Description
In the Linux kernel, the following vulnerability has been resolved: nfs: fix UAF in direct writes In production we have been hitting the following warning consistently ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 17 PID: 1800359 at lib/refcount.c:28 refcount_warn_saturate+0x9c/0xe0 Workqueue: nfsiod nfs_direct_write_schedule_work [nfs] RIP: 0010:refcount_warn_saturate+0x9c/0xe0 PKRU: 55555554 Call Trace: <TASK> ? __warn+0x9f/0x130 ? refcount_warn_saturate+0x9c/0xe0 ? report_bug+0xcc/0x150 ? handle_bug+0x3d/0x70 ? exc_invalid_op+0x16/0x40 ? asm_exc_invalid_op+0x16/0x20 ? refcount_warn_saturate+0x9c/0xe0 nfs_direct_write_schedule_work+0x237/0x250 [nfs] process_one_work+0x12f/0x4a0 worker_thread+0x14e/0x3b0 ? ZSTD_getCParams_internal+0x220/0x220 kthread+0xdc/0x120 ? __btf_name_valid+0xa0/0xa0 ret_from_fork+0x1f/0x30 This is because we're completing the nfs_direct_request twice in a row. The source of this is when we have our commit requests to submit, we process them and send them off, and then in the completion path for the commit requests we have if (nfs_commit_end(cinfo.mds)) nfs_direct_write_complete(dreq); However since we're submitting asynchronous requests we sometimes have one that completes before we submit the next one, so we end up calling complete on the nfs_direct_request twice. The only other place we use nfs_generic_commit_list() is in __nfs_commit_inode, which wraps this call in a nfs_commit_begin(); nfs_commit_end(); Which is a common pattern for this style of completion handling, one that is also repeated in the direct code with get_dreq()/put_dreq() calls around where we process events as well as in the completion paths. Fix this by using the same pattern for the commit requests. Before with my 200 node rocksdb stress running this warning would pop every 10ish minutes. With my patch the stress test has been running for several hours without popping.
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
af7cf057933f01dc7f33ddfb5e436ad598ed17ad to < 6cd3f13aaa62970b5169d990e936b2e96943bc6aaffectedaf7cf057933f01dc7f33ddfb5e436ad598ed17ad to < 4595d90b5d2ea5fa4d318d13f59055aa4bf3e7f5affectedaf7cf057933f01dc7f33ddfb5e436ad598ed17ad to < 80d24b308b7ee7037fc90d8ac99f6f78df0a256faffectedaf7cf057933f01dc7f33ddfb5e436ad598ed17ad to < 3abc2d160ed8213948b147295d77d44a22c88fa3affectedaf7cf057933f01dc7f33ddfb5e436ad598ed17ad to < e25447c35f8745337ea8bc0c9697fcac14df8605affectedaf7cf057933f01dc7f33ddfb5e436ad598ed17ad to < 1daf52b5ffb24870fbeda20b4967526d8f9e12abaffectedaf7cf057933f01dc7f33ddfb5e436ad598ed17ad to < cf54f66e1dd78990ec6b32177bca7e6ea2144a95affectedaf7cf057933f01dc7f33ddfb5e436ad598ed17ad to < 17f46b803d4f23c66cacce81db35fef3adb8f2afaffected
Linux Linux
Default version status: affected
4.5affected0 to < 4.5unaffected5.4.297 to ≤ 5.4.*unaffected5.10.215 to ≤ 5.10.*unaffected5.15.154 to ≤ 5.15.*unaffected6.1.84 to ≤ 6.1.*unaffected6.6.24 to ≤ 6.6.*unaffected6.7.12 to ≤ 6.7.*unaffected6.8.3 to ≤ 6.8.*unaffected6.9 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/6cd3f13aaa62970b5169d990e936b2e96943bc6a ↗
- https://git.kernel.org/stable/c/4595d90b5d2ea5fa4d318d13f59055aa4bf3e7f5 ↗
- https://git.kernel.org/stable/c/80d24b308b7ee7037fc90d8ac99f6f78df0a256f ↗
- https://git.kernel.org/stable/c/3abc2d160ed8213948b147295d77d44a22c88fa3 ↗
- https://git.kernel.org/stable/c/e25447c35f8745337ea8bc0c9697fcac14df8605 ↗
- https://git.kernel.org/stable/c/1daf52b5ffb24870fbeda20b4967526d8f9e12ab ↗
- https://git.kernel.org/stable/c/cf54f66e1dd78990ec6b32177bca7e6ea2144a95 ↗
- https://git.kernel.org/stable/c/17f46b803d4f23c66cacce81db35fef3adb8f2af ↗
- https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html ↗
- https://cert-portal.siemens.com/productcert/html/ssa-265688.html ↗