Messages in this thread | | | From | (Eric W. Biederman) | Date | Thu, 21 Oct 2021 11:02:14 -0500 | Subject | [GIT PULL] ucount fixes for v5.15 |
| |
Linus,
Please pull the ucount-fixes-for-v5.15 branch from the git tree:
git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git ucount-fixes-for-v5.15
HEAD: 5ebcbe342b1c12fae44b4f83cbeae1520e09857e ucounts: Move get_ucounts from cred_alloc_blank to key_change_session_keyring
There has been one very hard to track down bug in the ucount code that we have been tracking since roughly v5.14 was released. Alex managed to find a reliable reproducer a few days ago and then I was able to instrument the code and figure out what the issue was.
It turns out the sigqueue_alloc single atomic operation optimization did not play nicely with ucounts multiple level rlimits. It turned out that either sigqueue_alloc or sigqueue_free could be operating on multiple levels and trigger the conditions for the optimization on more than one level at the same time.
To deal with that situation I have introduced inc_rlimit_get_ucounts and dec_rlimit_put_ucounts that just focuses on the optimization and the rlimit and ucount changes.
While looking into the big bug I found I couple of other little issues so I am including those fixes here as well.
When I have time I would very much like to dig into process ownership of the shared signal queue and see if we could pick a single owner for the entire queue so that all of the rlimits can count to that owner. Which should entirely remove the need to call get_ucounts and put_ucounts in sigqueue_alloc and sigqueue_free. It is difficult because Linux unlike POSIX supports setuid that works on a single thread.
Eric W. Biederman (4): ucounts: Fix signal ucount refcounting ucounts: Pair inc_rlimit_ucounts with dec_rlimit_ucoutns in commit_creds ucounts: Proper error handling in set_cred_ucounts ucounts: Move get_ucounts from cred_alloc_blank to key_change_session_keyring
kernel/cred.c | 9 ++++----- security/keys/process_keys.c | 8 ++++++++ 2 files changed, 12 insertions(+), 5 deletions(-)
Eric
| |