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.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 to < ca97360860eb02e3ae4ba42c19b439a0fcecbf06affected7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 to < e8bfa2401d4c51eca6e48e9b33c798828ca9df61affected7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 to < 34eb22836e0cdba093baac66599d68c4cd245a9daffected7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 to < 06600719d0f7a723811c45e4d51f5b742f345309affected7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 to < ba4811c8b433bfa681729ca42cc62b6034f223b0affected7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 to < 53f07d095e7e680c5e4569a55a019f2c0348cdc6affected7f5ef2e900d9462bf9cffaf6bb246ed87a20a6d6 to < 2857bd59feb63fcf40fe4baf55401baea6b4feb4affected
Linux Linux
Default version status: affected
3.18affected0 to < 3.18unaffected5.10.248 to ≤ 5.10.*unaffected5.15.198 to ≤ 5.15.*unaffected6.1.161 to ≤ 6.1.*unaffected6.6.121 to ≤ 6.6.*unaffected6.12.66 to ≤ 6.12.*unaffected6.18.6 to ≤ 6.18.*unaffected6.19 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/ca97360860eb02e3ae4ba42c19b439a0fcecbf06 ↗
- https://git.kernel.org/stable/c/e8bfa2401d4c51eca6e48e9b33c798828ca9df61 ↗
- https://git.kernel.org/stable/c/34eb22836e0cdba093baac66599d68c4cd245a9d ↗
- https://git.kernel.org/stable/c/06600719d0f7a723811c45e4d51f5b742f345309 ↗
- https://git.kernel.org/stable/c/ba4811c8b433bfa681729ca42cc62b6034f223b0 ↗
- https://git.kernel.org/stable/c/53f07d095e7e680c5e4569a55a019f2c0348cdc6 ↗
- https://git.kernel.org/stable/c/2857bd59feb63fcf40fe4baf55401baea6b4feb4 ↗
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html ↗
- https://cert-portal.siemens.com/productcert/html/ssa-457936.html ↗