Description
In the Linux kernel, the following vulnerability has been resolved: nfsd: provide locking for v4_end_grace Writing to v4_end_grace can race with server shutdown and result in memory being accessed after it was freed - reclaim_str_hashtbl in particularly. We cannot hold nfsd_mutex across the nfsd4_end_grace() call as that is held while client_tracking_op->init() is called and that can wait for an upcall to nfsdcltrack which can write to v4_end_grace, resulting in a deadlock. nfsd4_end_grace() is also called by the landromat work queue and this doesn't require locking as server shutdown will stop the work and wait for it before freeing anything that nfsd4_end_grace() might access. However, we must be sure that writing to v4_end_grace doesn't restart the work item after shutdown has already waited for it. For this we add a new flag protected with nn->client_lock. It is set only while it is safe to make client tracking calls, and v4_end_grace only schedules work while the flag is set with the spinlock held. So this patch adds a nfsd_net field "client_tracking_active" which is set as described. Another field "grace_end_forced", is set when v4_end_grace is written. After this is set, and providing client_tracking_active is set, the laundromat is scheduled. This "grace_end_forced" field bypasses other checks for whether the grace period has finished. This resolves a race which can result in use-after-free.
Product status
7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 (git) before ca97360860eb02e3ae4ba42c19b439a0fcecbf06
7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 (git) before e8bfa2401d4c51eca6e48e9b33c798828ca9df61
7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 (git) before 34eb22836e0cdba093baac66599d68c4cd245a9d
7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 (git) before 06600719d0f7a723811c45e4d51f5b742f345309
7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 (git) before ba4811c8b433bfa681729ca42cc62b6034f223b0
7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 (git) before 53f07d095e7e680c5e4569a55a019f2c0348cdc6
7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 (git) before 2857bd59feb63fcf40fe4baf55401baea6b4feb4
3.18
Any version before 3.18
5.10.248 (semver)
5.15.198 (semver)
6.1.161 (semver)
6.6.121 (semver)
6.12.66 (semver)
6.18.6 (semver)
6.19 (original_commit_for_fix)
References
git.kernel.org/...c/ca97360860eb02e3ae4ba42c19b439a0fcecbf06
git.kernel.org/...c/e8bfa2401d4c51eca6e48e9b33c798828ca9df61
git.kernel.org/...c/34eb22836e0cdba093baac66599d68c4cd245a9d
git.kernel.org/...c/06600719d0f7a723811c45e4d51f5b742f345309
git.kernel.org/...c/ba4811c8b433bfa681729ca42cc62b6034f223b0
git.kernel.org/...c/53f07d095e7e680c5e4569a55a019f2c0348cdc6
git.kernel.org/...c/2857bd59feb63fcf40fe4baf55401baea6b4feb4