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[34.150.233.57]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-64e91be0e91sm1672028d50.15.2026.03.18.07.16.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Mar 2026 07:16:56 -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 Subject: [PATCH v2 1/8] liveupdate: Protect file handler list with rwsem Date: Wed, 18 Mar 2026 10:16:39 -0400 Message-ID: <20260318141637.1870220-11-pasha.tatashin@soleen.com> X-Mailer: git-send-email 2.53.0.851.ga537e3e6e9-goog In-Reply-To: <20260318141637.1870220-10-pasha.tatashin@soleen.com> References: <20260318141637.1870220-10-pasha.tatashin@soleen.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3964; i=pasha.tatashin@soleen.com; h=from:subject; bh=y4zQEtLWwPUjJBuJnMG9ipPgnd1TGVtuadyV/PXw3kM=; b=owEBbQKS/ZANAwAKAbt3KEzbc3reAcsmYgBpurPHexu5NubYp4ky/9rJqctDslv7e0bZpiVBP geJyNZcDy+JAjMEAAEKAB0WIQRBMaqT7LRvGvB/NmK7dyhM23N63gUCabqzxwAKCRC7dyhM23N6 3ncQEACgbfKyhS2517kV+J7FpHssgHj7Rygm8NrV8N5J7SOsbyW+HRGFXlgKDnhQDtPBudPIBVZ OE9cMlTY9fosxPgbImZkFWE+vlmF+QqifXjZefrELyzf3tCUSjtjtZekaG0bnMYhV9C+hrY6Nzx sW8PqqvojO/K9gv2VwiRxxQeOAKIszRGmN5LTSspgWzuF5naOjpcmm1rCxOF+JiAIFV/hwoiTuU gjjmBJ5g399kqOVojt7HYwJNfaGZWNr2sN+4M2kGj96qrHywiiqMmrrSGGFGxF35IBS3Ig1adwv x/pSGDuIuMbRIRzKFG9dUrkH5zRZ996/ity7qUWlvMV2NwbLksAhBk2HHwNaRc8M7MMajozxXcu TTtlRs6NW32cyUeFto+jL2cvy/QTqsMLhdI5AlXfeeGg841aS/RkXrqzv6I2GfuC0Tye58sBqSq 0sD9FO8rjs2BFk3/vvHC+eW9Sp+4cHdKUmzWZbMdNVm/lsxr1IORJ+KX1Uze1bUZygyw/fwxVlJ PPtA91LH8LHevlsl788x/UwHy333pjf5Gnsh+e65Zo32G+JgZRu07M13ezaKwedNnUbc3UBbrSK 2Oa63/ineiN0LroMqW6BzWWaBs3OpxlfVE3q0s/El8aZZ/IFvsehoYInkOCYPVGqy4DjaxpgxNI L++MONdyV7GQ6+g== X-Developer-Key: i=pasha.tatashin@soleen.com; a=openpgp; fpr=CAAAB722DD22A081F0D49F35633A6A993D43B569 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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. Signed-off-by: Pasha Tatashin --- kernel/liveupdate/luo_file.c | 61 +++++++++++++++++++++--------------- 1 file changed, 35 insertions(+), 26 deletions(-) diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c index 5acee4174bf0..6a0ae29c6a24 100644 --- a/kernel/liveupdate/luo_file.c +++ b/kernel/liveupdate/luo_file.c @@ -112,6 +112,7 @@ #include #include "luo_internal.h" =20 +static DECLARE_RWSEM(luo_file_handler_lock); static LIST_HEAD(luo_file_handler_list); =20 /* 2 4K pages, give space for 128 files per file_set */ @@ -277,10 +278,12 @@ int luo_preserve_file(struct luo_file_set *file_set, = u64 token, int fd) goto err_fput; =20 err =3D -ENOENT; - list_private_for_each_entry(fh, &luo_file_handler_list, list) { - if (fh->ops->can_preserve(fh, file)) { - err =3D 0; - break; + scoped_guard(rwsem_read, &luo_file_handler_lock) { + list_private_for_each_entry(fh, &luo_file_handler_list, list) { + if (fh->ops->can_preserve(fh, file)) { + err =3D 0; + break; + } } } =20 @@ -777,10 +780,12 @@ int luo_file_deserialize(struct luo_file_set *file_se= t, bool handler_found =3D false; struct luo_file *luo_file; =20 - list_private_for_each_entry(fh, &luo_file_handler_list, list) { - if (!strcmp(fh->compatible, file_ser[i].compatible)) { - handler_found =3D true; - break; + scoped_guard(rwsem_read, &luo_file_handler_lock) { + list_private_for_each_entry(fh, &luo_file_handler_list, list) { + if (!strcmp(fh->compatible, file_ser[i].compatible)) { + handler_found =3D true; + break; + } } } =20 @@ -850,25 +855,27 @@ int liveupdate_register_file_handler(struct liveupdat= e_file_handler *fh) if (!luo_session_quiesce()) return -EBUSY; =20 - /* 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' alread= y registered.\n", - fh->compatible); - err =3D -EEXIST; + scoped_guard(rwsem_write, &luo_file_handler_lock) { + /* 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' alrea= dy registered.\n", + fh->compatible); + err =3D -EEXIST; + goto err_resume; + } + } + + /* Pin the module implementing the handler */ + if (!try_module_get(fh->ops->owner)) { + err =3D -EAGAIN; goto err_resume; } - } =20 - /* Pin the module implementing the handler */ - if (!try_module_get(fh->ops->owner)) { - err =3D -EAGAIN; - goto err_resume; + 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); } - - 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); luo_session_resume(); =20 liveupdate_test_register(fh); @@ -909,10 +916,12 @@ int liveupdate_unregister_file_handler(struct liveupd= ate_file_handler *fh) if (!luo_session_quiesce()) goto err_register; =20 - if (!list_empty(&ACCESS_PRIVATE(fh, flb_list))) - goto err_resume; + scoped_guard(rwsem_write, &luo_file_handler_lock) { + if (!list_empty(&ACCESS_PRIVATE(fh, flb_list))) + goto err_resume; =20 - list_del(&ACCESS_PRIVATE(fh, list)); + list_del(&ACCESS_PRIVATE(fh, list)); + } module_put(fh->ops->owner); luo_session_resume(); =20 --=20 2.53.0.851.ga537e3e6e9-goog