the ucount counter has
exceeded it's maximum or it wrapped (to indicate the counter needs to
decremented).
I wish we had a single user to account all pending signals to across
all of the threads of a process so this complexity was not necessary
Cc: stable@vger.kernel.org
Fixes: d64696905554 ("Reimplement RLIMIT_SIGPENDING on top of ucounts")
v1: https://lkml.kernel.org/r/87mtnavszx.fsf_-_@disp2133
Link: https://lkml.kernel.org/r/87fssytizw.fsf_-_@disp2133
Reviewed-by: Alexey Gladkov <legion@kernel.org>
Tested-by: Rune Kleveland <rune.kleveland@infomedia.dk>
Tested-by: Yu Zhao <yuzhao@google.com>
Tested-by: Jordan Glover <Golden_Miller83@protonmail.ch>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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.