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Thu, 26 Mar 2026 20:33:39 -0700 (PDT) From: Pasha Tatashin To: rppt@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, pasha.tatashin@soleen.com, dmatlack@google.com, pratyush@kernel.org, skhawaja@google.com Subject: [PATCH v3 03/10] liveupdate: Protect file handler list with rwsem Date: Fri, 27 Mar 2026 03:33:27 +0000 Message-ID: <20260327033335.696621-4-pasha.tatashin@soleen.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260327033335.696621-1-pasha.tatashin@soleen.com> References: <20260327033335.696621-1-pasha.tatashin@soleen.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 04FE3C0008 X-Stat-Signature: owj8gaac9zqmkfudhugz4kd9cgj9ec4z X-HE-Tag: 1774582420-323459 X-HE-Meta: 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 8GeH6/+S 18dhr1mj2TYw0PUr5SGMIP6dAoiMqHiimtV1ffF89yzNTAZQ2enz8KS4xs3zRX4nRNyyn6pm2C1tPUU0I60tPDdtBbQWqSEsLdffU4iXBbEBaWCmhbwj8dGliQt0bpoXtvEnm2+uJcWWrkYtXqO7JtJUvBnheL9+xyYO5iIvC1sfLq1PThyr/4p7w5LJ/Gmrsd+LGjDeowhvfAUI97NZHo7ySUueW6gRMC3sdvU3wY/RX5w/fsAo+ixS2JIUPLILj4Srdi7V66nV1CAM7VltP8eleSSO1F+urG0k/uM0hlgPU1YHmzHe3WITLzuCUh2JglLPbFp3X8mH1nrQEe+ejfMVpYWcijt/vt3peXA6dAlLaJlc= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Because liveupdate file handlers will no longer hold a module reference when registered, we must ensure that the access to the handler list is protected against concurrent module unloading. Utilize the global luo_register_rwlock to protect the global registry of file handlers. Read locks are taken during list traversals in luo_preserve_file() and luo_file_deserialize(). Write locks are taken during registration and unregistration. Signed-off-by: Pasha Tatashin --- kernel/liveupdate/luo_core.c | 6 ++++++ kernel/liveupdate/luo_file.c | 22 +++++++++++++++++----- kernel/liveupdate/luo_internal.h | 2 ++ 3 files changed, 25 insertions(+), 5 deletions(-) diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c index dda7bb57d421..f9ae9364a962 100644 --- a/kernel/liveupdate/luo_core.c +++ b/kernel/liveupdate/luo_core.c @@ -54,6 +54,7 @@ #include #include #include +#include #include #include #include @@ -68,6 +69,11 @@ static struct { u64 liveupdate_num; } luo_global; +/* + * luo_register_rwlock - Protects registration of file handlers and FLBs. + */ +DECLARE_RWSEM(luo_register_rwlock); + static int __init early_liveupdate_param(char *buf) { return kstrtobool(buf, &luo_global.enabled); diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c index a6d98fc75d25..4aea17a94b4f 100644 --- a/kernel/liveupdate/luo_file.c +++ b/kernel/liveupdate/luo_file.c @@ -277,12 +277,14 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd) goto err_fput; err = -ENOENT; + down_read(&luo_register_rwlock); list_private_for_each_entry(fh, &luo_file_handler_list, list) { if (fh->ops->can_preserve(fh, file)) { err = 0; break; } } + up_read(&luo_register_rwlock); /* err is still -ENOENT if no handler was found */ if (err) @@ -777,12 +779,14 @@ int luo_file_deserialize(struct luo_file_set *file_set, bool handler_found = false; struct luo_file *luo_file; + down_read(&luo_register_rwlock); list_private_for_each_entry(fh, &luo_file_handler_list, list) { if (!strcmp(fh->compatible, file_ser[i].compatible)) { handler_found = true; break; } } + up_read(&luo_register_rwlock); if (!handler_found) { pr_warn("No registered handler for compatible '%.*s'\n", @@ -851,32 +855,36 @@ int liveupdate_register_file_handler(struct liveupdate_file_handler *fh) if (!luo_session_quiesce()) return -EBUSY; + down_write(&luo_register_rwlock); /* Check for duplicate compatible strings */ list_private_for_each_entry(fh_iter, &luo_file_handler_list, list) { if (!strcmp(fh_iter->compatible, fh->compatible)) { pr_err("File handler registration failed: Compatible string '%s' already registered.\n", fh->compatible); err = -EEXIST; - goto err_resume; + goto err_unlock; } } /* Pin the module implementing the handler */ if (!try_module_get(fh->ops->owner)) { err = -EAGAIN; - goto err_resume; + goto err_unlock; } INIT_LIST_HEAD(&ACCESS_PRIVATE(fh, flb_list)); INIT_LIST_HEAD(&ACCESS_PRIVATE(fh, list)); list_add_tail(&ACCESS_PRIVATE(fh, list), &luo_file_handler_list); + up_write(&luo_register_rwlock); + luo_session_resume(); liveupdate_test_register(fh); return 0; -err_resume: +err_unlock: + up_write(&luo_register_rwlock); luo_session_resume(); return err; } @@ -910,16 +918,20 @@ int liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh) if (!luo_session_quiesce()) goto err_register; + down_write(&luo_register_rwlock); if (!list_empty(&ACCESS_PRIVATE(fh, flb_list))) - goto err_resume; + goto err_unlock; list_del(&ACCESS_PRIVATE(fh, list)); + up_write(&luo_register_rwlock); + module_put(fh->ops->owner); luo_session_resume(); return 0; -err_resume: +err_unlock: + up_write(&luo_register_rwlock); luo_session_resume(); err_register: liveupdate_test_register(fh); diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h index 8083d8739b09..4bfe00ac8866 100644 --- a/kernel/liveupdate/luo_internal.h +++ b/kernel/liveupdate/luo_internal.h @@ -77,6 +77,8 @@ struct luo_session { struct mutex mutex; }; +extern struct rw_semaphore luo_register_rwlock; + int luo_session_create(const char *name, struct file **filep); int luo_session_retrieve(const char *name, struct file **filep); int __init luo_session_setup_outgoing(void *fdt); -- 2.43.0